UNIVERSITY OF GHANA 
 
 
 
 
 
 
DIET AND LEVELS OF TWO ENDOGENOUS ANTIOXIDANTS, 
SUPEROXIDE DISMUTASE AND CATALASE, IN THE BLOOD OF 
SEVENTH-DAY ADVENTIST VEGETARIANS AND NON-
VEGETARIANS IN MAYERA AND DANSOMAN IN THE  
GREATER ACCRA REGION OF GHANA. 
 
 
BY 
 
 
BOADIWAA OFORI-AMANFO 
(10396481) 
 
 
 
 
 
 
THIS THESIS IS SUBMITTED TO THE UNIVERSITY OF GHANA, 
LEGON IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR 
THE AWARD OF MASTER OF SCIENCE DEGREE IN DIETETICS 
 
 
 
 
 
 
 
  
JULY, 2015
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DECLARATION 
I, Boadiwaa Ofori-Amanfo, hereby declare that with the exception of references cited, 
which have been duly acknowledged, this dissertation was done by me under the 
supervision of Prof. George Asare (Maj. Rtd.) and Dr. Matilda Asante. 
 
 
………………….........      
OFORI-AMANFO BOADIWAA    DATE………………….. 
(STUDENT) 
 
 
……………………….      
PROF. GEORGE ASARE (Maj. Rtd.)   DATE……………………. 
(CO-SUPERVISOR)      
 
 
……………………….        
DR. MATILDA ASANTE    DATE…………………… 
(PRINCIPAL SUPERVISOR) 
 
 
 
 
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ABSTRACT 
Background: Vegetarianism is a dietary lifestyle that involves the restriction of diet, 
disallowing some or all foods of animal origin, thereby consuming mainly foods of plant 
origin.  Vegetarian diets are composed of only plant products which include fruits and 
vegetables, as well as grains, legumes, nuts and seeds. The plant products they consume 
are rich sources of vitamins such as Vitamins A, C and E which act directly as 
antioxidants, as well as protein and minerals such as zinc, iron, magnesium and selenium, 
which function as co-factors for antioxidant enzymes, synthesized in the body. Free 
radicals cause cell damage and have been found to be an  important contributory factor in 
the occurrence of diseases such as brain dysfunction, cancer, cardiovascular diseases. 
Little data exists on dietary composition and serum levels of endogenous antioxidants of 
vegetarians in Ghana. 
Objectives: The aim of the study was to compare the diet and serum and plasma levels of 
two common intracellular antioxidants in Seventh - day Adventist vegetarians and non-
vegetarians in Mayera and Dansoman, in the Greater Accra region of Ghana. 
Methodology: A case – control study was carried out involving 39 vegetarians and 30 
non-vegetarians. Blood pressure and anthropometric measurement (weight, height, 
visceral fat and body fat) was measured for all the participants. A structured 
questionnaire was used to obtain socio- demographic data of the participants. Dietary 
intake was assessed using a 24-hour recall and food frequency questionnaire. Venous 
blood samples were collected to assess serum and plasma levels of the endogenous 
antioxidants, catalase and superoxide dismutase. 
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Results: The mean age of vegetarians and non-vegetarians was 36.1± 8.2 and 30.7± 7.6 
years, respectively. The mean age between both groups was significantly different 
(p=0.007). Systolic blood pressure was significantly higher in vegetarians compared to 
non-vegetarians (p =0.049). There was a significant difference in the mean serum level of 
superoxide dismutase between vegetarians and non-vegetarians (p=0.044). However, 
there was no significant difference in the mean plasma level of catalase between both 
groups (p=0.075). Mean intake of protein was significantly different between both groups 
(p=0.001), whilst significant difference was found in the intake of the antioxidant 
micronutrient Vitamin E (p=0.006). Mean dietary zinc intake was significantly lower in 
the vegetarian group (p=0.000), compared to the non-vegetarian group. Dietary vitamin C 
intake in vegetarians showed a significant moderate positive correlation with SOD levels 
(p=0.04). 
Conclusion: Significantly high intake of dietary vitamin E in vegetarians could account 
for the significantly higher mean level of superoxide dismutase in this group. 
Comparatively higher intakes of Vitamins A and C in vegetarians, though not significant, 
could account for the higher levels of endogenous antioxidants in blood. There is 
therefore the need to examine more enzymatic antioxidants as well as to quantify dietary 
antioxidants. 
 
 
 
 
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DEDICATION 
This work is dedicated to my Heavenly Father, Jehovah the Almighty God, to my parents 
and to my grandmother as appreciation for their love, protection, spiritual and financial 
support throughout my life.  
 
 
  
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ACKNOWLEDGEMENTS 
I am very grateful to God for the knowledge, skill and strength with which He graced 
upon me to carry out this research project. The journey has not been easy but His Word 
has always been my encouragement and peace. 
 
 I am also most grateful to my Supervisors, firstly, Prof. George Asare (Maj. Rtd.) for his 
enthusiasm, dedication and motivation towards my research work, and secondly to Dr. 
Matilda Asante for her admirable knowledge and insightful contribution to this work. 
 
My sincerest gratitude goes to my parents and grandmother, for their unwavering love, 
care, prayers and immense financial support throughout my life. To my siblings, 
Kwadwo Boateng, Amma Serwaa and Kofi Amoako, and my Uncle, Dr. Eric Adjei of 
CSIR, I would like to say a big thank you for your love, support and encouragement. 
 
Special thanks go to Michael Ansah-Nyarko and my sister Amma Serwaa for their 
dedication during the analysis of data, to the staff and research assistants of the Chemical 
Pathology Laboratory of the School of Biomedical and Allied Health sciences for their 
contribution to this work, and to Pastor Class-Peters of the New Life Historic Seventh-
Day Adventist church and members of the congregation for agreeing to be part of this 
research.  
Finally, my heartfelt gratitude goes to Mr. David Amoako-Kusi for his love, emotional 
and spiritual support that encouraged me during the final part of this research project.  
 
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TABLE OF CONTENTS 
DECLARATION I 
ABSTRACT ii 
DEDICATION                                                                                                                    iv 
ACKNOWLEDGEMENTS                                                           v 
TABLE OF CONTENTS                                                                                                    vi  
LIST OF FIGURES ix 
LIST OF TABLES x 
LIST OF ABBREVIATIONS                                                                                            xi  
CHAPTER ONE 1 
1.0 INTRODUCTION 1 
1.1 BACKGROUND 1 
1.2 STATEMENT OF THE PROBLEM 3 
1.3 SIGNIFICANCE OF THE STUDY 4 
1.4 HYPOTHESES 4 
1.5 AIM OF THE STUDY 5 
1.6 OBJECTIVES 5 
CHAPTER TWO 6 
2.0 LITERATURE REVIEW 6 
2.1 INTRODUCTION 6 
2.2 DEFINING VEGETARIANISM 6 
2.3 TYPES OF VEGETARIANS 8 
2.4 REASONS FOR VEGETARIANISM 9 
2.5 HEALTH BENEFITS OF A VEGETARIAN DIET 9 
2.5.1    High Intakes of Certain Micronutrients 9 
2.5.2    Favourable Anthropometry and Reduced Risk of Associated Diseases 10 
2.5.3    Favourable Results in Lipid Profile 10 
2.5.4    Reduction in the Risk of Cancers and Other Degenerative Diseases 11 
2.5.5    Extension of Life Expectancy Due To Beneficial Lifestyle Behaviours 12 
2.5.6    Maintenance of Normal Blood Pressure 13 
2.6 HEALTH PROBLEMS ASSOCIATED WITH A VEGETARIAN DIET 13 
2.6.1 Vitamin B12 Deficiency, High Homocysteine Levels and Risk of Some Non-
communicable diseases 13 
2.6.2    Zinc deficiency 14 
2.7 MACRONUTRIENT INTAKE OF VEGETARIANS 15 
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2.7.1    Energy Intake 15 
2.7.2    Carbohydrate 15 
2.7.3    Protein 16 
2.7.4    Lipids (Fats) 18 
2.8 MICRONUTRIENT INTAKE OF VEGETARIANS 19 
2.8.1    Iron  19 
2.8.2    Zinc  21 
2.8.3    Vitamin C 22 
2.8.4    Vitamin E 23 
2.9 REACTIVE OXYGEN SPECIES (ROS) AND OXIDATIVE STRESS 24 
2.10     DIET AND ANTIOXIDANT LEVELS 28 
2.11     ANTIOXIDANT PROTECTION 29 
2.11.1  Superoxide Dismutase (SOD) 31 
2.11.2  Catalase (CAT) 32 
2.12     FRUITS AND VEGETABLES 33 
2.13     CEREALS AND GRAINS 33 
2.14     LEGUMES, SEEDS AND NUTS 34 
CHAPTER THREE 36 
3.0 MATERIALS AND METHODS 36 
3.0 STUDY DESIGN 36 
3.1 STUDY SITES 36 
3.2 SUBJECT RECRUITMENT 36 
3.3 SAMPLE SIZE DETERMINATION 37 
3.4 SUBJECT SELECTION 38 
3.4.1    Inclusion Criteria 38 
3.4.2    Exclusion criteria 38 
3.5 ETHICAL APPROVAL 38 
3.6 PRE-TESTING OF QUESTIONNAIRE 38 
3.7 DATA COLLECTION 39 
3.8 ANTHROPOMETRIC MEASUREMENT 39 
3.8.1    Weight 39 
3.8.2    Height 40 
3.8.3    Visceral Fat and Body Fat Percentages 40 
3.9       BLOOD PRESSURE MEASUREMENT 41 
3.10     DIETARY INTAKE ASSESSMENT 41 
3.11     BLOOD SAMPLE COLLECTION AND HANDLING 41 
3.12     SAMPLE PREPARATION AND STORAGE 42 
3.13     BIOCHEMICAL ANALYSIS 42 
3.13.1  Superoxide Dismutase (SOD) 42 
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3.13.2  Reagents 43 
3.13.3  Preparation of Standards 43 
3.13.4  Sample Preparation 44 
3.13.5  Assay Procedure 44 
3.13.6  Catalase 45 
3.13.7  Reagents 45 
3.13.8  Preparation of Standards 46 
3.13.9  Assay Procedure 46 
3.14     DATA PROCESSING AND ANALYSIS 46 
CHAPTER FOUR 48 
4.0 RESULTS 48 
4.1 SOCIO- DEMOGRAPHIC CHARACTERISTICS OF PARTICIPANTS. 48 
4.2 VEGETARIANISM 49 
4.2.1    Types and reasons for choice of vegetarianism 49 
4.3 DIETARY HABITS AND MEAL PATTERNS OF PARTICIPANTS 51 
4.4 LIFESTYLE BEHAVIOURS 52 
4.5 ANTHROPOMETRIC AND BLOOD PRESSURE PARAMETRES OF PARTICIPANTS 53 
4.6 FREQUENCY OF FOOD CONSUMPTION 54 
4.6.1    Animal protein and vegetable protein 54 
4.6.2    Fruits, Vegetables, Fruit juices and Soft Drinks 55 
4.6.3    Tubers, Cereals and Grains 56 
4.6.4    Fast foods, deep fried foods and pastries 57 
4.7 ENERGY AND NUTRIENT INTAKES 58 
4.7.1    Macronutrient intake in vegetarians and non-vegetarians 58 
4.7.2    Mean daily intake of antioxidant vitamins and selected micronutrients 59 
4.8 BIOCHEMICAL ANALYSIS 60 
4.9 RELATIONSHIP BETWEEN YEARS OF VEGETARIANISM AND SERUM AND PLASMA 
LEVELS OF ENDOGENOUS ANTIOXIDANTS 63 
CHAPTER FIVE 64 
5.0     DISCUSSION AND CONCLUSION 64 
5.1 DISCUSSION 64 
5.2 LIMITATIONS OF THE STUDY 73 
5.3 CONCLUSIONS 74 
REFERENCES 76 
APPENDIX I 100 
APPENDIX II 102 
 
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LIST OF FIGURES 
Figure 3.1: Body fat ranges for adults 40 
Figure 4.1: Reasons for becoming a vegetarian 50 
Figure 4.2: Years of Vegetarianism 51 
Figure 4.3: Comparison of frequency of  intake of animal protein and vegetable  
                    protein in vegetarians and non-vegetarians 55 
Figure 4.4: Comparison of frequency of  intake of vegetables, fruits, fruit juices   and                          
soft drinks/sweets in vegetarians and non-vegetarians 56 
Figure 4.5: Comparison of frequency of  intake of tubers, cereals and grains 57 
Figure 4.6: Comparison of frequency of intake of fast foods, pastries and deep fried 
                   foods   58  
Figure 4.7: Mean serum levels of Superoxide dismutase in vegetarians and non- 
vegetarians 61 
Figure 4.8: Mean plasma levels of catalase in vegetarians and non-vegetarians 62 
 
 
 
 
 
 
 
 
 
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LIST OF TABLES 
Table 4.1: Socio-demographic characteristics of participants 49 
Table 4.2: Dietary habits and meal patterns of participants 52 
Table 4.3: Lifestyle behaviour of participants 53 
Table 4.4:  Comparison of anthropometric and blood pressure                                 
measurement between vegetarians (V) and non-vegetarians (NV) 54 
Table 4.5: Macronutrients intake in vegetarians and non-vegetarians 59 
Table 4.6:  Micronutrients and dietary antioxidant intake in                                    
vegetarians and non-vegetarians 60 
Table 4.7:  Correlation between intake of dietary antioxidants and                                 
serum (SOD) and plasma (catalase) enzymatic antioxidant levels 62 
Table 4.8: Correlation between years of vegetarianism and                                            
serum and plasma levels of endogenous antioxidants 63 
 
  
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LIST OF ABBREVIATIONS 
AND  - Academy of Nutrition and Dietetics 
BMI  - Body Mass Index 
CAT  - Catalase 
DNA  - Deoxyribonucleic acid 
EPIC  -  European Prospective Investigation into Cancer and Nutrition 
MUFA  - Mono unsaturated fatty acid 
NV   - Non-Vegetarians 
PUFA  - Poly unsaturated fatty acid 
ROS  - Reactive Oxygen Species 
SFA  - Saturated Fatty Acid 
SOD  - Superoxide Dismutase 
V  - Vegetarians 
WHO  - World Health Organisation 
 
 
 
 
 
 
 
 
 
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CHAPTER ONE 
1.0 INTRODUCTION 
1.1 Background
According to Dorland’s Medical Dictionary for health consumers (2007), vegetarianism 
is a dietary lifestyle that involves the restriction of diet, disallowing some or all foods of 
animal origin, thereby consuming mainly foods of plant origin. People choose to adopt a 
vegetarian lifestyle due to reasons such as concern about the environment, animal 
welfare, health concerns and religious beliefs (British Dietetic Association, 2011).  
 
Vegetarians’ main source of protein and other important micronutrients such as vitamin 
B12, zinc and iron are from plant products, mostly fruits, legumes and vegetables. 
Although the vegetarian’s diet can provide enough protein if a variety of the protein-rich 
plant products are consumed, the protein quality from plant sources is low compared to 
that from animal sources (Messina and Messina, 1996). Research also shows that vegans 
(strict vegetarians) usually have low intakes of calcium and vitamin B12 (Davey et al., 
2003). As a result, assumptions have been made about the adequacy of a vegetarian diet 
in providing the recommended daily allowance of protein, calcium and vitamin B12. 
However, the Academy of Nutrition and Dietetics (2009) has stated in its position paper 
that; “appropriately planned vegetarian diets, including total vegetarian or vegan diets, 
are healthful, nutritionally adequate, and may provide health benefits in the prevention 
and treatment of certain diseases. 
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Studies in the area of nutritional assessment and the function of dietary components of 
food in the body have found that plant foods are a rich natural source of antioxidants, as 
well as vitamins and minerals (Hamid et al., 2010). 
 
Antioxidants are substances that may protect cells from the damage caused by unstable 
molecules known as free radicals which are produced as a result of oxidation reactions 
(Hamid et al., 2010).  
 
Free radicals are formed in the body as a result of conditions such as exposure to cigarette 
smoke, stress, pollution, illness and even exercise (Hamid et al., 2010). Also, utilization 
of oxygen by the body results in protein, fat and carbohydrate metabolism (Kumar et al., 
2012). 
 
Free radicals cause cell damage and have been found to be an  important contributory 
factor in the occurrence of diseases such as brain dysfunction, cancer, cardiovascular 
diseases, as well as in the process of ageing. The function of antioxidants in the body is to 
deactivate free radicals before they attack cells (Somannavar and Kodliwadmath, 2012). 
 
Total vegetarian diets are composed of only plant products which include fruits and 
vegetables, as well as grains, legumes, nuts and seeds. The plant products the consumed 
are rich sources of vitamins such as vitamins A, C and E which act directly as 
antioxidants, as well as protein and minerals such as zinc, iron, magnesium and selenium, 
which function as co-factors for antioxidant enzymes synthesized in the body.  
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Thorough studies into antioxidants, such as vitamin C and E, beta carotene and other 
carotenoids, polyphenols, as well as endogenous antioxidants such as glutathione 
peroxidase and superoxide dismutase, have shown that their actions in the body 
contribute greatly to the prevention of degenerative processes and diseases such as 
ageing, cardiovascular diseases, and cancer, which come about as a result of tissue 
damage (Gupta and Sharma, 2006). 
 
Stanner et al. (2004) found that a lower risk of heart disease and some neurological 
diseases was recorded in individuals who consumed fruits and vegetables.  
 
1.2 Statement of the problem 
Most daily occurrences and processes such as exercise, stress, illness, drug intake and 
pollution result in an increase in free radical exposure. Free radicals have been shown to 
be a part of the pathogenesis of at least 50 diseases (Halliwell, 1994). Even beneficial 
processes such as the oxidation of fats, proteins and carbohydrates, which make use of 
oxygen, result in the exposure to free radicals. This exposure is believed to be of very 
great significance when it comes to the process of ageing, as well as in the pathogenesis 
of diseases such as cancer and cardiovascular disease, both of which have gradually 
become the leading causes of death, in recent years (WHO, 2007). As a result of this 
exposure, antioxidants, which serve as the first line of defense against the action of free 
radicals, and which can be obtained through the foods we eat, become very necessary for 
the body in order to maintain the integrity of cells and prevent tissue damage. 
 
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Due to the dietary habits of vegetarians, it is assumed that they consume more fruits and 
vegetables in their diet and are most likely to have a better antioxidant status. However 
there is minimum literature on the dietary intake of vegetarians in Ghana. There is also 
minimum information to ascertain whether vegetarians in Ghana consume adequate 
amount of fruits, nuts, legumes, grains, cereals and vegetables to show distinct difference 
in their antioxidant levels as compared to non-vegetarians. 
 
1.3 Significance of the Study 
This study will help to determine whether a vegetarian diet, through the provision of 
antioxidants, has the ability to provide the best protection and action against free radical 
formation and their destructive action in cells and tissues. The results obtained will assist 
in making recommendations to individuals who generally want to consume a healthy diet, 
as part of a healthy lifestyle, or to individuals suffering from disease conditions in which 
free radicals play an important role. 
 
1.4 Hypotheses 
1. Vegetarians have significantly higher blood levels of superoxide dismutase than 
non-vegetarians. 
2. Vegetarians have significantly higher plasma levels of catalase than non-
vegetarians. 
3. There is a significant relationship between intake of antioxidant vitamins and 
levels of superoxide dismutase in serum and catalase in plasma among 
vegetarians and non-vegetarians. 
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1.5  Aim of the Study 
The aim of the study was to compare dietary intake and levels of two common 
endogenous antioxidants, superoxide dismutase and catalase in 7th Day Adventist 
vegetarians and non-vegetarians in Mayera and Dansoman in the Greater Accra region. 
 
1.6 Objectives 
The specific objectives of the study were: 
1. To assess and compare the nutrient intakes of the vegetarians and non-
vegetarians. 
2. To compare frequency of consumption of food among the vegetarians and non-
vegetarians. 
3. To determine intakes of selected dietary antioxidants (vitamin A, C and E) and 
their relationship with levels of the endogenous antioxidants, superoxide 
dismutase and catalase among the vegetarians and non-vegetarians. 
  
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CHAPTER TWO 
2.0 LITERATURE REVIEW 
 
2.1 Introduction 
Vegetarianism before the 19th century, (though the term was coined during the period), 
was a decision, justified on the basis of metaphysical and moral arguments (Whorton, 
1994). According to Whorton (1994), vegetarianism is a lifestyle that began in the early 
1800s, usually among some philosophers.  The idea of vegetarianism, being a lifestyle 
that promoted non-violence against animals (Kerry et al., 2001) was earlier recorded 
among a number of people in ancient India and ancient Greek civilizations (Spencer, 
1993). According to Passmore (1975) although vegetarianism almost disappeared from 
Europe in the 4th to 6th centuries, the renaissance in Europe saw a re-emergence of the 
practice (Spencer, 1993), leading to its practice among a wider group of people in recent 
years. Vegetarianism was even justified with a bible reference from Genesis 1:29, 
showing that the vegetarian diet had its origination from God, and that was the diet 
expected of humans for consumption (Smith, 1983). 
 
2.2  Defining Vegetarianism 
According to the Dorland’s Medical Dictionary (2007), a vegetarian is an individual who 
does not eat meat fish, poultry, game, any form of shellfish, or products derived from any 
of these sources. The society also gave a second definition which describes a vegetarian 
as an individual who lives on plant-based diets of grains, vegetables, fruits, pulses, nuts 
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and seeds, either or not,  exempting dairy product and eggs. Stahler’s study (2005) on the 
number of adolescent vegetarians in the United States (U.S.) showed 3% of 8-18 year 
olds being vegetarians, with close to 1% following a strict vegan diet. A nationwide poll 
carried out in the United States in 2006 revealed that approximately 2.3% of the adult 
population never consumed meat, fish or poultry, emphasizing their consistency in 
following a vegetarian diet (Stahler, 2006). 
 
Due to the dietary habit of excluding flesh meat in meals, as well as dairy products and 
eggs, research has shown that vegans (strict vegetarians) usually have low intakes of 
calcium and vitamin B12 (Davey et al., 2003). Also, although the vegetarian’s diet could 
provide enough protein if a variety of the protein-rich plant products are consumed, the 
protein quality from plant source is low, compared to that from animal sources (Messina 
and Messina, 1996). As a result, assumptions were made about adequacy of a vegetarian 
diet in providing the recommended daily allowance of protein, calcium and vitamin B12. 
However, the Academy of Nutrition and Dietetics (2009) has stated in its position paper 
that “appropriately planned vegetarian diets, including total vegetarian or vegan diets, are 
nutritionally adequate, and may provide health benefits in the prevention and treatment of 
certain diseases.   
 
If an adult vegetarian diet is well planned, involving choices from a variety of 
nutritionally adequate foods, it is possible for the individual to receive sufficient nutrients 
and calories necessary to support a healthy life (Academy of Nutrition and Dietetics, and 
Dietitians of Canada, 2003). On the other hand, studies by Ambroszkiewicz et al. (2006; 
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2007) suggests that because of the inability of children to consume sufficient food at a 
time and throughout the day, it is difficult for them to meet their nutritional needs from a 
vegetarian or vegan diet. 
 
2.3  Types of Vegetarians 
Although generally, vegetarians have a lifestyle of abstaining from anything associated 
with the “exploitation” of animal, there are variations in the lifestyle, ranging from 
flexible to extremely strict vegetarians. According to Robinson and Hackett (1995), 
vegetarian diets can be classified into the following: 
 
Vegan: Avoids intake of every food derived from animals. 
Lacto-ovo-vegetarian: Avoids all animal flesh but consumes milk and eggs. 
Ovo-vegetarian: Avoids consumption of all animal flesh and milk, but consumes eggs. 
Lacto-vegetarian: Includes dairy products in diet, avoids all flesh foods and eggs. 
Pesco-vegetarian: Includes fish (and possibly other seafood). May include dairy 
products and eggs, but totally avoids meat and poultry. 
Demi-vegetarian (semi-vegetarian): Occasionally consumes meat/poultry/fish. 
Fruitarian: This individual goes an extra mile to be concerned about the life of the 
plants from which meals are obtained. As a result, the diet generally consists only of 
foods that do not kill the plant of origin. Foods consumed include fresh and dried fruits, 
nuts, seeds and a few vegetables. Additionally, an individual can fall under the category 
of a vegetarian if meat, fish or poultry is consumed less than once a week (Sabate et al., 
2001). 
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2.4 Reasons for Vegetarianism 
Studies have shown that for a majority of people around the world, mostly from 
developing countries, economic and geographic reasons account for their dependence on 
plant-based diets alone (Rottka, 1990). According to Whorton (1994) recent practice of 
vegetarianism is usually attributed to moral and other non-scientific reasons as opposed 
to the earlier practice by philosophers, whose reasons were much more scientific. Sabate 
et al. (2001) pointed out many reasons why people choose to adapt vegetarianism which 
include cost, family influences, sensory and taste preferences, philosophical reasons (e.g. 
religious teachings such as Buddhism or membership of the Seventh-Day Adventists) or 
as a reaction to food safety scares, such as salmonella, bovine spongiform 
encephalopathy (BSE), Escherichia. coli, or the use of antibiotics or growth hormones in 
meat production. People also choose to adopt a vegetarian lifestyle due to reasons such as 
concern about the environment, animal welfare, health concerns and religious beliefs 
(British Dietetic Association, 2011).   
 
2.5 Health Benefits of a Vegetarian Diet 
2.5.1 High Intakes of Certain Micronutrients 
Vegetarians have been reported to have high intakes of iron, magnesium, potassium and 
copper; thus the presence of adequate amounts of these nutrients in their diets could be 
attributed to the wide variety of fruits, vegetables and plant-based diets consumed 
(Waldmann et al., 2003). According to Perry and his colleagues (Perry et al., 2002), iron 
intakes of vegans and vegetarians are almost equal to that of omnivores or sometimes 
even higher. It may be argued that since meat provides very high amounts of iron in their 
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most readily available form (the heme form), vegetarians could be deficient in adequate 
iron stores, because their source of iron is non-heme, which is sensitive to absorption 
inhibitors like phytates. However, research has shown that non-haeme iron is equally 
sensitive to absorption enhancers like vitamin C, of which vegetarians obtain adequate 
amounts from their consumption of fruits and therefore, iron intake and absorption may 
not be a problem for vegetarians if they consume plant foods from very iron-rich sources 
(Davey et al., 2003).  
 
2.5.2 Favourable Anthropometry and Reduced Risk of Associated Diseases 
Vegetarian and vegan adults have been shown to have lower body mass indices (BMI), 
usually 1-2 kg/m2 less than comparable non-vegetarians, with vegans even having a lesser 
BMI as compared to vegetarians (Appleby et al., 2002). In a study by Philips et al. 
(2004), it was observed that a change in an omnivorous diet to a vegetarian diet resulted 
in a change in anthropometric measurement towards values that favoured a lower risk of 
development of coronary heart disease (CHD). 
 
2.5.3 Favourable Results in Lipid Profile 
A study carried out by Robinson et al. (2002) has confirmed that transitioning from an 
omnivorous diet to that of a vegetarian diet produces favourable results in the lipid profile 
of an individual. Results from another study conducted in Korea to compare the lipid 
profile of vegetarians and non-vegetarians, showed a significant lower level of lipids in 
vegetarians than in non-vegetarians (Kyung et al., 2012). A similar study was carried out 
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by Béderová et al. (2000) to compare nutrient intake and corresponding biochemical 
parameters in adolescent vegetarians and non-vegetarians.  Results obtained indicated a 
more favourable lipid profile in the vegetarian participants due to the consumption of less 
fat, with a higher intake of fat obtained rather from plants. The study observed not only 
lower risk parameters of artherosclerosis, but also comparatively higher values of 
antisclerotic factors in the vegetarian group. 
 
2.5.4 Reduction in the Risk of Cancers and Other Degenerative Diseases 
A significant reduction in the risk of cancers of the lungs, stomach oesophagus and 
colorectum have been reported to occur with increase in consumption of fruits and 
vegetables, according to a research carried out by Riboli and Norat (2003). In the 
European Prospective Investigation into Cancer and Nutrition (EPIC) study, evidence 
showed that consumption of dietary fibre, which can be obtained mostly from whole 
grains, fruits and vegetables, was inversely related to the development of large bowel 
cancer (Bingham et al., 2003). Allen et al. (2000) in their study to determine levels of the 
hormone, insulin-like growth factor-1 in vegan men, observed that the hormone, which is 
thought to be associated with the aetiology of several cancers, was low in vegans 
compared with lacto-ovo vegetarians and non-vegetarians, thereby conferring on them 
the advantage of a reduced risk of colorectal cancer.  
  
Not all research studies have supported these claims. Earlier research by Fraser (1999), 
who sought to establish a relationship between diet and certain degenerative diseases, his 
results showed that when gender, age and smoking was adjusted, there was no difference 
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in the risk of development of breast, prostate, lung and uterine cancers. This means that in 
the development of cancers, diet is not the only determinant, but smoking and age also 
play important roles.  
Furthermore, various studies on the relationship between vegetarianism and cancer have 
not succeeded in establishing clear differences in cancer rates between vegetarians and 
omnivores (Key et al., 2006). Also, diets that are usually soy-based may be adequate for 
individuals suffering from chronic kidney disease and could slow progression of the 
disease (Bernstein et al., 2007). 
 
2.5.5 Extension of Life Expectancy Due To Beneficial Lifestyle Behaviours 
Again, from the EPIC cohort study, a conclusion was reached that certain lifestyle 
behaviours which included not smoking, moderate alcohol intake, being physically 
active, and the consumption of at least five fruit and vegetable servings a day, all lifestyle 
behaviours of vegetarians (Key, 1999), were estimated to amount to an additional 14 
years of life (Khaw et al., 2008).  In the same study however, regular intake of processed 
meats increased the risk of cardiovascular diseases and deaths from cancer, which was 
actually observed among the non-vegetarians. 
 
However, these results also conflict with some studies done on a very large scale, 
involving large populations in other parts of the world. For example, in a typical study 
the Icelanders, Swiss, Norwegians, and the Swedes who are considered the healthiest 
people in the European continent (and with very high life expectancy), were found to 
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consume large amounts of fish, poultry and dairy products, which fall under animal 
products (Ginter, 2008).  
 
2.5.6 Maintenance of Normal Blood Pressure 
Studies have linked the consumption of vegetarian diets to favourable results for systolic 
and diastolic blood pressures. Results from the Adventist Health Study-2 (AHS-2) on the 
relationship between vegetarian diets and blood pressure showed than vegan participants 
had lower systolic blood pressure than omnivorous subjects and were less likely to be 
taking antihypertensive medications (Pettersen et al., 2012). Brathwaite et al., in 2003 
also proved this point. In their study carried out to determine the prevalence rate of 
diabetes, obesity and hypertension in vegetarian and non-vegetarian participants, they 
observed a comparatively lower prevalence rate of hypertension in long-term vegetarians 
than in non-vegetarians, with emphasis on “long term vegetarians”. 
 
2.6 Health Problems Associated With a Vegetarian Diet 
2.6.1  Vitamin B12 Deficiency, High Homocysteine Levels and Risk of Some Non-
communicable diseases 
In a study carried out by Mezzano et al. (1999) to determine the comparative levels of 
homocysteine in vegetarians and meat-eaters, it was observed that plasma homocysteine 
was 41% higher in vegetarians than comparable meat-eaters. This was attributable to 
their low serum vitamin B12 concentrations, which was reported in 21 out of 26 
vegetarians. Among vegetarians and non-vegetarians, vegans have been found to have the 
highest concentration of homocysteine in serum (Obeid et al., 2002). Research has shown 
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homocysteine to be an independent risk factor in the development of cardiovascular 
disease (Taylor et al., 2000). This shows that a vegetarian diet may not always be 
protective against the development of cardiovascular disease and therefore adequate 
supplementation and use of vitamin B12 fortified foods is required to prevent these high 
homocysteine levels from occurring in vegetarians (Herrmann, 2003). Vegetarians must 
also be advised to plan their diet very well and monitor their plasma vitamin B12 status 
regularly in order to detect early, low cobalamin status (Elmadfa and Singer, 2009).  
 
Vitamin B12 deficiency could also result in megaloblastic anaemia with symptoms which 
include abnormal sensations in the limbs, weakness or demyelination in peripheral nerves 
and the central nervous system, leading to a range of psychiatric disorders (Craig & 
Pinyan, 2001). A point worth noting however is that the visible expression of these 
symptoms may be suppressed for a while when folic acid intakes are high, and this is the 
situation observed in both vegetarians and non-vegetarians since both groups have been 
found to have adequate intakes in folate (Thomas and Bishop, 2007). 
 
2.6.2 Zinc deficiency 
A research has shown vegetarians to have low intakes of the micronutrient zinc (Li et al., 
2000). Strategies to employ in reducing zinc deficiency or improving zinc status in 
vegetarian include consumption of zinc-fortified food, zinc supplementation and dietary 
practices that increase the bioavailability of dietary zinc especially from the plant sources 
(Foster et al., 2013). These strategies, according to Foster et al. (2013) are very important 
especially in vegetarians whose serum zinc concentrations are at the lower end or below 
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that of the reference range, or in those who generally have consistent low zinc intakes 
relative to their diet. 
 
2.7 Macronutrient Intake of Vegetarians  
2.7.1 Energy Intake 
In a study that sought to analyze the dietary patterns of vegetarians and omnivores, the 
mean total energy intake was found to be comparable between the two groups at a p-
value of >0.05 (Clarys et al., 2013). This showed that energy intake between vegetarian 
and non-vegetarian subjects were almost equal. Evidence from a cohort study has shown 
that an increase in weight gain, as a result of increase in calorie intake in breast cancer 
diagnosed women, increased the mortality in the group by 13%, for each 5 kg gain in 
weight (Nichols et al., 2009). Calorie restriction has been found to result in inhibited 
accumulation of oxidatively damaged proteins in laboratory rats (Youngman et al., 1992). 
This may imply that there is a strong relationship between the amount of calories 
consumed and the production of reactive oxygen species. Sleep deprivation has been 
associated with increased consumption of calories from snacks (Nedeltcheva et al., 
2009). 
 
2.7.2 Carbohydrate 
This macronutrient provides the most readily available form of energy. Each gram of 
carbohydrate provides 4 kcal of energy to the body (Mahan et al., 2012). Main 
carbohydrate sources include cereals, grains and tubers, which both vegetarians and non-
vegetarians have no restriction on their intake. As a result, most studies (Nadimi et al., 
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2013; Shridhar et al., 2014; Clarys et al., 2013) but a few, have found no significant 
difference in the intake of carbohydrates between the two groups. In certain studies, 
intake of carbohydrates between vegetarians and non-vegetarians was not significantly 
different (Nadimi et al., 2013). However, in another study conducted to compare dietary 
pattern between vegetarians and non- vegetarians, carbohydrate and fibre intake was 
significantly higher in vegetarians than in the omnivorous subjects (Shridhar et al., 2014, 
Clarys et al., 2013). This was attributed to the fact that the vegetarians obtained their 
carbohydrates from more unrefined sources (Clarys et al., 2013). Whole grain, total 
dietary fibre and cereal fibre have shown strong inverse association with incidence of 
diabetes (Meyer et al., 2000) showing that unrefined carbohydrates are more protective 
against diabetes as compared to refined carbohydrates. 
 
2.7.3 Protein  
Biochemically, proteins are macromolecules which are made up of one or more long 
chains of amino acids. Nutritionally, proteins are one of the three important 
macronutrients needed daily by the body in specific amounts, as part of a balance. To a 
molecular biologist or biochemist, proteins are important to every human because of the 
various roles they play in various biochemical processes in the body which include 
replication of DNA, acting as transporters that move molecules from one point in the 
body to another, responding to stimuli as well as acting as enzymes that speed up 
metabolic reactions (Lodish et al., 2004). Protein is known as a building block because it 
is the main nutrient that is responsible for maintaining and growing lean muscle, through 
the action of amino acids. Another reason why proteins are so important involves the fact 
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that they repair worn-out tissues or wounds. Requirements for proteins are not the same 
for each life cycle. The Recommended Daily Allowance (RDA) for protein either at each 
stage of life of a healthy individual (whether toddler, adolescent, adult, during pregnancy 
or during lactation and old-age) or within a specific age group has been obtained as 0.8 to 
1.0 g/kg body weight/ day (Mahan et al., 2012). 
Protein is obtained from two sources, namely animal and plant sources. Examples of 
animal sources of proteins include meat (beef, mutton, and venison), egg, poultry, fish 
and milk. Plant protein can be obtained from legumes (beans and lentils), pulses and nuts 
(peanuts, cashew nuts, almonds). 
 
Since vegetarians avoid consumption of meat and or animal products they depend on 
plant sources of protein to meet their daily requirement whilst non-vegetarians obtain 
protein from animal sources as well as from plants. According to the Academy of 
Nutrition and Dietetics (2009), in their position paper on vegetarian diets, there have been 
arguments about the quality of protein from plant sources and the adequacy of protein 
obtained from a single plant source per meal. However, it has been established that 
careful planning of a vegetarian diet may provide enough protein even from a single plant 
source and may not require combinations from different plant protein sources per meal.  
 
Some studies have reported a lower relative intake of proteins in vegetarians as compared 
to non-vegetarians. A research by Clarys et al. (2013) showed that the absolute and 
relative protein intake by vegetarians was significantly lower than in non-vegetarians. In 
another study by Nadimi et al. (2013) showed that the mean intake of protein (40.45 ± 
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19.41g) by vegetarians was significantly lower (p=0.04) compared to intakes in non-
vegetarians (56.96 ± 11.94 g). 
 
2.7.4  Lipids (Fats) 
Four main types of fat make up the fats found in the food we eat, and these are grouped 
into healthy and unhealthy fats. These types are monounsaturated fats, polyunsaturated 
fats (omega 6 and omega 3 fats) referred to as healthy fats, and the unhealthy fats namely 
saturated fats and trans fat (Mayo Clinic, 2014). Examples of monounsaturated fats are 
olive oil, canola oil, avocados and oils found in nuts and seeds. Examples of 
polyunsaturated fats include safflower oils, sesame and sunflower oils, which fall under 
omega 6 fats and oils from fatty fish, flaxseed and soybean, which fall under omega 3 oils 
(Heart and Stroke Foundation, 2010). Saturated fats on the other hand are obtained from 
animal sources of food, whilst trans fat are obtained from oils that go through partial 
hydrogenation, which makes cooking with them easier. Trans fats are found in snacks 
and fast foods. 
 
A study was carried to examine the change in total fat intake and plasma lipid levels 
when saturated fat was replaced with polyunsaturated and monounsaturated fat. The 
results showed that fat intake decreased by 5.1% energy and 2.9% energy when saturated 
fat was replaced with monounsaturated and polyunsaturated fat, respectively (Hodson et 
al., 2001). The same study recorded lower plasma total cholesterol, low-density 
lipoprotein and high-density lipoprotein by 19%, 22% and 14%, respectively, when 
saturated fat was replaced by polyunsaturated fat. A study has also shown that replacing 
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saturated fat by polyunsaturated or monounsaturated fat lowers both low density 
lipoproteins (LDL) and high density lipoproteins (HDL) (Siri-Tarino et al., 2010).  
 
In a study to determine nutrient intake of vegetarian and non-vegetarian women, 
vegetarian participants recorded a higher ratio of polyunsaturated fat to saturated fat 
intake than their non-vegetarian counterparts. (Janelle and Barr, 1995). Another study 
however has recorded similar intake of polyunsaturated fat between vegetarian and non-
vegetarian groups (Dourado et al., 2011). Nadimi et al. (2013) in a study to determine the 
association of vegan diet with body composition and oxidative stress found no significant 
difference in fat intake between the two groups. A study carried out in the United States 
by Haddad and Tanzman (2003) found that the vegetarian participants had lower intakes 
of total fat, saturated fat and cholesterol, compared with the non-vegetarian participants. 
 
2.8 Micronutrient intake of vegetarians 
2.8.1 Iron 
Iron is a very important micronutrient that is obtained naturally in food. There are two 
forms, from which iron is obtained, namely haeme iron, obtained from animal sources 
and non- heme iron, obtained from plant sources. Iron forms part of haemoglobin and 
myoglobin. These are proteins that help in the transport and transfer of oxygen from the 
lungs, where exchange of oxygen takes place, to tissues and muscles, respectively 
(Agget, 2012). Associations have been recorded between serum homocysteine and 
markers of iron deficiency, in which significantly higher serum homocysteine levels have 
been reported in individuals with iron deficiency anaemia (Sirdah et al., 2014). Children 
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who consume iron-deficient diet and those with iron deficiency anaemia have been found 
to show poor cognitive development. Supplementation with iron tends to produce 
remarkable improvement in motor and language capabilities in children (Stoltzfus et al., 
2001). Effects of a vegetarian diet on iron status depend on the bioavailabilty of iron from 
plant foods rather than the amount of total iron in the diet (Venderley and Campbell, 
2006). 
 
Iron intakes were found to be equal among vegetarians and non-vegetarians in a study 
conducted by Ball and Bartlett (1999), although vegetarians recorded slightly higher 
intake of iron. The highest percentage of the iron consumed in vegetarian participants, 
were obtained from cereals and cereal products, followed by vegetables, then breakfast 
cereals, and the lowest percentage from fruits. Recent studies however have produced 
different outcomes. For example, in the EPIC-Oxford study by Davey et al. (2003) that 
examined the lifestyle characteristics and nutrient intakes between the two groups, the 
highest intake of iron was recorded among the vegan group. Li et al. (2000) as well 
recorded higher iron intakes in vegetarians than in non-vegetarians in their study that 
sought to determine micronutrient intake in vegetarian and vegan men, as well as in men 
with different meat intakes. However, serum ferritin levels in vegetarians have been 
found to be significantly lower than in non-vegetarians, the result being attributed to the 
reduced bioavailability of the iron derived from plant sources (Ball and Bartlett, 1999; Li 
et al., 2000). 
 
 
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2.8.2 Zinc  
Zinc is one micronutrient that has generated lots of questions about its availability and 
adequacy in vegetarian diets. Plant sources of zinc include nuts, legumes and whole 
grains. These are very good sources of the micronutrient. However zinc found in plants 
has reduced bioavailability, as a result of the binding of phytates to it, and hereby, 
making absorption difficult (Cena et al., 2008). The RDA for zinc for adult men and 
women is 11 mg and 8 mg respectively (Academy of Nutrition and Dietetics, 2009). 
According to the Academy of Nutrition and Dietetics, whole grain products usually have 
higher zinc content as compared to refined grains and so even in the presence of phytate, 
relatively more zinc is absorbed from whole grain products than refined products. 
Requirements for zinc in vegetarians whose diets most of the time consists of phytate-
rich sources may exceed the recommended dietary intake. 
 
Recommendations on meeting zinc needs for individuals on plant-based diets include 
increasing zinc bioavailability by soaking dried beans in water and discarding the water 
prior to cooking, using fermented soy products, selecting whole grain cereals instead of 
refined alternatives and putting emphasis on zinc-rich foods such as nuts legumes, whole 
grains and avoiding the intake of calcium supplements before or after consuming foods 
that are rich in zinc (Messina et al., 2004). 
 
In a review paper that sought to bring together information on results of various studies 
carried out on zinc status of vegetarians, the summary revealed that out of the 34 research 
works reviewed, 26 assessed and compared male and female vegetarians with non-
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vegetarian subjects and recorded that dietary zinc intakes and zinc concentration in serum 
was significantly lower in individuals that habitually followed vegetarian diets than 
omnivorous diets (Foster et al., 2013). Vegans have been found to have the lowest intake 
of zinc in a comparative study that assessed dietary intake among meat-eaters, fish-eaters, 
lacto-ovo vegetarians and vegans (Davey et al., 2003). Meat-eaters in a different study 
recorded higher intakes of zinc than did their vegetarian and vegan counterparts (Li et al., 
2000). Others however have observed that dietary zinc intake between both groups are 
comparable (Rauma and Mykkanen, 2000). 
 
2.8.3 Vitamin C 
One indispensable micronutrient and antioxidant vitamin is Vitamin C, found mostly in 
fruits and vegetables. Water-soluble vitamin C is one antioxidant vitamin capable of 
neutralizing hydrogen peroxide, superoxide radical and hydroxyl radical, which are all 
reactive oxygen species (ROS) (Percival, 1998). A very important role played by Vitamin 
C in a vegetarian diet is its ability to act as an efficient iron-absorption enhancer. Vitamin 
C increases and facilitates the absorption of non-haeme iron obtained from plant sources, 
whose absorption is usually inhibited by absorption inhibitors like phytates (Davey et al., 
2003). 
 
 Vegetarians reported higher intake of vitamin C than their non-vegetarian counterparts in 
earlier studies by Janelle and Barr 1995 (in a study carried out in a Metropolitan area in 
Canada) and Harmann and Parnell, 1998 (New Zealand). In the EPIC-Oxford study, 
vegetarians again recorded the highest intake of vitamin C (Davey et al., 2003). A more 
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recent study on vegetarian dietary intake also ended up with similar results. In the study 
conducted by Shridhar et al. (2014), although non-vegetarians reported higher intake of 
fruits, vegetarians still showed higher intake of dietary Vitamin C with an observed 
higher intake of vegetables. In a study conducted to determine the protective plasma 
value of vitamin C in an adult population of vegetarians and non-vegetarians from 
Slovakia, it was observed that 88% of the vegetarian participants had optimum protective 
value as opposed to the non-vegetarian participants who had only 46% of their 
participants having an optimum protective value (Krajčovičová-Kudláčková et al., 2007). 
Therefore, taking into consideration most research work on vegetarian versus non-
vegetarian diet, as well as an article that discussed antioxidant status in vegetarian and 
omnivorous diet, it will be efficient to conclude that a vegetarian diet helps in the 
maintenance of an optimum antioxidant vitamin status. 
 
2.8.4 Vitamin E 
Vitamin E is another important antioxidant vitamin responsible for neutralizing the effect 
of free radicals, mostly lipid peroxides and hydrogen peroxides, in the body (Percival, 
1998). Rich sources of fat-soluble vitamin E include whole grains, nuts, seeds, plant oils, 
avocado and green leafy vegetables. According to Pryor (2000), vitamin E protects the 
body’s system against the production of malondialdehyde.  
 
Studies conducted by Orlich et al. (2014) and Haddad and Tanzman (2003) have shown 
that vegetarians tend to consume more legumes, nuts and seeds, as these serve as main 
sources of protein in their diet. In the famous EPIC-Oxford study on vegetarian diet and 
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lifestyle, vegans were observed to have the highest intakes of dietary vitamin E, 
compared with lacto-ovo vegetarians and non-vegetarians, probably indicating that the 
stricter the vegetarian diet, the higher the chance of obtaining high amounts of vitamin E 
(Davey et al., 2003 ). A study has even revealed that the level of vitamin E in the blood 
of lacto-vegetarians and lacto-ovo-vegetarians is comparatively higher than that of non-
vegetarians (Somannavar and Kodliwadmath, 2012). In this study, it was observed that 
the decreased level of vitamin A and E in the blood of non-vegetarians was associated 
with decreased levels of the enzymatic antioxidant glutathione peroxidase, as opposed to 
that of vegetarians who recorded comparatively high levels of both the enzymatic 
antioxidants and non-enzymatic antioxidant vitamins. 
 
2.9 Reactive Oxygen Species (ROS) and Oxidative Stress 
Reactive oxygen species (ROS) are chemically reactive molecules such as peroxides and 
oxygen ions (Glade, 2003) and are produced naturally, as by-products of the normal 
metabolism of oxygen (Virginie et al., 2012). They are generated and released during 
normal processes of body cells, such as the degradation of haemoglobin, as well as 
generated by the human immune system during the inflammatory response to injury by 
immune cells such as activated macrophages and neutrophils (Conforti et al., 2007). They 
are considered toxic to the body. Examples of ROS include hydroxyl radical, singlet 
oxygen, peroxyl radical, semiquinone radical and alkoxyl radical (Caballero, 2006). The 
mitochondria, cytochrome P450 metabolism, peroxisomes, and inflammatory cell 
activation are all endogenous sources of ROS (Inoue et al., 2003). 
 
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 According to Maxwell (1995), about 5%, or even more, of oxygen breathed in during 
inhalation is converted to ROS.  In the normal processes of cells, bonds that split usually 
result in molecules with paired electrons. However, in situations where weak bonds split, 
there is the formation of free radicals which are extremely unstable, and in a bid to gain 
some form of stability, react quickly with other compounds (Hamid et al., 2010). 
 
 According to Virginie et al., (2012), ROS is therefore a collective term for several 
oxidizing compounds such as hydrogen peroxides, superoxide anions, hydroxyl radicals 
that exhibit a characteristic high reactivity due to the presence of unpaired valence shell 
electrons. 
 
The formation of free radicals also occur in processes such as exposure to some 
environmental conditions, for example sunlight, radiation, high oxygen levels, microbial 
lysis during immune function, and oxidation of substrates with high affinity for oxygen, 
for example fatty acids (Caballero, 2006). Glade (2003) established that ROS can be both 
harmful and beneficial in biological systems depending on the environment. ROS benefit 
the body by taking part in the physiological roles of cellular responses such as cell 
signaling and defense against infectious agents (Glade 2003). However, at high 
concentrations, ROS causes “oxidative stress”, characterized by a result in damage to cell 
structures, including lipids and membranes, proteins and nucleic acids (Poli et al., 2004). 
Diseases such as degenerative diseases of aging, cancer, diabetes mellitus, protein energy 
malnutrition (PEM), cardiovascular diseases and atherosclerosis have been shown to 
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result from an overwhelming of the body’s system with ROS (Omoregie and Osagie, 
2011). 
 
A study confirmed that ROS levels increase drastically during conditions such as 
exposure to ultraviolet radiation and heat exposure (Devasagayam et al., 2004). ROS 
cause harmful results such as oxidation of polyunsaturated fatty acids (lipid peroxidation; 
whose product malondialdehyde is an indicator of oxidative stress), damage of DNA 
(leading to possible mutation), oxidation of amino acids in proteins and inactivation of 
specific enzymes by oxidation of co-factors (Brooker, 2011). Evidence from a study 
conducted by Turpeinen et al. (1998) therefore shows that oxidative stress could increase 
as a result of large intake of polyunsaturated fats, leading to endothelial malfunction. 
Also, a study by Vijayakumar et al. (2004) to determine the antioxidant effect of black 
pepper observed that rats that were fed a high fat diet exhibited significantly lowered 
levels of the antioxidant enzymes, glutathione peroxidase, superoxide dismutase and 
catalase as well as an increased level of thiobarbituric acid reactive species (TBARS) in 
the heart, aorta, liver and kidney. This further explains the relationship between ROS and 
diseases associated with very vital organs in the human body. Oxygen free radicals have 
been found to distort the structure and function of tissues, resulting in oxidative stress 
leading to so many diseases (Omoregie and Osagie, 2011; Kumar et al., 2012). 
 
Nutritional oxidative stress therefore is said to occur when there is a disturbance in the 
redox state caused as a result of either inadequate supply of nutrients that favour 
proxidant reactions or from excess oxidative load, resulting from excess free radical 
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formation and the inability of the antioxidant system to keep it under control (Sies et al., 
2005). 
 
 In another study that investigated the risk factors of ischaemic heart disease in rural 
populations of Nilgiris, south India, with focus on oxidative stress, researchers discovered 
that individuals with the disease had lowered levels of the antioxidants SOD, catalase and 
ascorbic acid in plasma, and an increased level of TBARS, which is a predictor of lipid 
peroxidation (Kumar et al., 2012). Conclusion was therefore drawn that the major causes 
of cardiovascular diseases amongst the rural populations of the Nilgiris, south India, were 
preventable causes such as smoking and high fat intake (thereby encouraging an 
increased rate of lipid peroxidation), all of which cause oxidative stress (Kumar et al., 
2012).  
 
A study on antioxidants, oxidant stress and essential fatty acids in vegetarians and non-
vegetarians revealed lower levels of plasma lipid peroxides in the former (Manjari et al., 
2001), suggesting that vegetarians have lower oxidative damage, compared with their 
non-vegetarian counterparts. A study carried out on the ability or otherwise of a 
vegetarian diet to provide genomic stability recorded significantly higher levels of DNA 
damage in the non-vegetarians compared with the vegetarians, although total antioxidant 
capacity between both groups were similar (Kazimírová et al., 2004). It was therefore 
concluded in the study that a vegetarian diet could provide some level of protection 
against oxidative stress. Results from a study by Somannavar and Kodliwadmath (2012) 
on the correlation between oxidative stress and anti-oxidant defense in South Indian 
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urban vegetarians and non-vegetarians revealed a significantly higher malondialdehyde 
(MDA) level in the non-vegetarian group, indicating increased lipid peroxidation in the 
non-vegetarian group, compared with the vegetarian group. These studies have proven 
that vegetarians are at a lowered risk on oxidative stress and damage. 
 
2.10  Diet and Antioxidant Levels 
Guidelines on how to get enough antioxidants through food include eating a rainbow of 
fruits and vegetables, choosing a colourful fruit and vegetable, choosing whole grain 
products, adding nuts to salad and soups and snacking on vegetables (Academy of 
Nutrition and Dietetics, 2009). In a study to determine oxidative DNA damage in relation 
to nutrition, it was concluded that an incorrect nutritional habit and lifestyle determines 
the extent of DNA damage in the body (Dusinská and Krajcovicová-Kudlácková, 2004). 
In this study, DNA strand breaks with apurinic/apyrimidinic sites, oxidized purines and 
oxidized pyrimidines were assessed and compared in 24 subjectively healthy vegetarians 
and 24 non-vegetarians. The results showed a significantly reduction in DNA strand 
breaks and oxidized purines in vegetarians. In the same study, a significantly higher 
intake of protective food commodities among the vegetarian subjects was observed.  
 
The antioxidant network is unable to function properly when intake of dietary 
antioxidants such as vitamins C and E, carotenoids, polyphenols and other micronutrients 
such as selenium is low or their availability to the body is impaired (Sies et al., 2005). 
When adequate dietary polyphenols are ingested, it helps lower the susceptibility of low 
density lipoproteins (LDL) to oxidation, and improves endothelial dysfunction (Sies et 
al., 2005).  
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Due to the fact that vegetarians consume many plant foods, such as cereals, pulses, fruits 
and vegetables, their diet contains more sources of antioxidant vitamins, such as vitamin 
C and E, than non-vegetarians, since they are likely to replace animal protein source with 
plant protein sources (Rauma et al., 2000). Levels of antioxidant trace elements like zinc, 
iron and copper have however been recorded as low in vegetarians as compared to non-
vegetarians, resulting from a higher intake of plant trace element absorption inhibitors, 
like phytates, found in most plants, in the former group (Krajčovičová-Kudláčková et al., 
2003). 
  
A study by Krajčovičová-Kudláčková et al. (2003) measured the levels of the antioxidant 
vitamins, vitamin C and vitamin E in vegetarians and non-vegetarians. Findings were 
that, an average plasma value of antioxidant vitamins, C and E as well as the ratios, 
vitamin C/vitamin E, vitamin E/ cholesterol (LDL protection), vitamin E/triacylglycerols 
(polyunsaturated fatty acid protection) were higher than the normal threshold  values in 
the vegetarian group. This indicates overthreshold plasma values of essential exogenous 
antioxidants in vegetarians, which means a reduction in the risk of occurrence of diseases 
caused by free radicals (Krajčovičová-Kudláčková et al., 2003).    
 
2.11  Antioxidant Protection 
Fortunately, oxidation caused by free radicals can be minimized by a range of 
antioxidants (Bjelakovic et al., 2007). The role of antioxidants in the body is to deactivate 
free radicals or slow down their action before they attack and cause damage to cells 
(Gupta and Sharma, 2006). Antioxidants are therefore the body’s first line of defense 
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against damage by free radicals. However, since ROS partake in certain important 
cellular activities and functions such as redox signaling, the duty of antioxidants is to 
keep the amount of ROS at a level that prevents destruction of the body’s cells and not to 
totally remove them (Rhee, 2006). Earlier studies into antioxidants involved the role of 
antioxidants in the prevention of rancidity in saturated fats, where the rate of oxygen 
consumption was monitored in a setup involving fat and oxygen in a closed container 
(German, 1999).  
 
The antioxidant protection system consists of endogenous antioxidants, dietary 
antioxidants and metal binding proteins (Percival, 1998). Dietary antioxidants include 
vitamin C, vitamin E, beta carotene and polyphenols, among others (Hamid et al., 2010).  
Examples of endogenous antioxidants include the enzymes copper/zinc and manganese-
dependent SOD, iron-dependent catalase (CAT), selenium-dependent glutathione 
peroxidase (GPx) as well as uric acid and bilirubin (Hamid et al., 2010).  This 
combination of protective ability is referred to as antioxidant capacity. Antioxidant 
capacity defines the ability of cells to protect themselves against oxidative stress through 
the different actions of the various intrinsic factors such as CAT, SOD, GPx and extrinsic 
factors obtained from foods such as vitamin A, C, E and phytochemicals (Kim et al., 
2012). The antioxidant enzymes carry out their catalytic activities effectively in the 
presence of trace minerals such as manganese, iron zinc, copper and selenium, which act 
as co-factors (Hamid et al., 2010). It is therefore possible that the ability of these 
antioxidant mechanisms to function properly may be affected and compromised through 
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inadequate dietary intake of the above mentioned trace elements (Duthie and Brown, 
1994). 
 
In humans, vitamin  E is a very powerful dietary antioxidant that exist as membrane 
bound in the cell and acts in its most active form, α-tocopherol (Hensley et al., 2004). 
The main function of vitamin E is to protect against lipid peroxidation and subsequent 
production of the harmful product, MDA, which is an indicator of oxidative stress (Pryor, 
2000). Oxidative damage is reduced by an overall improved antioxidant status above the 
threshold plasma values of the various essential antioxidants (Krajčovičová-Kudláčková 
et al., 2003).  
 
2.11.1 Superoxide Dismutase (SOD) 
Superoxide dismutase is an antioxidant enzyme considered as part of the first line 
antioxidant defence amongst others such as catalase (CAT), glutathione reductase (GSH), 
glutathione peroxidase and minerals, and works in accordance with them, performing its 
duty by quenching superoxide ions formed in the body (Gupta and Sharma, 2006). The 
co-factors of the superoxide dismutase enzymes are zinc, manganese and copper (Noori, 
2012). SOD catalyses the dismutation of the superoxide anion to an oxygen molecule 
(O2) and hydrogen peroxide (H2O2), which are less reactive species (Mates et al., 1999).  
 
A study carried out on transgenic mice showed the inability of the mice to survive for 
more than two weeks after birth, and a series of biochemical defects ascribed to oxidative 
stress, when SOD-2 (the superoxide dismutase gene) was knocked out. (Melov et al., 
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1999).This shows the significance of the presence of SOD in living systems. Diet has 
been found to affect the epigenetic regulation of the MnSOD gene (Thaler et al., 2009).  
 
Some studies have found that SOD concentrations are higher in vegetarians compared 
with non-vegetarians (Manjari et al., 2001, Rauma et al., 1995). Other studies however 
have found no significant difference in the SOD levels in vegetarians and non-vegetarians 
(Haldar et al., 2007), especially in situations where the individuals were suffering from 
chronic diseases like cancer (Kim et al., 2012). 
 
2.11.2 Catalase (CAT) 
Catalase plays its antioxidant role by reacting with hydrogen peroxide, produced from 
dismutation of the superoxide anion, to form H2O and O2, thereby, detoxifying hydrogen 
peroxide and protecting cells from any H2O2 produced within them (Mates et al., 1999). 
Catalase is an iron-dependent antioxidant (Hamid et al., 2010) and its activity is 
influenced by the amount of exogenous antioxidants consumed. For example, the activity 
of catalase was found to increase significantly when nephrotic rats were administered 
with soy protein and genistein (the major isoflavone of soybean) (Javanbakht et al., 
2014). Similarly, the activity of catalase has been found to be higher in workers 
chronically exposed to lead, after administration of beta carotene (Kasperczyk et al., 
2014).  
 
 
 
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33 
 
2.12  Fruits and Vegetables 
Antioxidants are found in a variety of foods such as vegetables, fruits, grains, cereals, 
eggs, meat, legumes, nuts and even tea (Rietveld and Wiseman, 2003). Research has 
shown that the risk of developing most types of cancers is doubled by low dietary intake 
of fruits and vegetables (Ames, 1994).  According to Amitom (2001), several health 
benefits such as prevention of age-related degenerative diseases, cancer and stroke, are 
associated with consumption of berries, due to the presence of certain phytochemicals. 
These phytochemicals when consumed enhance the production and activity of the 
endogenous antioxidant properties in the body (Amitom, 2001).  
 
Phenolic compounds which include phenolic acids, flavonoids and flavonolignans in 
certain herbs have been found to act as antioxidants at the molecular level (Craig, 1999) 
as well as help in the prevention of development of coronary artery disease (Hertog et al., 
1993). The study by Craig (1999) is supported with another study in which phenolic-rich 
plant extracts of Silybum marianum and Prunella vulgaris were administered to rats with 
high-sucrose diet induced oxidative stress. The results showed an overall increase in 
protective components against oxidative stress, including glutathione peroxidase and 
SOD (Škottová et al., 2003). All these related studies suggest that in a bid to increase 
one’s overall antioxidant status, a variety of plant foods is needed.  
 
2.13  Cereals and grains 
Other antioxidant compounds such as the polyphenolic antioxidants in foods, such as 
whole-wheat cereals are more stable (Baublis et al., 2000). Phenolic compounds or acids 
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34 
 
are present in all cereals and are derived from benzoic and cinnamic acids (Dykes and 
Rooney, 2007).The unique phytochemical composition of whole grains is part of the 
reasons why they are known to provide many health benefits. In a study that investigated 
the complete phytochemical profiles of free, soluble conjugated and insoluble bound 
forms as well as antioxidant activities in the uncooked whole grains, corn, rice, wheat and 
oats, corn was found to have the highest total phenolic content. Corn  recorded 15.55 ± 
0.60 μmol of gallic acid equiv/g of grain, followed by wheat, oats and rice, all of which 
recorded 7.99 ± 0.39, 6.53 ± 0.19 and 5.56 ± 0.17 μmol of gallic acid equiv/g of grain 
respectively (Adom and Liu, 2002). In the same study, the same trend was observed for 
grains that had the highest antioxidant activities. Corn had the highest antioxidant 
activity, followed by wheat, then oats and finally rice. Whole grain breakfast cereals have 
been found to have even higher antioxidant status than most fruits and vegetables, 
recording 2200-3500 trolox equivalents (TE)/100 g as compared to fruits and vegetables 
which recorded 600-1700 TE and 450 TE respectively (Miller et al., 2000). 
 
Studies have shown that due to the omission of animal protein from their diet, vegetarians 
consume more grain and cereal based diet compared to non-vegetarians and are therefore 
conferred all the benefits provided by this class of foods (Rauma et al., 2000 ; Orlich et 
al., 2014;  Haddad and Tanzman, 2003). 
 
2.14  Legumes, Seeds and Nuts 
Legumes are rich sources of folate, dietary fibre calcium, iron potassium, zinc and most 
importantly antioxidants. Nuts have been found to be among various dietary plants with 
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the highest content of total antioxidants and out of them, chestnut, walnuts and pecans 
have the highest content of antioxidants (Blomhoff et al., 2006). Consumption of 
legumes, precisely, soybeans have been inversely associated with the risk of type-two 
diabetes (Villegas et al., 2008).  It has been found that the best way to cook legumes and 
still preserve their antioxidant capability is through pressure boiling over a shortened 
processing time (Xu and Chang, 2008).  
 
Vegetarians have been found to consume more legumes, nuts and seeds, compared with 
non-vegetarians, since these food commodities serve as their main source of protein, as a 
result of omission of animal protein from their diet. (Rauma et al., 2000; Orlich et al., 
2014; Haddad and Tanzman, 2003). 
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CHAPTER THREE 
3.0 MATERIALS AND METHODS 
3.1 Study Design 
The research was a case-control study. The Purposive and convenience sampling 
techniques were used in recruiting participants for both the case and control groups.  
 
3.2 Study Sites 
The case group was recruited from the New Life Historic Seventh-Day Adventist church 
in Mayera, a suburb of Accra. The control group was obtained from a branch of the 
church in Dansoman. The congregation gathered together on Saturdays between the hours 
of 10:00 and 12:30 GMT for their religious fellowship.  
 
3.3 Subject Recruitment 
Prior to recruitment of participants, the nature of the study was explained to the 
authorities of the churches. The authorities then gave permission so that the rationale 
behind the study and the procedure of obtaining data was explained to the entire 
congregation. Ethical issues concerning the study were also clearly stated to the 
individuals and only vegetarian and non-vegetarian participants who willingly accepted 
to take part in the study were recruited. The subjects for the study were non-vegetarians 
between the ages of 18-50 and vegetarian adults, 18-50 years, who had lived a vegetarian 
lifestyle for not less than 2 years.  
 
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3.4 Sample Size Determination 
A sample size of 50 was determined based on the population of the Vegetarians’ 
Association of Ghana, Accra (about 300 members). An allowance of 10% and a non-
response rate of 20% were given. An absolute precision of 5% and a confidence interval 
of 95% were used in accordance with the strategic function of Epi Info Statistical 
Software were used. . 
 
   
          
  
  
   
                 
     
  
                                                            N=50 
Where ‘N’ is estimated sample size 
‘E’ is desired margin of error 
‘Z’ is the critical Z score on the desired level of confidence (95%)  
 ‘P’ is the prevalence of vegetarians in Accra.  
 
However, due to the difficulty in obtaining vegetarian participants, attributed to the small 
number of vegetarians in the Greater Accra Region, 39 cases and 30 controls were used 
in this study. 
 
 
 
 
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3.5 Subject Selection 
3.5.1 Inclusion Criteria: 
Participants included in the study were lacto-vegetarians, lacto-ovo vegetarians and 
vegans between the ages of 18-50 years. The control group made was made up of non-
vegetarian individuals. 
 
3.5.2 Exclusion criteria 
Individuals who had been vegetarians for less than twenty-four months, and vegetarian 
and non-vegetarian participants below the age of 18 years were excluded from the study. 
 
3.6 Ethical Approval 
Ethical approval for the study was obtained from the Ethics and Protocol Review 
Committee of the School of Biomedical and Allied Health Sciences (Ethical 
Identification Number: SAHS-ET./10396481/AA/10A/2013-2014. 
 
3.7 Pre-Testing of Questionnaire 
Questionnaire to be used for the study was pre-tested among a representative group of 
vegetarians in Sakumono, in the Greater Accra region, prior to the main study. Data 
obtained was reviewed and the questionnaire fine-tuned to suit the desired study 
population. Questions about dietary information such as intake of herbal preparations and 
the composition of the herbal preparations and frequency of consumption of fruits and 
vegetables were added. 
 
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3.8 Data Collection 
Collection of data was done in two phases. One phase involved the administration of the 
pre-tested questionnaires. Questionnaires were used to collect information which 
included socio-economic status, food frequency, previous medical history, demographic 
characteristics, anthropometry (height, weight and body mass index (BMI)) and other 
lifestyle risk factors (smoking and alcohol consumption). Blood pressure measurement 
was also taken from the participants. 
 
The second phase involved drawing of blood samples, by qualified laboratory scientists, 
from participants who had given their consent. 
 
3.9 Anthropometric Measurement 
Anthropometric data collected in the study included weight, height, body mass index 
(BMI), visceral fat and body fat. The BMI was obtained by dividing the weight (in 
kilograms) of each participant by the square of the height (in metres). All measurements 
were compared with various standards and normal ranges.  
 
3.9.1 Weight 
Weight was measured to the nearest 0.1 kg, using the BF= 506 Omron Healthcare Omron 
Body Composition Monitor (IL, USA). Participants were requested to empty pockets of 
all objects and remove shoes, socks and any extra clothing before standing on the scale 
for measurement to be taken. Participants were also requested to stand erect and still. 
 
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3.9.2 Height 
Height of participants was measured to the nearest 0.1 cm. The instrument used was a 
portable Seca stadiometer (Hamburg, Germany). Participants were requested to take off 
shoes and socks and stand on the base plate of the stadiometer, with their back and head 
straight. Their feet were placed together, with their heels touching the back of the plate of 
the stadiometer, and the head plate, lowered to touch the top of the head, noting the 
height of the participant. 
 
3.9.3 Visceral Fat and Body Fat Percentages 
Visceral fat and body fat percentages were also measured using the BF= 506 Omron 
Healthcare Omron Body Composition Monitor (IL, USA).  
The ranges for body fat and visceral were adapted from the Tanita Scale and were 
therefore classified as follows: 
 
Rating from 1 to 12 indicated healthy visceral fat 
Rating from 13-59% indicated excess level of visceral fat 
Body Fat: 
 
Figure 3.1 Body fat ranges for adults 
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3.10  Blood Pressure Measurement 
Blood pressure was measured in a calm environment. Subjects were made to sit upright, 
feet placed flat on a smooth ground and with the left arm relaxed on a hold-up, at a height 
approximate to the level of the heart. Participants were made to sit and rest for a 
minimum of 5 minutes before blood pressure was measured. The Omron HEM-742-E2 
(Hoofddorp, The Netherlands) was used to measure the blood pressure of the participants, 
two times at an interval of one minute, and the average taken as the blood pressure 
reading. 
 
3.11  Dietary Intake Assessment 
Food intake was assessed by obtaining dietary history of the participants through an 
interview. This was done using a 24 hour dietary recall (two week days and one weekend 
day), to assess current intake of food, and a validated food frequency questionnaire 
(Asare, 2011)  to assess usual food intake. Information on portion sizes of food consumed 
was also obtained and participants were assisted in estimating portion sizes, using food 
models. 
  
3.12  Blood Sample Collection and Handling 
Three millilitres of blood sample was drawn from the antecubital vein of participants into 
EDTA tubes. Blood samples were collected before 9:00 hours in the morning. Samples 
were kept in a cool box and transported to the Chemical Pathology Laboratory of the 
School of Biomedical and Allied Health Sciences, University of Ghana, Korle-bu 
campus. 
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3.13  Sample Preparation and Storage 
 Prior to storage, the blood samples were divided into two parts, one part for analysis of 
SOD and the other for catalase. For SOD analysis, 500 µl of whole blood was centrifuged 
using Heal Force Neofuge 23R (Shanghai, China) at 3000rpm for 10 minutes. The 
supernatant was discarded and red blood cells washed four times with 3.0 mls of 0.9% 
saline solution, with the supernatant being discarded after each centrifuge. The rest of the 
original blood samples were centrifuged at 5000 rpm for 5 min and plasma aliquoted into 
sample collection tubes. Washed red blood cells samples were stored at 4oC to preserve 
the cells, while plasma samples were stored at -20oC. 
 
3.14  Biochemical Analysis 
3.14.1 Superoxide Dismutase (SOD) 
The role of SOD is to accelerate the dismutation of the toxic superoxide (-O2) radicals 
that are produced during oxidative energy processes to hydrogen peroxide and molecular 
oxygen. 
 
(-O2)2   + 2H
+               SOD      H2O2  + O2 
 
The method employs xanthine and the enzyme, xanthine oxidase (XOD) to generate -O2 
radicals that react with 2-(-4-Iodophenyl)-3-(4-nitrophenol)-5-phenyltetrazolium chloride 
(I.N.T) to form a red formazan dye. SOD activity is measured by the degree of inhibition 
of this reaction.  
 
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3.14.2 Reagents 
Randox Laboratories Ltd. SOD kit was used according to the manufacturer’s protocol. 
The kit consisted of the following: 
1. Buffer 
2. Mixed substrate 
3. Ransod diluents (0.01 M phosphate buffer, pH 7.0) 
4. Standard 
5. Xanthine Oxidase 
 
3.14.3 Preparation of Standards 
The lyophilized standard was reconstituted with 10 ml of redistilled water and serial 
dilutions prepared as follows:   
 
 Volume of standard solution Volume of sample diluent 
S6 Undiluted Standard - 
S5 5 ml of S6 5 ml 
S4 5 ml of S5 5  ml 
S3 5 ml of S4 5 ml 
S2 5 ml of S3 6 ml 
S1 ----------- 5 ml 
 
 
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3.14.4 Sample Preparation 
Two milliliters (2ml) of cold redistilled water was added to the previously washed cells 
mixed and left to stand at 4oC for 15 minutes. The lysate was then diluted with 2.4 ml 
phosphate buffer, to achieve a 200-fold dilution factor (df) with percentage inhibition 
between 30% and 60%. 
 
3.14.5 Assay Procedure 
The procedure was followed according to the manufacturer’s instruction. The reaction 
was carried out at 37oC and absorbance read against air blank at 505 nm. The initial 
absorbance was read after 30 seconds and final absorbance, read after 3 mins. 
 
Calculation: 
     
 
                            
 
Sample diluents rate (S1 rate) = rate of uninhibited reaction =100% 
 
Rates of all standard and diluted samples were converted into percentages of the sample 
diluent rate and subtracted from 100% to give the percentage inhibition. 
 
    
                
          
               
 
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A curve of percentage inhibition for each standard against Log10 standard concentration 
of SOD U/ml was plotted. Using the percentage inhibition of the sample from the 
equation, SOD concentration was obtained from the standard curve. 
SOD units/ml of whole blood = SOD units/ml from standard curve x 200 (df) 
 
SOD units/g haemoglobin was then calculated using the equation: 
 
            
                
                          
 
3.14.6 Catalase   
The role of catalase is to accelerate the dismutation of toxic hydrogen peroxide radicals 
that are produced during oxidative energy processes, to water (H2O) and molecular 
oxygen. 
 
2H2O2                                                                                                2H2O  +  O2 
 
3.14.7 Reagents 
The analysis was carried out using the following reagents 
Buffer 
Potassium dichromate (K2Cr2O7) 
Hydrogen peroxide solution 
Distilled water (H2O) 
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3.14.8 Preparation of Standards 
Using six different concentrations of H2O2 as shown below, a standard curve was 
obtained. 
Concentration  Absorbance  
0 0.311 
0.1 0.667 
0.2 0.881 
0.3 0.905 
0.4 0.917 
0.5 0.987 
 
3.14.9 Assay Procedure 
Into a clean test tube, 0.2 ml of H2O2 was aliquoted and 0.5 ml of the buffer was added. 
To this, 0.05 ml of the sample was added and the flask swirled gently. Potassium 
dichromate (0.2 ml) was then added and the test tube heated in a boiling bath for 10 
minutes to decompose the blue precipitation and produce a green solution. The solution 
was then transferred into cuvettes and the absorbance read at 570 nm in the 
spectrophotometer. Using the standard curve, the amount of H2O2 (units/ml) remaining in 
the solution, when the enzyme was stopped with the potassium dichromate was 
determined. 
 
3.15  Data Processing and Analysis 
Dietary data was analyzed using the nutritional analysis software ESHA-FPRO version 5. 
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Statistical analysis was done using Statistical Package for Social Scientists (SPSS) 
version 17.0. Results of endogenous antioxidant levels were computed as one-tail whilst 
all other results were computed as two-tail and statistical significance was considered at a 
P-Value of ≤ 0.05. The independent t-test was used to compare mean levels of 
antioxidants among case and the controls. Qualitative data were summarized as 
proportions and percentages, whilst quantitative (height, weight and ages) was 
summarized as mean, standard deviation and ranges. Pearson’s correlation was used to 
assess relationship between intake of dietary antioxidants and serum and plasma levels of 
endogenous antioxidants.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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CHAPTER FOUR 
4.0 RESULTS  
4.1 Socio- Demographic Characteristics of Participants. 
A total of 69 participants were sampled for this study. Out of the 69 participants, 56.5% 
were vegetarians and 42.3% were non-vegetarians. Lacto-vegetarians constituted the 
majority of vegetarians sampled for the study. The mean age of all participants was 
33.9±8.8 years with vegetarian participants recording a mean age of 36.1±8.2 years, and 
30.7±7.6 years for the non-vegetarian participants. A greater proportion of vegetarians 
(33.3%) had education up to both the basic and higher national diploma (HND) level.  
 
More than half of the participants were employed (vegetarians= 71.8% and non-
vegetarians=76.7%), with vegetarians constituting majority of participants who were 
employed (54.9%). In relation to the marital status of the individuals, a greater number of 
both vegetarians and non-vegetarians were married (Table 4.1). 
 
 
 
 
 
 
 
 
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Table 4.1 Socio-demographic characteristics of participants 
Variables                                             V             NV 
 (n=39)            (n=30) 
     Frequency %      Frequency  % 
Gender 
Male      23   59.0   15   50   
Female     16  41.0   15   50 
   
Marital Status 
Single      14  35.9  13   43.3  
Married     21  53.8  15   50  
Divorced       1    2.6    0     0 
Widowed       3    7.7    2     6.7 
  
Educational Background  
No formal education      6   15.4     3  10   
Basic Education    13   33.3   10  33.3         
HND      13   33.3  10  33.3   
Tertiary       7   18.0     7  23.4 
 
Employment Status 
Employed     28  71.8   23   76.7  
Unemployed       5  12.8     1     3.3  
Student       3    7.7                6   20 
Retired       3    7.7     0.0     0.0 
 
 
4.2 Vegetarianism 
4.2.1 Types and reasons for choice of vegetarianism 
Lacto-vegetarians constituted 89.7% of the total number of vegetarians sampled, whilst 
lacto-ovo vegetarians and vegans constituted 7.7% and 2.6% respectively.  
 
About 64.1% of vegetarians reported they became vegetarians because of religious 
reasons. Others reported they did so to support health (25.6%), whilst a few (2.6%) 
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reported they did so to protect the environment (Fig 4.1). About 69.2% of vegetarians 
reported they had been involved in the lifestyle for a period of between 2-10 years whilst 
10.3% had been vegetarians for a period of between 21-30 years (Fig 4.2). 
 
 
Figure 4.1 Reasons for becoming a vegetarian 
0 
5 
10 
15 
20 
25 
30 
To uphold 
religious 
principles 
To support 
health 
To promote 
reference 
for life 
To protect 
the 
environment 
Fr
e
q
u
en
cy
 (f
) 
Reasons for vegetarianism 
Chart Title 
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Figure 4.2 Years of vegetarianism 
 
4.3 Dietary Habits and Meal Patterns of Participants 
A high percentage of vegetarians (56.4%) stated that they consumed two meals a day 
whilst non-vegetarians who ate three meals a day constituted 40.0%. Frequency of 
number of meals consumed in a day was similar among both groups. Majority of 
vegetarians (53.9%) and non-vegetarians (70.0%) reported that they did not skip 
breakfast. About 51.3% of vegetarians and 66.7% of non-vegetarians reported intake of 
snacks in between meals. Fruits and vegetables constituted the main snack item 
consumed by majority of vegetarians (65.0%), whilst pastries were consumed by most 
non-vegetarians (45.0%) as snack (Table 4.2). 
 
 
0 
10 
20 
30 
40 
50 
60 
70 
2 to 10  11 to 20  21 to 30  
P
e
rc
e
n
ta
ge
 (%
) 
Years 
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Table 4.2 Dietary habits and meal patterns of vegetarians (V) and non-vegetarians 
(NV) 
Characteristic Vegetarians 
(V) 
(n=39) 
Non-vegetarians 
(NV) 
(n=30) 
 Frequency % Frequency % 
Number of main meals/day     
One  2 5.1 1 3.3 
Two  22 56.4 17 56.7 
Three 15 38.5 12 40.0 
Skip Breakfast     
Yes 18 46.1 9 30.0 
No  21 53.9 21 70.0 
Snacks in between meals     
Yes  20 51.3 20 66.7 
No  19 48.7 10 33.3 
Types of snacks     
Fruits and vegetables 13 65.0 4 20.0 
Soft drinks   3 15.0 7 35.0 
Pastries    4 20.0 9 45.0 
Frequency of fruit intake     
Daily  19 48.7 5 16.7 
Once a week  14 35.9 16 53.3 
Once a month   3   7.7 8 26.7 
Occasionally    3   7.7 1   3.3 
Never    0.0   0.0 0.0   0.0 
 
4.4 Lifestyle Behaviours 
There was significant difference (p=0.02) between the consumption of alcohol in 
vegetarians and non-vegetarians. Alcohol consumption was reported by less than three 
percent (2.6%) of vegetarians whilst 20.0% of non-vegetarians reported consumption of 
alcohol. The most frequently consumed alcoholic beverage among non-vegetarians was 
beer (10.0%). This was mostly consumed weekly. Smoking was however not common 
among individuals of both study groups and the difference between smokers was not 
significant (p=0.20) (Table 4.3). 
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Table 4.3 Lifestyle behaviour of participants Vegetarians (V) and non-vegetarians 
(NV) 
Characteristic Vegetarians 
(V) 
(n=39) 
Non-vegetarians 
(NV) 
(n=30) 
 Frequency % Frequency % 
Current smokers 1 2.6 3 15.0 
Alcohol drinkers 1 2.6 6 20.0 
Type of alcohol     
Wine 0 0.0 1 3.3 
Beer  0 0.0 3 10.0 
Spirits 0 0.0 2 6.7 
Brandy  1 2.6 0 0.0 
Frequency intake of 
alcohol 
    
Daily 0 0.0 1 3.3 
Once a week 0 0.0 3 10.0 
Once a month 0 0.0 2 6.7 
Occasionally 1 2.6 0 0.0 
Quantity of intake of 
alcohol 
    
½ medium glass wine 0 0.0 1 3.3 
1 mini Guinness/beer   0 0.0 3 10.0 
1 tot of spirits/whisky 1 2.6 2 6.7 
Other 0 0.0 0.0 0.0 
 
4.5 Anthropometric and Blood Pressure Parametres of Participants 
Table 4.4 shows there were significant differences in the visceral fat percentage and 
systolic blood pressure between vegetarians and non-vegetarians (p=0.039 and 0.049 
respectively). However, there were no significant differences in weight, height, BMI, 
body fat and diastolic blood pressure between of the vegetarians and non- vegetarians  
(all p’s >0.05).  
 
 
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Table 4.4 Comparison of anthropometric and blood pressure measurement between 
Vegetarians (V) and Non-vegetarians (NV) 
 
                                     Anthropometric and blood  pressure measurement (mean ± SD) 
Variable Vegetarians 
(n=39) 
Non-vegetarians 
(n=30) 
p-value 
Weight (kg) 69.19 ± 13.13 69.62 ± 11.21 0.444 
Height (m) 1.66±0.08 1.65 ± 0.07 0.359 
BMI (kg/m2 25.23 ± 4.63 25.37 ± 2.87 0.445 
Visceral fat (%) 7.95 ± 4.49 6.27 ± 2.66 0.039* 
Body fat (%) 26..88 ± 11.00 23.80 ± 8.66 0.109 
Systolic BP (mmHg) 127.29 ± 17.39 122.03 ± 5.02 0.049* 
Diastolic BP (mmHg) 79.74 ± 10.19 79.87 ± 3.92 0.475 
*Significant at p≤ 0.05 
 
4.6 Frequency of Food Consumption 
4.6.1 Animal protein and vegetable protein 
Majority of vegetarians (66.7%) consumed vegetable protein on daily basis (everyday), 
whilst consumption of vegetable protein by non-vegetarians (56.7%) was observed to be 
mostly on weekly basis (once a week). Their sources of vegetable protein included 
“agushie”, soybeans and peanuts, consumed in the form of soups and stews, as well as 
non-dairy creamers. Only 12.8% of vegetarians consumed milk on daily basis compared 
to 40.0% of non-vegetarians.  About thirty-six percent (35.9%) of vegetarians however 
consumed milk about 2-3x/week (Figure 4.3). 
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V=Vegetarians  NV=Non-vegetarians 
Figure 4.3 Comparison of intake of animal protein and vegetable protein in 
vegetarians and non-vegetarians 
 
4.6.2 Fruits, Vegetables, Fruit juices and Soft Drinks 
A greater proportion of vegetarians (58.9%) than non-vegetarians (33.3%) consumed 
vegetables on daily basis. Vegetarians reported higher daily consumption of fruits 
(56.4%) than did non-vegetarians (16.7%). Frequency of daily consumption of fruit juice 
was higher among vegetarians (35.9%) than non-vegetarians (26.6%). Frequency of 
consumption of soft drinks was low in both groups (Figure 4.4). 
 
0% 
10% 
20% 
30% 
40% 
50% 
60% 
70% 
80% 
90% 
100% 
V NV V NV V NV V NV 
vegetable 
protein 
animal 
protein 
milk fatty meat 
P
e
rc
e
n
ta
ge
 (%
) never 
occasionally 
monthly 
2-3x/week 
weekly 
daily 
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V=Vegetarians  NV=Non-vegetarians 
Figure 4.4 Comparison of intake of vegetables, fruits, fruit juices and soft 
drinks/sweets in vegetarians and non-vegetarians 
 
4.6.3 Tubers, Cereals and Grains 
Figure 4.5 shows that higher proportions of non-vegetarians (33.3% and 60.0%) had 
respectively higher weekly and daily consumption of tubers and plantain than did 
vegetarians (20.5% and 30.8%). On the other hand, vegetarians reported a higher daily 
consumption of cereals and grains (61.5%) than did non-vegetarians (50.0%). 
0% 
10% 
20% 
30% 
40% 
50% 
60% 
70% 
80% 
90% 
100% 
V NV V NV V NV V NV 
vegetables fruit juices fruits soft 
drinks/sweets 
P
e
rc
e
n
ta
ge
 (%
) never 
occasionally 
monthly 
2-3x/week 
weekly 
daily 
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V=Vegetarians  NV=Non-vegetarians 
Figure 4.5 Comparison of intake of tubers, cereals and grains 
 
4.6.4 Fast foods, deep fried foods and pastries 
A greater proportion of vegetarians reported never consuming deep fried foods (33.3%) 
whilst 28.2% occasionally consumed deep fried foods. On the other hand, 6.7% of non-
vegetarians consumed deep fried foods weekly. The highest proportion of non-
vegetarians (40.0%) consumed deep fried foods occasionally. Vegetarians who never 
consumed fast foods (46.2%) were more than non-vegetarians (6.7%) who also reported 
never consuming fast foods. The proportion of vegetarians who never consumed pastries 
(30.8%) was greater than that of non-vegetarians (13.3%) who did not (Figure 4.6). 
 
0% 
10% 
20% 
30% 
40% 
50% 
60% 
70% 
80% 
90% 
100% 
V NV V NV 
tubers and plantain cereals and 
grains 
P
er
ce
n
ta
ge
 (%
) never 
occasionally 
monthly 
2-3x/week 
weekly 
daily 
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V=Vegetarians  NV=Non-vegetarians 
Figure 4.6 Comparison of intake of fast foods, pastries and deep fried foods 
 
4.7 Energy and Nutrient Intakes 
4.7.1 Macronutrient intake in vegetarians and non-vegetarians 
Total energy intake was not different between both groups. Protein intake was different 
between vegetarians and non-vegetarians, with vegetarian mean protein intake being 
lower than non-vegetarians (Table 4.5).  
  
 
 
 
0% 
10% 
20% 
30% 
40% 
50% 
60% 
70% 
80% 
90% 
100% 
V NV V NV V NV 
fast foods deep fried foods  pastries 
P
e
rc
e
n
ta
ge
 (%
) never 
occasionally 
monthly 
2-3x/week 
weekly 
daily 
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Table 4.5 Macronutrients intake in vegetarians (V) and non-vegetarians (V) 
 
Nutrient Vegetarians 
(V) 
n=39 
Non-vegetarians 
(NV) 
n=30 
p-value 
Energy/kcal 1871±243 1972±264 0.323 
Protein/g 
(% of energy intake) 
38.92±7.03 
(8.32%) 
62.99±14.87 
(12.78%) 
0.001* 
Carbohydrate/g 
(% of energy intake) 
288.82±60.86 
(61.75%) 
289.08±62.70 
(58.64%) 
0.212 
Fat/g 
(% of energy intake) 
57.26±15.60 
(27.54%) 
60.69±16.18 
(26.70%) 
0.554 
SFA/g 
 
8.8 ±4.9 12.6±6.4 0.003* 
MUFA/g 
 
8.3±4.1 9.4±4.6 0.27 
PUFA/g 
 
9.5 ±5.00 3.4±1.7 0.000* 
*Significant at p ≤0.05  
 
4.7.2 Mean daily intake of antioxidant vitamins and selected micronutrients  
There was a significant higher   intake of vitamin E in vegetarians than non-vegetarians 
(p=0.013). Vegetarians recorded the highest mean intake of vitamin C although the 
difference was statistically not significant (p=0.12). There was no significant difference 
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between the intakes of iron (p=0.41) and Vitamin A (p=0.16) between both groups. Low 
intakes of zinc among vegetarians were however observed (Table 4.6). 
 
Table 4.6 Micronutrients and dietary antioxidant intake in vegetarians (V) and non-
vegetarians (NV). 
 
Micronutrient 
 
Vegetarians 
(V) 
(n = 39) 
Non-vegetarians 
(NV) 
(n = 30) 
p-value 
Vitamin C/mg 80.46±61.38 61.99±24.06 0.12 
Vitamin E/mg 6.3±4.0 4.3±1.5 0.013* 
Vitamin A/ RE 1462±977 1187±457 0.16 
Iron/mg 20.6±12.6 22.8±6.58 0.41 
Zinc/mg 6.5±1.2 9.6±2.1 0.000* 
*Significant at p ≤0.05  
 
4.8 Biochemical Analysis 
Figure 4.7 shows that vegetarians in this study had significant higher mean levels 
(p=0.044) of serum superoxide dismutase (3437±1633 units/g haemoglobin) compared to 
non-vegetarians (2837±1106 units/g haemoglobin). There was no significant difference 
(p=0.075) between mean plasma levels of catalase in vegetarians and non-vegetarians 
(11.11±16.00 units/ml and 9.76±18.61 units/ml) respectively. However, vegetarians 
recorded comparatively higher mean levels of catalase (Figure 4.8). 
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Figure 4.7 Mean serum levels of superoxide dismutase in vegetarians and non-
vegetarians 
0 
500 
1000 
1500 
2000 
2500 
3000 
3500 
vegetarians non-vegetarians 
M
ea
n
 le
ve
l o
f 
SO
D
 (
u
n
it
s/
g 
h
ae
m
o
gl
o
b
in
) 
vegetarians 
non-vegetarians 
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Figure 4.8 Mean plasma levels of catalase in vegetarians and non-vegetarians 
 
Table 4.7 Correlation between intake of dietary antioxidants and serum (SOD) and 
plasma (catalase) enzymatic antioxidant levels 
 
 Superoxide Dismutase 
r-value           p-value 
     Catalase 
r-value           p-value 
Vegetarians 
N=39 
    
Vitamin A -0.22 0.17 -0.07 0.67 
Vitamin C 0.45 0.04* -0.06 0.72 
Vitamin E -0.29 0.08 0.46 0.03* 
Non-
Vegetarians 
N=30 
    
Vitamin A -0.07 0.72 -0.27 0.15 
Vitamin C -0.30 0.11 -0.22 0.25 
Vitamin E -0.11 0.55 0.02 0.90 
Significant at p ≤ 0.05 
9 
9.5 
10 
10.5 
11 
11.5 
veges non veges 
m
ea
n
 le
ve
l o
f 
se
ru
m
  c
at
al
as
e 
(u
n
it
s/
m
l)
  
veges 
non veges 
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Vitamin C showed a significant moderate positive relationship with superoxide dismutase 
in vegetarians (p=0.04), whilst Vitamin E also showed a moderate positive relationship 
with catalase, though that of vitamin E was not significant (p= 0.08). The observed 
relationship between vitamin E and catalase among the non-vegetarian group was 
however weak. In non-vegetarians, Vitamin C showed a negative relationship with 
catalase (Table 4.8). 
 
4.9 Relationship between years of vegetarianism and serum and plasma levels of 
endogenous antioxidants 
The number of years of vegetarianism correlated positively but weakly with superoxide 
dismutase. However, this relationship was significant (p=0.02). A weak negative 
correlation was observed between the years of vegetarianism and plasma catalase levels. 
(Table 4.9). 
 
Table 4.8 Correlation between years of vegetarianism and serum and plasma levels 
of endogenous antioxidants 
 
 
 
 
Superoxide dismutase 
r-value          p-value 
 
Catalase 
r-value          p-value 
 
 
 
0.372          0.02* 
 
-0.077          0.64 
Significant at p ≤0.05 
 
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CHAPTER FIVE 
5.0 DISCUSSION AND CONCLUSION 
5.1 Discussion 
This study was performed to help determine and compare the influence of diet on the 
serum and plasma antioxidant levels of vegetarians and non-vegetarians. The antioxidant 
enzymes Superoxide dismutase and catalase were chosen as the main antioxidants for the 
study. The increasing knowledge of the protective ability of antioxidants in the human 
body has resulted in extensive research work being carried out frequently.  
 
Studies on vegetarianism as well have become more frequent due to the ever growing 
population of people who as a result of personal, cultural or religious reasons decide to 
adopt vegetarianism. Earlier studies on vegetarians sought to determine the adequacy of 
the diet in meeting nutritional needs since the lifestyle was meant to omit certain foods 
that provide very indispensable macronutrient and micronutrients. 
 
Evidence that vegetarians tend to be older than non-vegetarians (Davey et al., 2003) 
supports the results from this study in which the mean age of vegetarians was 36.1±8.2 
whilst that of non-vegetarians was 30.7±7.6. Also, according to Davey et al. (2003), due 
to concerns about body size, weight and shape, more females than males opted for 
vegetarian and vegan diets. However, results from this study showed a reverse 
occurrence. More vegetarian males (59%) than female vegetarians (41%) were sampled 
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from the study, whilst an equal number of males and females were sampled in the non-
vegetarian group. This however could be due to sampling bias. 
 
Again, contrary to results by Davey et al. (2003) that showed vegetarians to be more 
educated than non-vegetarians, results of this study showed otherwise. Judging from the 
fact that about 64.1% chose to be vegetarians to uphold religious principles, this result is 
possible especially in a setting where not only knowledge, but to a large extent, religious 
doctrines influence the need to adopt vegetarian dietary lifestyle. Also, educational level 
of individuals could be dependent on their geological location. 
 
A Study on vegetarianism has reported fewer percentages of vegans, compared with 
lacto-vegetarians and lacto-ovo vegetarians (Toohey et al., 1998). This study was no 
exception. Results showed that vegans contributed the least percentage (2.6%) to the total 
vegetarian population. This shows that fewer vegetarians can adhere to a strict vegan diet. 
According to Smith et al. (2000), vegetarians are more likely to adhere to this lifestyle for 
a longer period than individuals who adapt weight-reducing diets. Long period of 
adherence to a vegetarian diet was observed in this study. About sixty-nine percent 
(69.2%) had been vegetarians for between 2-10 years whilst 10.3% had been vegetarians 
for between 20-30 years. 
 
Results from this study showed that participants were conscious of disease-causing and 
life threatening behaviours. This is evident in the small percentages of participants who 
smoked or consumed alcohol from both groups. Only few vegetarians smoked or 
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consumed alcohol. These results are supported by the EPIC cohort study, in which a 
conclusion was reached that certain lifestyle behaviours which included not smoking and 
moderate alcohol intake are the lifestyle behaviours of vegetarians (Key, 1999). 
 
No significant difference was observed in the BMI of the vegetarians and non-vegetarians 
in this study, although one study has recorded differences with non-vegetarians having a 
higher BMI than vegetarians (Appleby et al., 2002). Results however are in accordance 
with studies conducted by Kumar et al. (2012) (in rural Bangladesh), and Dourado et al. 
(2011).  
 
Vegetarian participants recorded a mean visceral fat percentage that was significantly 
higher than that of non-vegetarians. This could be attributed to the fact that the sample 
size in this study was very small. However, also considering the significant difference in 
the mean age between both groups and the fact that even intake of energy was not 
different between both groups, the evidence of increased visceral fat accumulation with 
increasing age, as well as decrease in the body’s metabolism with increasing age could 
account for the significantly high visceral fat percentage in the vegetarian group  
 
Another interesting observation was the result of no significant difference in the body fat 
percentage, though most studies have recorded a lower body fat percentage in vegetarians 
(Kumar et al., 2012, Turner-McGrievy et al., 2014, Delgado et al., 2000). However, 
results obtained are in accordance with that of Brathwaite et al., (2003). In that study, a 
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possibility of a reverse occurrence is seen when results of the study showed a significant 
association between a vegetarian diet and obesity.  
 
It is also known that diet is not the only factor that affects body fat deposition and 
distribution. Other factors that affect the body fat occurrence include genetics, old age, 
physical activity and gender. Older adults are known to deposit fat easily compared with 
younger adults. This could contribute to the result of the no significant difference in body 
fat since most vegetarians were older than non-vegetarians. Also, women tend to have 
more body fat deposition than men. 
 
The significant difference observed in the systolic blood pressure between both groups is 
in accordance with results from the Adventist Health Study-2 (AHS-2) on a study to 
determine the relationship between vegetarian diets and blood pressure which showed 
that vegan participants had lower systolic blood pressure than omnivorous participants 
(Key, 1999). 
 
Food intake by vegetarians and non-vegetarians differ in the source from which protein is 
obtained. However with the omission of animal protein, vegetarians need to incorporate 
more plant-based protein diet into their meals. Main sources of protein in a vegetarian 
diet are legumes, seeds and nuts. Results from this study showed that majority of 
vegetarians (66.7%) consumed vegetable protein more frequently than non-vegetarians 
(13.3%). As expected, not one vegetarian consumed any meat or animal flesh. This 
showed that vegetarian participants had an understanding of what the lifestyle was about.  
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Regular intake of processed meat has been shown to be associated with a high rate of 
deaths from cancer, of which free radicals play a role. This observation was seen more 
among the non-vegetarians who obviously consumed these products than the vegetarians 
(Khaw et al., 2008). 
 
 Nuts are great sources of dietary vitamin E in diet and have been found to be among 
various dietary plants with the highest content of total antioxidants. Of the nuts, chestnut, 
walnuts and pecans have the highest content of antioxidants (Blomhoff et al., 2006). 
Legumes are rich sources of dietary fibre, iron, potassium, zinc and most importantly 
antioxidants. Consumption of legumes, precisely, soybeans have been inversely 
associated with the risk of type two diabetes (Villegas et al., 2008).  It has been 
established that the best way to cook legumes and still preserve their antioxidant 
capability is through pressure boiling over a shortened processing time (Xu and Chang, 
2008).  
 
With reference to the food frequency questionnaire used in the study, the highest 
frequency for consumption of fruits (orange, pawpaw, pineapple, banana, apple, avocado) 
and vegetables (carrots, cabbage, tomatoes, okro and garden eggs) was found to be on 
daily basis (consumed daily) for vegetarian participants (59.0%), whilst that of non-
vegetarians was 33.3%.  Frequent consumption of local vegetables like cocoyam leaves 
(locally called “kontomire”), okro, turkey berries, garden eggs and tomatoes consumed in 
the form of soups or stews was recorded. Consumption of other exotic vegetables such as 
cabbage, carrots, green pepper, lettuce, cauliflower, was not a common practice observed 
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among this group. This may be due to fact that most of these vegetables are relatively 
expensive compared to local vegetables. Judging from the level of education of the 
majority, jobs available may not pay enough to grant them the benefit of consuming these 
expensive food commodities. For some however, consumption of these exotic vegetables 
may not be a common practice.  
 
Guidelines on how to get enough antioxidants through food include eating a rainbow of 
fruits and vegetables and choosing a colourful fruit and vegetables (Academy of Nutrition 
and Dietetics, 2009). Consumption of a wide variety of fruits and vegetables leads to 
adequate intake of iron, magnesium, potassium and copper (Waldmann et al., 2003). 
These micronutrients play important roles in the formation and efficiency in functions of 
superoxide dismutase (zinc, magnesium and copper dependent) and catalase (iron-
dependent) in the body. Also, frequent consumption of fruits and vegetables in 
vegetarians is very important because they are the main sources of vitamin C which is 
largely needed to facilitate the absorption of non-haeme iron in the body (Davey et al., 
2003). Adequate iron absorption is necessary because this micro nutrient serves as a co-
factor for the formation of the antioxidant catalase. 
 
From analysis of the data obtained in the study from the food frequency questionnaire, it 
was observed that the frequency of intake of cereals and grains such as rice, maize and 
wheat was higher among the vegetarian group (61.5%) than among the non-vegetarian 
group (50.0%). This is in accordance with a study conducted by Rauma and Mykkänen 
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(2000) in which more intakes of cereals and grains were recorded to be higher in 
vegetarians than in non-vegetarians.  
 
 Protective food commodities  including oil seeds, dark grain products and grain sprouts 
recorded in a study accounted for the maintenance in the integrity of the DNA strands, 
due to the role they play in the reduction of the action of reactive oxygen species 
(Dusinská and Krajcovicová-Kudlácková , 2004). When adequate dietary polyphenols, 
obtained from plant diets are ingested, it helps lower the susceptibility of Low Density 
lipoproteins (LDL) to oxidation, and improves endothelial dysfunction (Sies et al., 2005). 
 
Frequent consumption of fast foods and common deep fried foods such as “kelewele”, 
fried yam and fried sweet potatoes was not observed among both vegetarian and non-
vegetarian groups. However, vegetarians consumed less of these high trans-fatty acids 
containing foods frequently, compared to non-vegetarians. These results indicate that 
vegetarianism is viewed and understood as a health conscious lifestyle by the participants 
who practiced it, and this is evidenced by their record of having the lowest intake of fast 
foods and sweets, which are high in trans fat, saturated fat and refined sugars. This 
observation is supported by a study that recorded strong correlations and levels of 
agreement (p<0.001) between the ‘health conscious’ mentality and vegetarian dietary and 
lifestyle patterns in men and women (Northstone and Emmet, 2010). Frequent 
consumption of foods containing plant oils as well as their over-processing, results in 
high-fat intake, which could lead to an increased rate of lipid peroxidation (Kumar et al., 
2012). 
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Most studies conducted on the levels of endogenous antioxidants have found the levels of 
SOD and catalase to be higher in vegetarians than in non-vegetarians (Manjari et al., 
2001; Krajčovičová-Kudláčková et al., 1995). Results obtained from this study also 
showed a significant difference in the SOD levels between both groups. However, an 
insignificant difference was observed in the CAT levels between both groups. 
Superoxide dismutase is a zinc-dependent antioxidant. It has been established that 
inadequate intake of protein could affect the availability of zinc in the body and its ability 
to efficiently act as co-factor for SOD (Mohanty et al., 2002). However, it has as well 
been proven that high protein diet promotes increased homocysteine levels, which lead to 
exhibition of superoxide anions, and stimulation of the generation of ROS in cells 
(Gurujeyalakshmi et al., 2000). Production of superoxide anions means more scavenging 
task for SOD, thereby leading to a reduction of its levels in the body. On the other hand, a 
study has shown the activity of zinc-dependent SOD to be independent of the influence of 
dietary zinc and therefore deficiencies in the dietary component will not immediately 
reduce the activity of the enzyme (Aggett and Favier, 1993). It is possible therefore that 
the comparatively low levels of zinc in vegetarians did not affect the levels of SOD. On 
the other hand, the relatively higher intake of protein in the non-vegetarian group could 
account for the relatively low levels of plasma SOD in the non-vegetarian participants.  
 
Vitamin C has proven to be a very powerful antioxidant. The superoxide radical anion, 
hydroxyl radical, singlet oxygen and hydrogen peroxide are some ROS scavenged by 
vitamin C (Rose, 1989; Weber et al., 1996). Main sources of vitamin C are fruits and 
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vegetables. Although the result of the analysis of the current dietary vitamin C intake 
(from 24-hour recall) in this study did not show a significant difference between the 
vegetarian and non-vegetarian participants, vitamin C intake was higher in vegetarians.  
 
The result obtained from the food frequency questionnaire as well, showed a higher 
frequent consumption of vitamin C containing foods (fruits) among vegetarians. Plasma 
ascorbate levels are maintained through recycling, by certain mechanisms in the body. 
Although the processes involved are affected by the reducing environment that exists in 
metabolically active cells, this could imply that frequent and adequate dietary intake of 
vitamin C is also necessary to maintain the conservation of this essential nutrient, 
thereby, making it accessible for scavenging of ROS. 
 
Proper maintenance of plasma catalase level and activity, though iron-dependent, also to 
a large extent is dependent on SOD. A necessary synergistic relationship has been proven 
by an earlier study that showed the inhibition of catalase by superoxide radical (Kono and 
Fridovch, 1982). This therefore supports results of this study in which comparatively 
higher plasma SOD levels are associated with high catalase levels in vegetarians 
compared with non-vegetarians. This as well shows the importance of vitamin C in 
determining catalase levels, as this dietary antioxidant scavenges superoxide radical 
anion which has been shown to inhibit catalase. However, the difference in the plasma 
catalase levels between both groups was not significant. This could be attributed to the 
fact that vegetarian participants were older than non-vegetarians. Research has 
established that increase in age leads to a reduction in catalase levels (Sohal and Arnold 
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1990; Sullivan-Gunn and Lewandowski, 2013). In this study, mean age was significantly 
different between both groups (p=0.007), with vegetarians recording a higher mean age 
than the non-vegetarians. 
 
Results showed that vegetarians consumed significantly higher levels of polyunsaturated 
fatty acids (PUFA), compared to the non-vegetarian participants. Research has proven 
polyunsaturated fatty acids to be easily susceptible to lipid peroxidation (Brooker, 2011). 
However, research also has shown that the main role played by dietary vitamin E as a 
dietary antioxidant is to provide protection against oxidation of PUFAs (Percival, 1998; 
Pryor, 2000; Wolf, 2005). Comparatively higher dietary intake of vitamin E by 
vegetarians could therefore explain the maintenance of higher levels of plasma 
endogenous antioxidants due to a possible reduction in lipid peroxidation, compared to 
non-vegetarians. 
 
5.2 Limitations of the Study 
I. Due to the small sample size, findings may not be representative of the total 
vegetarian population in Ghana. 
 
II. The tool for nutrient analysis did not make provision for the assessment of intake 
of beta-carotene, which happens to be the main component of Vitamin A that 
plays a very large antioxidant role. 
 
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III. The dietary intake analysis tool also did not have some Ghanaian foods and 
products on the list and this made it difficult to effectively assess nutrient intake. 
On the other hand, some Ghanaian food commodities that were listed in the tool 
did not have values for some nutrient components like vitamin E, saturated fat, 
MUFA and PUFA, and so similar foreign alternatives were employed. 
 
IV. Possible underestimation or overestimation of dietary intake on the part of both 
groups of participants and researcher may have occurred due to the methods of 
dietary assessment. 
 
5.3 Conclusions 
Dietary vitamin C intake in vegetarians, showed a moderate positive correlation with 
SOD level. Other dietary antioxidants (Vitamins A and E) showed either a weak positive 
correlation or weak negative correlation with the levels of the enzymatic antioxidants, 
SOD and catalase. Significantly higher intake of dietary vitamin E was observed among 
participants in the vegetarian group.  This could account for the significantly higher mean 
level of superoxide dismutase in this group. Comparatively higher intakes of vitamins A 
and C in vegetarians, though not significant, could account for the higher levels of 
endogenous antioxidants in their blood.  
 
 Also, frequency of intake of fruits, vegetables, legumes, nuts and seeds, as well as 
cereals and grains were reportedly higher in vegetarians than in non-vegetarians, though 
not significantly different. With the exception of protein, of which vegetarians were 
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found to have significant lower intakes compared to non-vegetarians, macronutrient 
intake between both groups were found to be similar. Zinc intake was found to be higher 
in non-vegetarians. 
 
A similar study into antioxidant levels in vegetarians and non-vegetarians in Ghana could 
include assessment of serum levels of vitamins A, C and E, as well as take into 
consideration other factors like age, physical activity and disease conditions, which could 
positively or negatively affect antioxidant levels. 
There is the need to examine more enzymatic antioxidants as well as to quantify dietary 
antioxidants. 
 
 
 
 
 
 
 
 
 
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APPENDIX I 
INFORMATION SHEET 
I, Boadiwaa Ofori-Amanfo, am conducting a research on oxidative stress levels of vegetarians 
and non-vegetarians. I am a final year student offering MSc. Dietetics with the school of Allied 
Health Sciences, College of Health Sciences, University of Ghana, Korle Bu. 
 
The main focus of this proposed study is to determine the relationship between dietary intake and 
oxidative stress levels in vegetarians and non vegetarians. 
About 3ml of venous blood will be drawn from you. Body weight and height will be measured in 
upright position wearing light clothing and without foot wear using Seca weighing scale and a 
stadiometer respectively. The weighing scale will be sterilized with menthylated spirit after each 
use to prevent cross-contamination of participants. The researcher will sterilize her hand using a 
hand sanitizer after each section. You will answer a few questions about yourself. 
The information provided will not be harmful to you in any way. The participants will be assured 
of confidentiality by the researcher, that is, your data will only be known to the researcher and 
you, the participant, and the information will be kept under an encrypted sticks or password- 
protected computers. If the information is published in any scientific journal, you will not be 
identified by name. This study may contribute to the existing knowledge of vegetarian diet and 
oxidative stress levels. 
There is no risk involved in the study except little discomfort and bruises the participants might 
experience at the sight of the blood drawn. The laboratory technologists will be extra careful 
when drawing the blood sample to minimize bruises and/ or discomfort. In case the participants 
experience bruises or discomfort at the sight of blood drawn, first aid will be provided. 
University of Ghana http://ugspace.ug.edu.gh
101 
 
Participation in this study is voluntary, without any cost and you are free to withdraw at any 
point in time without losing any medical treatment. 
The researcher will be available and willing to answer any further questions about the research, 
now or during the course of the project. 
 
 
CONSENT FORM 
I agree that the research project named above has been explained to my satisfaction and I agree 
to take part in this study. I understand that I am agreeing by my signature/thumbprint on form to 
take part in this research project and I understand I will receive a signed copy of this consent 
form for my records. 
 
NAME OF RESEARCHER: ……………………………………………………………………… 
DATE: …………………………………… SIGNATURE: …………………………….............. 
TELEPHONE NUMBER: …………………………….. 
 
 
NAME OF PARTICIPANTS: ……………………………………………………………………. 
SIGNATURE/THUMBPRINT: ………………………. DATE: …………………………….. 
MOBILE NUMBER: ………………………………… 
 
 
 
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APPENDIX II 
QUESTIONNAIRE 
Participant’s ID ……………………….. 
Date………………………………………… 
Socio –Demographic Status 
Age of participant (years):  20-29 [     ] 30-39 [   ] 40-49[   ]  50 -59 [   ] 60 and above [   ] 
Gender :        Male [    ]                Female [     ] 
Marital Status:   Single [    ]             Married [     ]        Divorced [     ]           Widowed [     ]          
Separated [   ] 
Religion:         Christian [   ]       Muslim [     ]        Buddhists [     ] Hindu [    ]               others, 
please specify …………………………  
Educational Background:   No formal education [  ]     Basic education (middle/JHS) [  ] SHS/O –
Level [   ]     HND/Diploma Certificate [    ]   Bachelor Degree [    ]                Post Degree [    ] 
Employment Status:  Employed [   ]      Unemployed [   ]     Retired [   ]    Student [   ] 
a. Are you a vegetarian?       YES [    ]                  NO [    ]                                                  
 b .If yes, how long have you been a vegetarian?   ………………………………                
 c. Please indicate the type:   Vegans [    ]     Lacto-vegetarians [    ]                                 Ovo-
lacto vegetarian [    ]    Non vegetarian [   ] 
What is your main reason for becoming a vegetarian? 
To support personal health and healing [      ] 
To promote reverence for life [    ] 
To protect the environment. [     ] 
To uphold religious and philosophical principles. [    ] 
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B. LIFE STYLE BEHAVIOUR 
Do you smoke?   YES [    ]     NO [    ]                                                                                 
 a. If yes how often?    Daily [    ]   Weekly [       ] monthly    [        ] occasionally [     ] 
Do you drink alcohol?     YES   [     ]      NO [     ]                                                              
 If yes how often     Daily [    ]        Weekly [    ]     Monthly [     ]   Occasionally [    ] 
One serving of alcohol: 120 ml of wine (½ medium glass of dry wine) 
285 ml of beer (1/2 large beer bottle, one full mini Guinness) 
30 ml (1 tot) of spirit, whisky gin, akpeteshi and alcoholic bitters) 
60 ml of (brandy, vermouth, aperitif) 
          c. On average, how many servings of alcohol do you take daily? ............................. 
 
 
C.  ANTHROPOMETRIC AND PHYSICAL MEASUREMENTS 
15. Weight ………kg  16. Height……….meters 17. BMI……………….Kg/m2 
18. Body Fat………. % 19. Visceral Fat………% 20. Blood Pressure……… mm Hg  
 
 
 
 
 
 
 
 
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FOOD FREQUENCY QUESTIONNAIRE (Adapted from Asare J, 2011) 
Instruction: Please tick how often you consume any of the food items listed in the box 
FOOD GROUP Not often 1-2x 3-4x 5-6x Daily Never 
Starchy roots, plantain 
Cassava       
Plantain       
Cocoyam       
Yam       
Cereals and cereal products 
Maize       
Rice       
Bread       
Animal Products 
Fish       
Meat       
Poultry       
Eggs       
Milk       
Cheese       
Legumes, nuts and oil seeds  
Beans       
Groundnuts       
Bambara       
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Soybean       
Cowpea       
Melon seeds[Agushie]       
Fruits  
Orange       
Mango       
Pineapple       
Watermelon       
Banana       
Avocado Pear       
Vegetables  
Tomatoes       
Garden eggs       
Green leaves       
Okro       
Fats and oils  
Palm oil       
Refined oil eg coconut oil       
Margarine       
 
 
 
 
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   24-HR RECALL (CURRENT FOOD INTAKE) 
Time Meal Quantity 
 
Breakfast 
Weekend 1  
 
1. 
2. 
1. 
2. 
Weekday 1  
 
1. 
2.  
1.  
2.  
Weekday 2  
 
1.  
2.  
1.  
2.  
Mid-morning Snack   
 
Lunch 
Weekend 1  
 
1. 
2.  
1. 
2.  
Weekday 1  
 
1.  
2.  
1.  
2.  
Weekday 2  1.  
2.  
1.  
2.  
Mid-afternoon snack   
 
Supper 
Weekend 1  
 
1.  
2.  
1.  
2.  
Weekday 1  
 
1.  
2. 
1 
2.  
Weekday 2  
 
1.  
2.   
1.  
2.  
Late-evening snack   
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Catalase standard curve 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
y = 3.449x2 - 1.2644x - 0.9986 
R² = 0.9538 
-1.2 
-1 
-0.8 
-0.6 
-0.4 
-0.2 
0 
0 0.2 0.4 0.6 0.8 
Series1 
Log. (Series1) 
Poly. (Series1) 
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APPENDIX III 
 
 
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