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The Use of Dietary Supplements in 

Two Groups of New Zealand Children 

and Adolescents 

Jennifer Crowley 

A thesis submitted in partial fulfilment 

of the requirements for the degree of 

Master of Philosophy 

in Nutritional Science 

Massey University, Albany, New Zealand 

2001 



Dedicated to the memory 

of my parents, 

Betty and Jack Crowley 



Abstract 

In Western societies, personal responsibility for health has become an important pre­

occupation during the latter part of the 20th century, with guidelines issued by governments 

as part of encouraging a healthy lifestyle. Many sectors of any given society have embraced 

this issue, but often in different ways. Dietary supplementation, as part of general self­

medication, is particularly prevalent among women, but not exclusively so. Supplementation 

reflects concerns about dietary adequacy and an attempt to manage nutritional status. It may 

also be that by virtue of the roles which many women occupy, including as shopper and 

health care dispenser, they may be more exposed to dietary and health information that 

encourages a degree of dissatisfaction with existing diets and makes supplementation more 

attractive. The consumption of supplements by children suggests that supplementation 

reflects a range of group or social influences. Communication between family members and 

external sources of health information, for example, friends, the family doctor and the media, 

may also encourage the adoption and maintenance of supplementation patterns. 

The purpose of this study was to determine the use of dietary supplements in two different 

groups of New Zealand children and adolescents. The first group consisted of children 

between 1 and 14 years of age from rural and urban areas who were targeted for the pilot 

study for the Children's Nutrition Survey. The pilot study consisted of a pre-testing and 

validation component. In the pre-testing component, there were 428 children, 137 of whom 

were Maori, 147 were Pacific peoples and 148 European/Pakeha. In the validation 

component, there were 183 children, with 60 Maori, 63 Pacific and 60 European/Pakeha. 

Questionnaires were used to provide demographic data and information on food and dietary 

supplement use. The pilot study found that 12.8% of the children of 1 to 14 years of age 

consumed dietary supplements. Supplement use was highest in children in the age range of 1 

to 5 years (52.3%) and decreased to 47.6% in children 6 to 14 years. Maori and Pacific 

children were less likely to consume supplements than European/Pakeha children. The most 

popular supplements consumed were vitamin C, either alone or in combination with vitamins 

A and D, or echinacia (49.9%), and multi-vitamins (30.9%). Herbal combinations were 



consumed by 16.5% of the children. Most of the children who consumed supplements took 

them daily. 

Further study of the prevalence of dietary supplement use by children in New Zealand will 

take place in the proposed Children's National Nutrition Survey. 

The athletes' study provided the second set of data. One hundred year 9 and 10 children (67 

males and 23 females), who were identified as having potential in their respective sports, 

were recruited from two decile one North Shore secondary schools. Questionnaires were used 

to provide demographic data, information on the use of dietary supplements, influences on 

dietary supplement use and the perceived benefits of dietary supplement use. The mean age 

of the athletes was 13.5 years. Twenty-eight sports were represented. Seventy percent of the 

athletes took dietary supplements. Supplement use was higher in females (84.8%) than males 

(62.5%). Energy products, the most popular dietary supplement, were consumed by 43.1 % of 

the athletes. These were followed by vitamins (28.7%) and recovery products (7.1%). Meal 

replacers, herbal supplements and "other" (12.2%) were the least popular supplements. 

Vitamin C and multivitamins were the most popular vitamins consumed, while minerals were 

consumed only by a few athletes. Parents and coaches were found to be the most important 

sources of information amongst those who took dietary supplements (59.5%) and they were 

also found to be the most likely to be the person(s) who suggested taking dietary supplements 

(66.39%). Dietary supplements were perceived to benefit athletes' performances in a variety 

of ways, from providing more energy, to improving fitness, or to preventing illness. 

The findings from the athletes study suggests that sports organisations need to adopt a pro­

active stance to ensure that young athletes understand the importance of nutrition for both 

their sporting performance and their long-term health. 

11 



Acknowledgements 

There are a number people to whom I owe sincere thanks. Clare Wall who has supervised the 

thesis and done the job so willingly and extremely competently in spite of substantial 

commitments. I am grateful for her helpful comments. 

Viv McGuire has been involved with the preparation of the thesis and her skill in this area 

has been very valuable. My family have lived with the project as much as I have. Thank you 

to Paul who has been so supportive of my work and my sons Jacob and Nathan for their 

tolerance and understanding. 

There are others who have provided help, advice and information and in particular, I want to 

thank Patricia Kay and Sharon Bonham, Albany librarians at Massey University and Ingrid 

Radkey, reference librarian, University of Berkeley, California. 

lll 



Contents 
ABSTRACT 

ACKNOWLEDGEMENTS 

1 

2 

INTRODUCTION 

LITERATURE REVIEW 

2.1 DEFINITIONS AND REGULATIONS 

2.1.1 Vitamins: Nature, Classification and Functions 
2.1.2 Minerals: Nature, Classification and Functions 
2.1.3 Recommended Dietary Allowances 
2.1.4 The Regulation of Dietary Supplements 
2.1.5 Nutrition and Education Labelling Act, 1990 
2.1.6 Quality of Dietary Supplements 
2.1. 7 Non-Vitamins and Non-Minerals 

2.2 WHO NEEDS SUPPLEMENTS? 

2.2.1 Nutrition Experts 
2.2.2 Rational Combinations 
2.2.3 Supplementary Intake in Excess of the RDA 
2.2.4 Bioavailability 
2.2.5 Safety and Efficacy 
2.2. 6 Merging of Supplements and Medicines 

2.3 WHY Do PEOPLE TAKE SUPPLEMENTS? 

2.3.1 Key Players 
2.3.2 Demographic Factors and Lifestyles 
2.3.3 The Marketing of Supplements 

2.4 WHO TAKES SUPPLEMENTS? 

2.4.1 National Studies in the United States 
2.4.2 Other National Studies 
2.4.3 Non-Representative Studies 
2.4.4 Prevalence of Supplement Use 

2.5 WHAT Do PEOPLE TAKE? 

2.5.1 National and Non-Representative Studies in the United States 
2.5.2 Comparisons Between Countries 
2.5.3 Impact of Dietary Supplements 

2.6 CHILDREN'S STUDIES 

2.6.1 United States Children's Studies 
2.6.2 Other Children 's Studies 
2.6.3 What is Taken? 
2. 6.4 Impact of Dietary Supplements in Children 

2. 7 WHY SUPPLEMENTS ARE TAKEN? 

2. 7.1 Key Findings 
2.8 THE LIMITATIONS OF SUPPLEMENT USE 

2.8.1 Supplements: Health, Well-Being and Resistance to Disease 
2.8.2 Food: More Than the Sum of its Nutrients 
2.8.3 Intervention Supplement Studies 
2.8.4 Dietary Supplements: A Potential Source of Toxicity 
2.8.4.1 Fat-Soluble Vitamins 
2.8.4.2 Water-Soluble Vitamins 
2.8.5 Adverse Nutrient Interactions 

2.9 VITAMINS, MINERALS AND EXERCISE PERFORMANCE 

2.9.1 Impact of Vitamins and Minerals on Exercise Performance 
2.9.2 Supplements: Nutritional Aids to Exercise Performance and Health 

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2.9.3 Vitamin and Mineral Status of Athletes 
2. 9.4 The Relationship of Vitamin and Mineral Status to Performance 
2.9.5 Vitamins as Anti-Oxidants 
2.9.6 Sports Drinks and Electrolytes 
2.9.7 Trace Elements 
2.9.8 Effects of Exercise on Iron Status 
2.9.9 Why Athletes Use Supplements 

2.10 ADOLESCENTS 

2.10.1 Adolescent Athletes and Nutrition 
2.10.2 Adolescents and Supplements 

2.11 SUMMARY 

3 AIMS OF THE STUDY 

4 METHODS ONE: PILOT FOR THE CHILDREN'S NUTRITION SURVEY 

4.1 
4.2 
4.3 
4.4 
4.5 
4.6 
4.7 
4.8 

INTRODUCTION 

PILOT FOR THE CH1LDREN 'S NUTRITION SURVEY 

GOALS OF THE PILOT STUDY 

SAMPLE 

VALIDATION 

SAMPLE 

PRE-TEsTING 

STATISTICAL ANALYSIS 

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5 RESULTS: PILOT STUDY FOR THE CHILDREN'S NATIONAL NUTRITION SURVEY ......... 53 

5.1 
5.2 
5.3 
5.4 
5.5 
5.6 
5.7 
5.8 
5.9 
5.10 
5.11 
5.12 

INTRODUCTION 

WHO TOOK SUPPLEMENTS? 

SUPPLEMENTS BY AGE 

SUPPLEMENTS BY GENDER 

SUPPLEMENTS BY ETHNICITY 

WHAT WAS CONSUMED? 

FREQUENCY OF INTAKE 

M ATCHED CONTROLS 

VITAMIN C INTAKES 

SOCIO-ECONOMIC STATUS 

RECOMMENDED DIETARY INTAKE 

CONTROLS 

6 DISCUSSION: PILOT FOR THE CHILDREN'S NUTRITION SURVEY 

6.1 
6.2 
6.3 
6.4 
6.5 

INTRODUCTION 

RESULTS 

Soc10-EcoNOMIC STATUS 

WHAT WAS CONSUMED? 

IMPACT OF SUPPLEMENTS ON NUTRIENT INTAKE 

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7 METHODS TWO: SURVEY OF ELITE ATHLETES AND SUPPLEMENT USE ...................... 77 

7.1 
7.2 
7.3 
7.4 

SUBJECTS 

QUESTIONNAIRE 

STATISTICAL ANALYSIS 

ETHICAL APPROVAL 

8 RESULTS: ELITE ATHLETES AND SUPPLEMENT USE 

8.1 
8.2 
8.3 
8.4 

PROFILE OF THE ATHLETES 

SPORTS PLA YEO 

DURATION OF SPORTS PLA YEO BY ATHLETES 

DIETARY SUPPLEMENTS 

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8.5 
8.6 
8.7 
8.8 
8.9 
8.10 
8.11 
8.12 
8.13 

MULTIPLE USE OF DIETARY SUPPLEMENTS 

VITAMIN AND MINERAL INTAKE 

FREQUENCY OF INTAKE OF DIETARY SUPPLEMENTS 

FREQUENCY OF INTAKE OF VITAMINS AND MINERALS 

DURATION OF DIETARY SUPPLEMENT INTAKE 

DURATION OF VITAMIN AND MINERAL INTAKE 

SOURCE OF INFORMATION IN TAKING SUPPLEMENTS 

WHO SUGGESTED TAKING SUPPLEMENTS? 

How DIETARY SUPPLEMENTS HELP PERFORMANCE 

9 DISCUSSION 

9.1 
9.2 
9.3 
9.4 
9.5 
9.6 
9.7 
9.8 
9.9 
9.10 
9.11 

INTRODUCTION 

SUPPLEMENTATION PRACTICES OF ATHLETES 

USE OF DIETARY SUPPLEMENTS 

AGE 

GENDER 

SPORT 

TYPE AND AMOUNTS OF SUPPLEMENTS USED 

THE REASONS FOR DIETARY SUPPLEMENT USE 

SOURCE OF DIETARY SUPPLEMENT INFORMATION 

COMMENTS ON THE Two STUDIES 

SUGGESTIONS FOR FuRTHER RESEARCH 

10 CONCLUSION 

REFERENCES 

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Figures 

Figurel Groups That Influence Consumer Attitudes to Health ............ ... ... ........ 14 



Appendices 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

Literature Review Databases 

Development of Supplement Questions 

Dietary Supplement Questions 

Nutrition Supplements 

Principals' Permissions 

Consent Form 

Supplements Survey 

Follow-Up Letter 

Supplement Update 

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How Dietary Supplements Help Performance ............................... 161 

Pilot Study Supplement Users ... ......... ................... 166 



List of Tables 

TABLE 1 Studies of Vitamin and Mineral Supplement Use in the United States in Adults .. ............ ........ 19 

TABLE2 Characteristics of The Children Who Took Supplements ....... ............... 54 

TABLE3 Distribution of Supplement Intake ...................... 55 

TABLE4 Range of Supplements Taken by Children .... .................. 57 

TABLES Median and Range of Selected Micro-Nutrient Intakes for Children, 1-3 Years .... ................ .. 58 

TABLE 6 Median and Range of Selected Micro-Nutrient Intakes for Children, 4-7 Years ...................... 59 

TABLE 7 Median and Range of Selected Micro-Nutrient Intakes for Boys, 8-11 Years ...................... 60 

TABLE 8 Median and Range of Selected Micro-Nutrient Intakes for Girls, 8-11 Years ...................... 61 

TABLE 9 Median and Range of Selected Micro-Nutrient Intakes for Boys, 12-15 Years ...................... 62 

TABLE 10 Range of Selected Micro-Nutrients Intake for Girls, 12-15 Years ...................... 63 

TABLE 11 Vitamin C Quartiles for Food Only and Control Children, 1-5 Years ..... .......... ....... 63 

TABLE 12 Vitamin C Quartiles for Food Plus Supplement and Control Children, 6-14 Years .... ............ ... . 64 

TABLE 13 Children's Energy Intake and the Role of Supplements in Achieving the ROI 
for Fat-Soluble Vitamins 

TABLE 14a Subjects Who Achieved the RDI for Vitamins Bl, B2 and B3 With and 
Without Supplements 

TABLE 14b Subjects Who Achieved the RDI for Vitamins B6, Folate and B12 With 
and Without Supplements 

... ............ .... ... 65 

....... .......... ..... 66 

...................... 67 

TABLE lSa Subjects Who Achieved the RDI for Vitamin C With and Without Supplements ...................... 68 

TABLE lSb Subjects Who Achieved the RDI for Selected Minerals With and Without Supplements ...... ...... 69 

TABLE 16 Control Energy Intake and Percentage Who Achieved the RDI for Vitamins A, C and E .......... 70 

TABLE 17 The Percentage Who Achieved the RDI for Control B Group Vitamins .............. ........ 71 

TABLE 18 The Percentage Who Achieved RDI for Controls for Selected Minerals ............. ... ...... 72 

TABLE 19 Age, Sex and Ethnicity of Athletes ..... ................. 79 

TABLE 20 Sports Played by Athletes ... ................... 80 

TABLE 21 Duration of Sports Played by Athletes .. ..... ............... 81 

TABLE 22 Dietary Supplements Taken By Athletes ...................... 82 



TABLE 23 Details of Vitamin and Mineral Supplements Taken 

TABLE 24 Frequency of Intake of Dietary Supplements 

TABLE 25 Frequency of Intake of Vitamins and Minerals 

TABLE 26 Duration of Dietary Supplement Intake 

TABLE 27 Duration of Vitamin and Mineral Intake 

TABLE 28 Source of Information for Taking Supplements 

TABLE 29 Who Suggested Taking Supplements? 

TABLE 30 How Dietary Supplements Help Performances 

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NZ Herald 19 July 2000 



1 Introduction 

Since the late seventies, there has been an increased emphasis on preventative medicine and 

individual responsibility for health. This emphasis on personal responsibility has been 

accompanied by an increase in self-medication reflecting the public concerns about dietary 

adequacy. Approximately 40% of the population in the United States use vitamin and mineral 

supplements regularly, making them the major form of self-directed health-promoting 

behaviour practiced by the public (Ervin et al, 1999). Vitamin and mineral supplement use 

represents a self-conscious attempt on the part of users to manage their nutrition status 

through some knowledge and an awareness of the nutritional issues (Levy and Schucker, 

1987). As Western societies have become concerned with wellness, and more and more 

scientific studies establish a relationship between good health and good nutrition, the topic of 

supplementation assumes a new prominence (Shangraw, 1990). The market for supplements 

has burgeoned. By 1981, vitamin and mineral supplement sales in the United States totalled 

$1.7 billion (Kaplan et al, 1986). In 1988, they reached $2-2.5 billion (Shangraw, 1990) and 

by 1996, sales of vitamins and minerals and other food concentrates were valued at $4 billion 

a year (Thomas, 1996). 

Interest in the use of dietary or nutritional supplements appears to be growing in the United 

States in particular. It is not clear whether this interest is fuelled by recommendations from 

family, friends, the print and television media, advertising, health professionals or scientific 

literature. Some of the reasons people give for taking supplements include: to improve 

nutrition, to make up for nutrients missing in the food supply, to decrease susceptibility to or 

severity of disease, or to increase energy or improve performance (Schultz, 1982; Sabal and 

Marquart, 1994b). Herbs and other dietary supplements are also taken as alternatives to 

conventional medical therapies (Brody, 1995; Eliason et al, 1997; Ervin et al, 1999). Another 

factor that may contribute to increased interest in the use of supplements is scientific 

evidence linking diets high in some nutrients (vitamins A, C, and E, folate, beta carotene, and 

calcium) with a lower risk for diseases or other conditions including aging, certain cancers, 

heart disease, osteoporosis, or neural tube defects (Ervin et al, 1999). 

1 



The next sections review the literature on the debates that have emerged in recent decades, 

both scientific and non-scientific, and the empirical evidence concerning diet and 

supplementation. Much of the literature concerns the USA, primarily because of the sheer 

volume that has been generated in that country, but where there is material available for other 

countries, including New Zealand, that too is referenced and discussed. 

2 



2 Literature Review 

2.1 Definitions and Regulations 

2.1.1 Vitamins: Nature, Classification and Functions 

Vitamins are micro-nutrients. They are defined as a group of unrelated compounds that are 

needed in relatively small amounts in the body to perform highly specific metabolic, growth 

and maintenance functions (Keith, 1989). These compounds are widely recognised as 

necessary components in bodily processes, but they are also considered ancillary nutrients 

because they do not directly supply energy, serve as structural units for other compounds, or 

contribute substantially to body mass (Armstrong and Maresh, 1996). 

Vitamins are either classified as either fat-soluble or water-soluble. The fat-soluble vitamins, 

A, D, E, and K, are primarily stored in the liver but also in fat tissues, mainly subcutaneous, 

and can be accumulated at levels that are toxic. Water-soluble vitamins, vitamin C and B 

complex, are not appreciably stored in the body and must be supplied routinely in the diet. 

These vitamins are normally eliminated in the urine, because their plasma concentration 

exceeds the capacity for reabsorption by the kidneys (Armstrong and Maresh, 1996). It is no 

longer accepted that all water soluble vitamins are safe at any level and all fat soluble 

vitamins are toxic (Bendich, 1992). Vitamins perform numerous biological functions. 

Examples of these functions include the following: vitamin A is vital for epithelial cell 

function and maintenance of vision, growth processes and the body's immune response; beta­

carotene, the major precursor of vitamin A, plays a role as an anti-oxidant (Clarkson, 1991b); 

vitamin D possesses hormone-like activity promoting bone calcification and intestinal 

calcium absorption (Norman and Miller, 1984); vitamin E has important anti-oxidant 

functions protecting cell membranes from free radical damage (Kagan et al, 1989); vitamin K 

is involved in the formation of blood clotting proteins and osteocalcin, important for bone 

health (Suttie, 1984); and water-soluble vitamins serve as enzymes and coenzymes for lipid, 

carbohydrate, and protein metabolism (Chaney, 1982). Vitamins thus have diverse roles in 

the body, as do minerals. 

3 



2.1.2 Minerals: Nature, Classification and Functions 

Minerals are essential components of cell membranes, enzymes, and glandular secretions; 

they regulate osmotic pressure, acid-base balance, blood volume, and the activities of nerves 

and muscle. Minerals include the electrolytes sodium, potassium, chloride, calcium and 

magnesium (Armstrong and Maresh, 1996). The maintenance of relatively narrow limits for 

the concentrations of electrolytes, both inside and outside the cell, is required for nervous 

transmission and contractions to occur (Pivamik, 1989). The sensitivity of the heart muscle to 

electrolyte imbalances can lead to arrhythmias and possibly death (Armstrong and Maresh, 

1996). 

There are fifteen essential trace elements in the body; iron, zinc, iodine, copper, manganese, 

cobalt, selenium, molybdenum, arsenic, chromium, fluoride, lead, nickel, vanadium, and 

silicon and these metal ions are required in very small amounts such as micrograms or 

nanograms per gram, for optimal body function (Keen and Hackman, 1984). They have 

functions that are necessary in metabolism: they are components of body fluids, co-factors in 

enzymatic reactions, structural components of non-enzymatic macromolecules, or are vital 

for transport and release of oxygen and deficiencies could affect physical performance (Keen 

and Hackman, 1984). 

2.1.3 Recommended Dietary Allowances 

The Recommended Dietary Allowances (RDA) are defined as the levels of intake of essential 

nutrients that, on the basis of scientific knowledge, are judged to be adequate to meet the 

nutritional needs of most healthy persons according to the Food and Nutrition Board (FNB, 

1989). These may also be referred to as recommended dietary intake (RDI) and estimated 

average requirement (EAR). The RDA values are intended to ensure that most of the 

population (95%) would avoid the consequences of deficiency if the RDA in question were 

ingested daily according to the Council on Scientific Affairs (CSA, 1987). Nutrient intakes 

below the RDA do not necessarily indicate inadequate intake, but intakes below 75% of the 

RDA are a cause for concern in terms of an adequate supply of nutrients (Block et al , 1988). 

The RDAs do not cover the particular needs of nutrients by people with specific clinical 

4 



problems, nor is the research base as broad as the experts would choose with insufficient 

studies available to determine minimum and average nutrient requirements for each age and 

sex groups, or to estimate population variability in need, and to feel comfortable about the 

judgements made to derive the nutrient allowances (Thomas, 1996). The RDAs are therefore 

estimates of need, based on the data available (Lachance, 1998a). For some nutrients, there 

are no RDA because of no, or insufficient data, upon which to base a decision. The 

nutritional requirements of these nutrients are expressed as estimated daily intake 

(ESSADDI), estimated by the Food and Nutrition Board (FNB, 1989). 

At present, there is an evolving public and scientific debate over whether some nutrients at 

intakes well above RDAs may provide benefits beyond their essential function, that is the 

prevention of degenerative disease, as the RDAs do not recognize the prevention of non­

deficiency related degenerative disease pathology and the synergy between nutrients and 

non-nutrients for promoting optimum health (Lachance, 1998a). In 1986, the FNB 

acknowledged that the RDAs should include the prevention of disease and upper safety limits 

(Lachance, 1998a). The new figures for vitamins C, E and selenium released in 2000 include 

both a RDA and an upper limit which represents food and supplements for vitamin C and 

selenium intake and supplements alone for vitamin E intake (Nutrition Today, 2000). The 

optimum intake of any nutrient will probably vary substantially among individuals, 

throughout their life and in relation to specific needs (Thomas, 1996). 

Breskin et al (1985) suggest that the RDAs for children has generally been interpolated from 

information obtained from infants and adults and may be equated with amounts that will 

maintain a satisfactory rate of growth in specific age and sex categories, a view endorsed by 

the Canadian Paediatric Society (CPS), (1990). The amounts necessary to maintain maximum 

body stores are not always considered and whether maximum stores should be equated with 

optimum stores is unknown (Breskin et al, 1985). 

2.1.4 The Regulation of Dietary Supplements 

In the United States, supplement regulations are governed by the Dietary Supplement and 

Health Education Act 1994 (DSHEA). Dietary supplements are defined in DSHEA as 

5 



products intended to supplement the diet that bears, or contains, one or more of the following 

ingredients: (a) a vitamin; (b) a mineral; (c) an herb or other botanical; (d) an amino acid; (e) 

a dietary supplement used by man to supplement the diet by increasing the total dietary 

intake; or (f) a concentrate, metabolite, constituent, extract, or combination of any ingredient 

described in clause (a), (b), (c), (d), or (e). The law specifies that a dietary supplement is a 

product that is labelled a such and is not represented for use as a conventional food, or as the 

sole item of a meal, or the diet. These products can be ingested as a capsule, powder, gelcap, 

tablet, liquid, or other form. The DSHEA specifically excludes dietary supplements from 

regulations as food additives (Neisheim, 1998). 

The DSHEA basically applies the same conditions in defining the safety of dietary 

supplements as those used to define safety in foods: the supplements must be safe under the 

conditions recommended on the label or, if no conditions of use are suggested on the label, 

under ordinary conditions of use (Neisheim, 1998). The responsibility for safety is placed on 

the manufacturer of existing supplements, and the Federal Drug Authority (FDA) must 

establish unreasonable risk if the product is to be removed from the market for reasons of 

safety (Neisheim, 1998). 

2.1.5 Nutn"tion and Education Labelling Act, 1990 

In the United States, the 1990 Nutrition Education and Labelling Act (NLEA) allows health 

claims on foods and dietary supplements. Health claims are statements that characterise a 

relationship between a nutrient or food component and a disease or health-related condition 

(Neisheim, 1998). There have been five health claims approved for both food and dietary 

supplement labels since 1990. These claims relate to calcium and osteoporosis, folic acid and 

neural tube defects, fibre and whole oats and coronary heart disease, fibre from psyllium seed 

husk and coronary heart disease, and sugar alcohols and dental caries (Report of the 

Commission on Dietary Supplement Labels, 1997). The legal basis for the labelling claim is 

that (1) some substantiation exists, (2) the FDA should be notified within 30 days of its 

presence on the label, and (3) two additional sentences are added to such claims: "The 

statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, 

cure, or prevent any disease" (DSHEA, 1994). 

6 



Along with "structure function" claims, a retailer may provide literature on supplements 

which is supposed to be balanced scientifically and should not be misleading. Literature can 

be found in books and magazines as well as on the web sites of companies that sell 

supplements via the Internet. Literature limitations are contested by some members of the 

American supplement industry as threatening their absolute freedom of speech to provide 

whatever information they think appropriate, while other supplement industry groups 

demonstrate a growing boldness with their claims, even with mainstream dietary supplements 

(Thomas, 1996). While there may be some public health benefits from the promotion of 

supplements by increasing the public awareness of nutrients, diet, and the disease 

relationships, the risks might well outweigh the benefits: the promotional information fails to 

give information on food-related alternatives to supplements; the public rarely has the 

expertise to evaluate the information used in the promotion; consumer expectations of the 

product effectiveness may also be heightened by the hype and lead to the irrational use of the 

product (Thomas, 1996). 

2.1.6 Quality of Dietary Supplements 

In the United States, supplements fall into the grey area between food and drugs, and few 

federal manufacturing and formulation standards exist (Shangraw, 1990; Radimer et al, 

2000). Calcium from many commercial calcium products was found not to be bioavailable, 

and many of the principles of product quality, accepted as commonplace in the formulation 

and manufacture of pharmaceuticals, were rarely considered in the manufacture of vitamin 

and mineral products, such as potency, content, uniformity, disintegration, dissolution and 

stability (Shangraw, 1990). Some supplement labels now carry a statement that the product 

meets voluntary disintegration and dissolution standards developed by the US 

Pharmacopoeia, the scientific organisation that establishes drug standards, although expiry 

dates are decided on what is generally thought to be reasonable are not supported by stability 

experiments (Shangraw, 1990; Thomas, 1996). 

Patients with prescription drugs are monitored by their doctor or pharmacist and it quickly 

becomes obvious if a product is not producing the desired physiologic or therapeutic effect, 

but consumers taking non-prescription drugs monitor themselves in terms of how they feel 

7 



and this reinforces the need for, and adherence to, standards for vitamin and mineral 

supplements (Shangraw, 1990). 

In processing supplements, ingredients are both concentrated and distilled. This process 

involves heat, solvents and usually removes most of the compound from the raw material 

(Thomas, 1996). While there are those who believe that "natural" vitamins are better than 

synthetic ones because "natural" vitamins contain unidentified factors said to enhance 

nutrient utilisation, it is not known whether these factors exist, are present in the raw material 

or survive the extensive processing (Thomas, 1996). 

2.1. 7 Non- Vitamins and Non-Minerals 

The 1994 DSHEA broadened the traditional definition of dietary supplements which had 

previously only encompassed essential dietary nutrients. The terms used to classify non­

vitamins and non-minerals (NVNM) are confusing. For example, herbs are technically 

defined as "non woody seed producing plants that die at the end of the season" (Radimer, 

2000). Strict adherence to this definition would exclude many botanicals derived from trees, 

such as ginko and hawthorn. The term "herbal" in relation to dietary supplements is often 

used loosely and encompasses a variety of other botanicals as well (Radimer, 2000). 

Data on the prevalence and use of vitamins and minerals are readily available, but it is 

limited for NVNM. Sales data suggest that total intake of "herbs/botanicals" and "speciality 

products", for example, fish oils, shark cartilage, amino acids, is increasing with ginseng and 

garlic amongst the most popular (Radimer et al, 2000). The FDA conducted national 

telephone surveys in 1994 and 1995 and reported an 8% and 12% respective use of herbal 

supplements or teas (Roe et al, 1997). 

In NHANES III, while respondents were only asked about vitamin and mineral supplements, 

many reported other types as well. From this data, garlic and lecithin were found to be the 

most commonly used, and there was a suggestion that NVNM supplement use was associated 

with age and more healthful lifestyles, although there was also a link with higher alcohol 

consumption and obesity (Radimer et al, 2000). 

8 



2.2 Who Needs Supplements? 

2.2.1 Nutn'tion Experts 

Expert nutrition groups suggest that healthy children and adults should obtain adequate 

nutrient intakes from dietary sources and that meeting nutrient needs by choosing a variety of 

foods in moderation, rather than by supplementation, reduces the potential risk for both 

nutrient deficiencies and toxicities (see, for example, The Joint Public Information 

Committee of the American Institute of Nutrition and the American Society for Clinical 

Nutrition, 1987; CSA, 1987; ADA, 1996). Individual recommendations to take dietary 

supplements should be based on scientific evidence and come from doctors or dietitians after 

individual diet and nutrition assessment (The Joint Public Information Committee of the 

American Institute of Nutrition and the American Society for Clinical Nutrition, 1987; ADA, 

1996). 

There are instances when dietary supplements are advised, for example, where dietary 

selection is limited and for therapeutic nutrient supplementation. Nutrient supplementation to 

help meet the RDAs include: supplemental vitamin B12 for strict vegetarians who eliminate 

all animal products from the diet; folic acid for women of child-bearing age who consume 

limited amounts of fruits, leafy vegetables, and legumes; vitamin D for those with limited 

milk intake and sunlight exposure; calcium for those with lactose intolerance or allergies to 

dairy products; a multi-vitamin and mineral supplement for those following severely 

restricted weight-loss diets or the emotionally disturbed (CSA, 1987; Truswell, 1990; ADA, 

1996). Therapeutic supplementation is recommended in order to treat nutrient deficiency in a 

variety of specific clinical situations related to increased nutrient requirements, reduced 

nutrient consumption, absorption, or utilization, or increased nutrient excretion (CSA, 1987; 

Truswell, 1990; ADA, 1996). Also, as interaction between and among vitamins and drugs 

occurs, long term administration of some medications may place people at risk of vitamin 

deficiencies (CSA, 1987). 

Concerns about general nutrient intake, particularly of the more nutritionally vulnerable 

groups, has stimulated scientific discussion about whether to advocate the use of modest or 

9 



general doses of general multi-vitamin/mineral supplements to help meet RDAs (Keen et al, 

1994). In 1989, the FNB (1989) recommended that it was both practicable and desirable to 

meet the RDAs by consuming a variety of foods, and it was also the best way to ensure a 

balance of nutrients and the consumption of appropriate amounts of healthful food 

components for which there were no established RDA. While there is little scientific 

evidence of harm from the use of low-dose multi-vitamin/mineral supplements, it is possible 

that even modest amounts of vitamin and mineral supplements may contribute to excesses or 

imbalances (FNB, 1989; ADA, 1996) and therefore nutrient supplements should not be used 

as a substitute for healthful eating (ADA, 1996). 

2.2.2 Rational Combinations 

The dosage of therapeutic vitamins varies for different situations. Multiple vitamin 

preparations that claim effectiveness for the prevention or treatment of vitamin deficencies 

should be formulated on the basis of supplying all those vitamins whose combined 

deficiencies may be expected in a significant target population (CSA, 1987). The use of fat­

soluble vitamins alone is not recommended because the conditions that may lead to the 

depletion of some of these vitamins would be more rationally treated with all needed 

vitamins, except biotin and vitamin K as these deficiencies are rare (CSA, 1987). For water­

soluble vitamins, a preparation containing all B group vitamins, with or without vitamin C, to 

prevent or reverse disease is recommended for the following reasons: they are less well 

stored in the body than fat-soluble ones, they may be depleted more rapidly in the presence of 

an altered intake or disease, and several B group vitamins occur together in the same foods. 

(CSA, 1987). The vitamins should be combined in amounts from 50-150% of the RDA to 

prevent nutritional disease, and in amounts 2 to 10 times the RDA to treat disease (CSA, 

1987). 

2.2.3 Supplementary Intake in Excess of the RDA 

The National Research Council (NRC) recommends that individuals avoid taking 

supplements in excess of the RDA (NRC, 1989). In the 1987 National Health Interview 

10 



Survey, with the exception of vitamin C, most Americans, even those at the 90th or 95th 

percentiles of daily nutrient intake from supplements, received nutrient intakes which did not 

greatly exceed their RDAs (Subar and Block, 1990). However, a segment of the vitamin and 

mineral supplement user population consumed certain vitamins far in excess of the RDA: for 

10% of adult male and female users, the average daily intake of six vitamins, vitamins E, C, 

thiamin, riboflavin, vitamin B6, and vitamin B12 was greater than 15 times the RDA; for 5% 

of these men and women the average daily intake of thiamin, riboflavin, vitamin B6, and 

vitamin B12, was in excess of 30 times the RDA; and 5% percent of women consumed 

vitamin E at levels in excess of 35 times the RDA (Moss et al, 1989). At these levels, the risk 

of toxicity is greatly increased. Concern at the toxic intake levels of vitamin A among some 

women, based on NHANES III data, has also been expressed (Brech, 1999). 

2.2.4 Bioavailability 

A nutrient is bioavailable when it disintegrates and is dissolved in time for absorption in the 

body (CSA, 1987; Park et al, 1991). The bioavailability of nutrients contained in products 

depends on many factors, the type of mineral compound used, the physical form of the 

product (eg tablet versus gelatin capsule) , the substance used to coat the pill, and the 

thickness of the coating; the amount of pressure used to form the tablet; and other nutrients 

present that may interfere with the supplement nutrient (CSA, 1987; Park et al, 1991). It is 

recommended that all products marketed as single ingredients, or as combination products, 

should be in a form in which all active ingredients are biologically available, which has not 

always been the case (CSA, 1987). For example calcium, from calcium carbonate tablets, 

was not bioavailable; ferrous sulphate tablets have been recovered in patients stools and 

disintegration tests involving simulated gastric and intestinal juice demonstrated that some 

multi-vitamins took up to five hours to disintegrate (Shangraw, 1990). 

2.2.5 Safety and Efficacy 

Safety and efficacy are crucial but separate issues for vitamin and mineral supplementation. 

Efficacy is the ability of a supplement to provide a health benefit related to either prevention 

11 



or deficiency, or a reduction in risk of chronic disease, whereas safety is a reasonable 

certainty that there will be no adverse effects from excess intake of a nutrient (Hathcock, 

1993). Consumers probably consider both by assuming safety and judging efficacy in their 

individual decisions (Hathcock, 1993). While both issues are treated separately under federal 

labelling and safety regulations, they can also be treated in a manner that does not clearly 

separate them. For example, the safe and adequate daily intakes (ESADDI) of selected 

vitamins and minerals is used as an alternative to RDAs when the data are inadequate for 

setting a RDA (Hathcock, 1996). Another example is the term "safe and adequate" which has 

been misinterpreted as "safety limit" by the Codus Alimentarius Commission (Committee on 

Nutrition for Special Dietary Uses, Codex Alimentarius Commission, 1995). A more 

accurate definition of "safe and adequate" and the ESADDI would be "the recommended 

intake, an amount that is also safe" (Hathcock, 1996:p427). The RDAs are intended to be 

intakes that safely provide the known benefits for most healthy people (Hathcock, 1993). The 

margin of safety between the usual intake and the intake that would produce adverse effects 

varies greatly among different nutrients (The Joint Public Information Committee of the 

American Institute of Nutrition and American Society of Clinical Nutrition, 1987). High 

intakes of some nutrients have well documented adverse health effects that are variously 

described as toxicities, adverse reactions or poisonings (Hathcock, 1993). 

2.2.6 Merging of Supplements and Medicines 

The line dividing vitamins and minerals from drugs is, in many cases , gradually becoming 

less clear. Calcium supplements are used in the treatment of osteoporosis and are reported to 

be effective in treating some types of cancer and hypertension; iron is used in the treatment 

of iron deficiency anaemia; niacin has proved to be effective in lowering cholesterol levels 

(Shangraw, 1990). However, supplements that supply nutrients beyond what can reasonably 

be obtained from food should be viewed with caution and high potency products should not 

be used without thought and expert help (Thomas, 1996). 

12 



2.3 Why Do People Take Supplements? 

2.3.1 Key Players 

The proliferation of computer programmes and on-line services enhances the ability of 

consumers to self-manage their health and nutrition regimes but it also raises concerns about 

accuracy and the sources of information reaching consumers (McMahon, 1995; 1996). Those 

groups that seek to influence consumer attitudes and behaviours must realise and take · 

responsibility for the impact of their actions and the way in which they communicate via the 

media (McMahon, 1996). 

Examples of such groups include: the media, consumer product and the food service industry, 

regulatory and legislative bodies, scientific and academic communities, food nutrition 

education groups, professional organizations and consumer advocacy groups (McMahon, 

1995). There is interaction among and between these groups as seen in Figure 1. Consumers 

information comes from all these sources. The practice adopted by scientists, universities and 

professional societies of publishing the results of research by press release via the general 

media as a means of gaining publicity for their findings has a major flaw, as it typically fails 

to contextualise and explain complex findings in a way that is useful for consumers 

(McMahon, 1996). 

13 



Figure 1 Groups That Influence Consumer Attitudes to Health 

Science - Basic Research 

I \ 
Scientific Consensus 

Trade Policy Framework Consumer 
Organizations Consumer Message Development Activists 

Consumer Research/Focus Groups 

Message Refinement 
Scientific/Govt. Health Programs 

Media Health 
Educators Broadcast, Print and Electronic Professionals 

Consumers 

(McMahon, 1996) 

The majority of consumers in the 1995 American Dietetic Association (ADA) Nutrition 

Trends Survey agreed that new research findings should only be released after there has been 

general acceptance amongst nutrition and health professionals of their validity and that these 

findings needed to be put in a context that avoided confusion and misinformation (McMahon, 

1996). In spite of what is often a confused atmosphere of advertising and news reports of 

individual studies that show the benefits of supplements for numerous health issues, some 

consumers are still willing to make their own decisions about supplement use (Nesheim, 

1998). For example, media attention on the possible protective role of vitamins A, C, and 

beta-carotene against chronic diseases may be responsible for the increased intakes of these 

vitamins (Slesinski et al, 1995). 

14 



There is concern that the use of dietary supplements offers a false sense of security to some 

people who use them as a substitute for a good diet. It is natural for humans to want an easier 

way to achieve health without being vigilant, especially when short of time and feeling 

stressed. At such times, people may not exercise and food choices may be based on 

convenience and ease of preparation. When people avoid making lifestyle changes, taking 

supplements can become a deliberate, or unconscious, excuse for not trying to improve diet 

and lifestyles (Thomas, 1996). 

2.3.2 Demographic Factors and Lifestyles 

Changes in the demographics of consumers and their lifestyles have had a significant impact 

on how consumers accept nutrition and health information. The baby-boom generation, 

people born between 1946 and 1964, have driven many of the trends in the consumer 

marketplace throughout their lives (McMahon, 1998). They are very interested in living 

longer, and staying healthier for longer, than any other previous generation (Russell , 1997). 

Their interest in health and longevity has set the stage for the increased use of vitamin and 

mineral supplements, organic foods and for the introduction of functional foods and 

neutraceuticals (Messenger, 1997). 

2.3.3 The Marketing of Supplements 

The active marketing of vitamin and mineral supplements has contributed to their sales 

growth. In the past 20 years, there have been significant changes in the distribution of 

vitamin and mineral supplements in the United States. While they are still purchased from 

drugstores and health food stores, supermarket sales have increased through the growth of 

nutrition centres which provide, in addition to fresh foods, a broader line of vitamin and 

mineral supplements than previously available (Bender et al, 1992). This adds authority to 

their use. Dietary supplements are also available from mail order catalogues and small home­

based industries. All of these sales outlets attest to their widespread use and their growth into . 
a multi-million dollar industry (Eliason et al, 1997). Further, in the last 20 years, the 

emphasis of public health-related information on macro-nutrient disease relationships, while 

15 



still important, has been added to in the 1990s by a growing body of scientific literature 

supporting the importance of micro-nutrients to chronic disease relationships (Blumberg, 

1995). 

Arguments in support of taking regular vitamin supplements are often couched in terms of 

achieving "optimal nutrition". While not easily defined, an optimum diet may be considered 

to be one in which not only is disease prevented, but every system in the body is working 

with maximum efficiency (Basu and Dickerson, 1996). People who follow a healthy lifestyle 

often take supplements because of the media-promoted message that vitamin pills are part of 

a healthy life-style (Herbert, 1993). Both the medical profession and the public are often 

bombarded with "scare tactics" as well as genuine advertising (Spillman, 1996). 

2.4 Who Takes Supplements? 

2.4.1 National Studies in the United States 

Early studies in the United States on dietary supplements have focused primarily on the adult 

population, or groups within that population, and they tend to be limited in their 

comprehensiveness or representativeness. For example, there is limited data on the use of 

dietary supplements in children at a national level. Despite recommendations from the 

medical community that dietary supplements in adults or children are unnecessary, except for 

high risk groups, and that there is a lack of sufficient evidence which indicates beneficial 

effects, these studies generally indicate a high prevalence of use among adults and children 

(The Joint Public Information Committee of the American Institute of Nutrition and 

American Society for Clinical Nutrition, 1987; CSA, 1987; CPS, 1990). 

The National Health and Nutrition Examination Surveys (NHANES) are national, 

representative surveys of the United States population and constitute the most comprehensive 

research available. NHANES I was conducted between 1971 and 1975, NHANES II, 

between 1976 and 1980 and NHANES III, between 1988 and 1994. Supplement use was 

examined in these surveys according to a wide range of demographic data and behavioural 

characteristics. There were some overwhelming conclusions to the findings. For example, 

16 



NHANES I found that significantly fewer Black people than White consumed vitamins 

regularly (Block at al, 1988). Significant differences were also seen for age, sex, geographic 

region, education, poverty, type of alcoholic beverage consumed, and Quetelet index (Block 

et al, 1988). In the second survey, NHANES II, a higher nutrient intake and the use of 

vitamin supplements were particularly associated with older age, higher income, higher 

educational levels and being White. Of interest was the finding that people with higher 

nutrient intakes were still more likely to take vitamin supplements (Koplan et al, 1986). In 

NHANES III, approximately 40% of the American population took some form of 

supplements, and females were more likely to take supplements (44%) than males (35%). As 

with the previous survey, there was a trend for the increasing use of supplements with age, 

although children under five were an exception (see below), and supplement use was 

associated with high levels of education, income and self-reported health status (Ervin et al, 

1999). The higher incidence of supplement intake in the west of the United States among 

both men and women was also confirmed (Ervin et al, 1999). 

The other major national surveys are the National Health Interview Surveys (NHIS). These 

annual household surveys consist of a core set of questions, relatively unchanged each year, 

and one or more sets of supplementary questions (Kovar, 1985). Both the 1986 and 1987 

NHIS included questions on the use of vitamin and mineral supplements, and confirmed the 

demographic characteristics identified in the NHANES I, II and III studies (Koplan et al, 

1986; Block et al, 1988; Moss et a, 1989; Subar and Block, 1990; Ervin et al, 1999). In 1986, 

the rate of regular consumption was 36% in the two weeks prior to the interview (Moss et al, 

1989) and in 1987, 51 % of adults had consumed supplements in the previous year (Subar and 

Block, 1990). 

One national telephone survey reported that supplement use was more prevalent amongst 

women than men and above average consumption of supplements occurred in the western 

United States (Stewart et al, 1985). Another national telephone survey divided adult 

supplement users into four groups; Light, Moderate, Heavy, and Very Heavy, on the basis of 

the type and amount of nutrient intake from supplements (Levy and Schucker, 1987). Young 

supplement users (16 and 25 years) tended to be in the Light user group. Older adults (41 and 

64 years) and residents of the western United States tended to be in the Heavy and Very 

17 



Heavy user groups. Light and Moderate users tended to take a broad-spectrum supplement as 

insurance against possible nutrient deficiencies. Heavy and Very Heavy users typically took 

two or more specialised products as part of a personalised supplement regimen, and were 

associated with more frequent visits to health food stores, greater nutrition activity and less 

physical involvement (Levy and Schucker, 1987). 

2.4.2 Other National Studies 

In a representative sample of the Dutch population, it was reported that more than 17% 

consumed supplements (Dorant et al, 1993). Age, sex, social class, alternative food habits, 

smoking and adherence to a special diet were related to the use of supplements but not region 

of residence, in contrast to the United States research findings (Dorant et al, 1993; Ervin et al, 

1999). Adherence to special diets was also found in the United States and Australia (Horwath 

and Worsley, 1989; Kim et al, 1993). In Australia, women were more likely to be supplement 

users as in the United States (Worsley and Crawford, 1984a; Block et al, 1988). Supplement 

use increased with age in the Netherlands as it did in the United States, but no such 

association was found in Australia (Willet et al, 1981; Worsley and Crawford, 1984b; Kaplan 

et al, 1986; Block et al, 1988; Subar and Block, 1990; Dorant et al, 1993; Ervin et al, 1999). 

About half the New Zealand population (51 %) used vitamin and or mineral supplements 

during the year preceding the 1997 National Nutrition Survey (Russell et al, 1999). Women 

were more likely to take supplements than men and to take them regularly rather than 

occasionally. Regular use remained relatively constant across all age groups while occasional 

use declined with age. Provincial and metropolitan females reported similar supplement use 

while metropolitan males reported higher use than provincial males (Russell et al, 1999). 

2.4.3 Non-Representative Studies 

Non-representative studies are studies that usually only involve small numbers of subjects 

and the results relate to a particular region or area of the country rather than the entire nation. 

In the United States, non-representative studies that have investigated demographic data such 

as education, income and occupation have also found strong socio-economic influences on 

18 



supplement intake (Boatman and Wertheimer, 1980; Willet et al, 1981). One study found that 

the consumption rate among younger supplement users was significantly higher than in older 

supplement users (Schultz et al, 1982) while another study found that supplement use was not 

significantly related to educational achievement (Sowers and Wallace, 1986). These non­

representative studies support the findings of national surveys, that there was a greater 

prevalence of the use of supplements in the west of the United States where adults, especially 

women, had more concerns about their health (Willet et al, 1981; Schultz, 1982). Women's 

concerns about their health and supplement use were confirmed in an ADA survey (1997) 

where it was reported that a significant increase in consumers, especially women, believed it 

was necessary to take nutritional supplements in order to ensure proper health (McMahon 

1998). 

An Australian survey reported that 37% of men and 53% of women took some form of 

supplement and overall supplement use appeared to be unrelated to occupation and 

educational status (Worsley and Crawford, 1984a). This finding contrasts with another 

Australian study where it was found that significant differences in the intake of vitamins and 

minerals existed among different adult social status groups, in both foods and supplements in 

adults, and that women and high social status men were the main users of vitamin and 

mineral supplements (Smith and Baghurst, 1993). 

Table 1 

1971-1974 
1976-1980 
1980 
1986 
1987 
1987 
1988-1994 
1992 

Studies of Vitamin and Mineral Supplement Use in the United States in 
Adults 

32.9 NHANESI Block et al, 1988 
A rox 35 21.4 NHANESII Ko Ian et al, 1986 
39.9 FDA Stewart et al, 1985 
36 NHIS Moss et al, 1989 
51.15 23.1 NHIS Subar and Block, 1990 
22.5 NHEFS Kim et al, 1993 
A rox 40 NHANES III Ervin et al, 1999 
46.2 24 NHIS Slesinski et al, 1995 

19 



2.4.4 Prevalence of Supplement Use 

In the United States, the proportion of the population consuming supplements on a daily basis 

and the demographic pattern of usage has not changed significantly in the past two decades. 

In NHANES I, II, and III, differences exist in the manner in which supplement use was 

defined but the prevalence was similar throughout. In NHANES I and II, respondents chose 

between regular use (defined as daily consumption) irregular use (defined as at least once per 

week) or not taken. In NHANES III, consumption of any type of supplements in the month 

before the interview was recorded. In NHANES I, 32.9% of adults 18 to 74 years were 

regular, or irregular users, of whom 22.8% used supplements regularly (Block et al , 1988). In 

NHANES II, almost 35% of adults 18 to 74 years were regular or irregular users, of whom 

21.4% consumed supplements regularly (Koplan et al, 1986). In NHANES III, 42% of adults 

20 to 74 years used any type of supplement (Ervin et al , 1999). 

Other national surveys also report a fairly stable prevalence of use in the last two decades. 

For example, almost 40% of adults consumed vitamin and mineral supplements on a daily 

basis 14 days prior to interviews in a Food and Drug Administration (FDA) Survey (Stewart 

et al, 1985). In the 1986 NHIS, it was reported that 36.4% of adults and 43% of children used 

vitamin and mineral products (Moss et al, 1989). In the 1987 NHIS, a supplement use rate of 

38.7% was reported amongst adults when the reference period of Stewart et al (1985) was 

approximated (Subar and Block, 1990). A 4% decline in supplement use amongst adults was 

seen between the 1980 FDA survey (42%), and the 1986 NHIS (38%) (Bender et al , 1992). A 

similar decline in supplement use amongst adults between the 1987 (51 %) and 1992 (46%) 

NHIS was also reported (Slesinski et al, 1995). Direct comparisons across all of these 

surveys cannot be made, but the results suggest that the prevalence of supplement use among 

adults remained fairly stable over the past 20 years (Ervin et al, 1999). 

The magnitude of supplement use decreased in the 1980s but the prevalence of light users 

taking broad-spectrum products, usually people under 45 years, increased and supplement 

use, became more likely and more intense among individuals with one or more health 

problems and those who perceived their health as good (Bender et al, 1992). 

20 



The prevalence of dietary supplement use in the Netherlands at 17% was lower than that 

reported in the United States, or Australia (Worsley and Crawford, 1984; Kaplan et al, 1986; 

Block et al, 1988; Dorant et al, 1993). However, the mean number of different types of 

supplements used in the Netherlands for both sexes was 1.5, close to the 1.7 mean in the 

United States in 1992 (Bender et al, 1992; Dorant et al, 1993). 

In both the United States and the Netherlands, the prevalence of supplement use among 

heavy smokers was considerably less than that among non-smokers, or light smokers (Block 

et al, 1988; Subar and Block, 1990; Dorant et al, 1992). In NHANES II, former smokers were 

the heaviest supplement users, followed by non-smokers (Kaplan et al, 1986). In the 1987 

NHIS, supplement use was more common, in non-smokers, especially former smokers , and 

those who did not drink alcohol heavily (Subar and Block, 1990). 

2.5 What Do People Take? 

2.5.1 National and Non-Representative Studies in the United States 

In both national and non-representative studies in the United States, the most commonly 

consumed specific supplements in adults were multi-vitamins, vitamin C, vitamin A and 

calcium (Schultz, 1982; Sowers and Wallace, 1986; Block et al, 1988; Moss et al, 1989; 

Merkel et al, 1990). The use of specific preparations such as vitamins A, B group and C 

increased with age (Willet et al, 1981; Levy and Schucker, 1987; Moss et al , 1989; Ervin et 

al, 1999). Multi-vitamins alone, or in combination with iron, were consumed by similar 

proportions of men and women (Stewart et al, 1985; Moss et al, 1989). Vitamin C was 

consumed either alone, or in combination with other nutrients (Stewart et al, 1985; Moss et 

al, 1989; Park et al, 1991; Ervin et al, 1999). Calcium and iron were the most commonly 

included minerals in products (Moss et al, 1987; Park et al, 1991). 

While most adults consumed only one supplement, the number of adults who took more than 

one supplement varied between the studies (Stewart et al, 1985; Moss et al, 1989; Ervin et al, 

1999). Almost 11 % of adults had consumed five or more products in a national telephone 

survey (Stewart et al, 1985) and 5% of adults consumed at least five products in the 1987 

21 



NHIS (Moss et al, 1989). In the 1987 NHIS, the median intake from supplements was 100-

200% of the RDA for men women and children (Moss et al, 1989). Specialised vitamins 

such as vitamin A, C, and E were generally consumed in quantities many times the RDA in a 

survey among registered nurses (Willet et al, 1981). However, in the 1987 NHIS, it was 

noted that few if any supplements were consumed in amounts considered to be toxic (Subar 

and Block, 1990). 

2.5.2 Compan·sons Between Countries 

As in the United States, multi-vitamins and vitamin C were commonly consumed in both the 

Netherlands and Australia (Worsley and Crawford, 1984a; Dorant et al, 1993; Ervin et al, 

1999). Multi-vitamins and/or multi-mineral combinations were commonly consumed in New 

Zealand with vitamin C consumed by a relatively small proportion of the population (Russell 

et al, 1999). While vitamins A and D were consumed by adults in the United States, they did 

not rank among the most commonly consumed vitamins, as they did in the Netherlands 

(Dorant et al, 1993; Moss et al, 1989; Subar and Block, 1990). In the Netherlands, other 

supplements, especially garlic and brewer's yeast, were widely consumed amongst older 

adults (Dorant et al, 1993). In some studies in the United States, the use of other 

supplements, such as kelp and brewer's yeast, are prominent (Block et al , 1988; Schultz et al, 

1982). In NHANES I, only 2.3% of the total population reported use of supplements not 

categorised as vitamins or minerals (Block et al, 1988). However, the use of NVNM in the 

United States has slowly grown to 12% in NHANES III (Radimer et al, 2000). In contrast, 

Australia's first national survey in 1979 found that bran was the most frequently used dietary 

supplement (Worsley and Crawford, 1984a). In New Zealand, 29% of the population 

reported the use of other dietary supplements: the three most common categories of 

preparations taken were garlic, oils, such as evening primrose and botanicals (Russell et al , 

1999). 

22 



2.5.3 Impact of Dietary Supplements 

Several studies have investigated the impact of dietary supplements on nutritional status. 

Looker et al (1988) examined NHANES II data to compare dietary intake and biochemical 

indices of several nutrients and food groups in adult regular supplement users and non­

supplement users. Supplement users consumed more dietary vitamin C, and ate fruit and 

vegetables more frequently, than did non-supplement users. Also, iron status was reported 

not to be associated with supplement use (Looker et al, 1988). 

NHANES II data was analysed for both adults and children to evaluate the effect of the 

regular use of nutritional supplements on serum vitamin C levels (Dickinson et al, 1994) . 

Regular supplement use had a strong impact on serum vitamin C levels, independent of other 

dietary and demographic characteristics of supplement use that may have favoured improved 

nutritional status (Dickinson et al, 1994). 

The relationship between the reported use of vitamin and mineral supplements and mortality 

in a national cohort of adults was analysed from the NHANES I Epidemiologic Follow-up 

Study (NHEFS) and no evidence was found that the risk of cancer was decreased, or all­

cause mortality, or longevity differed among those who used vitamin and mineral 

supplements (Kim et al, 1993). As noted in other studies, supplement users were more likely 

to consume more nutrients from their food alone than non-supplement users (Looker et al, 

1988; Merkel et al, 1990; Kim et al, 1993) which affirms the idea that the vitamins people 

choose to take are often not the ones lacking in their diet (Worsley and Crawford, 1984b; 

Merkel et al, 1990). It would appear that those adults who use supplements are unlikely to 

benefit from their use (Looker et al, 1988), nor increase their longevity (Kim et al, 1993). 

2. 6 Children's Studies 

2.6.1 United States Children's Studies 

In the United States, supplement use in children at a national level has only been reported to 

a limited extent, but the data indicates a high prevalence of use. For example, in the 1981 

23 



NHIS Child Health Supplement it was reported that approximately half of the children, from 

birth to six years, had been given a vitamin or mineral supplement in the previous two weeks 

(Kovar, 1982). A similar level of intake was found in the 1986 NHIS; 43% of 2 to 6 year olds 

were given vitamin or mineral supplements within two weeks of the survey (Moss et al, 

1989). Fifty-five percent of all three year olds were given a vitamin or mineral supplement in 

the 30 days prior to the 1991 Longitudinal Follow-up Study (Yu et al, 1997). Non­

representative studies also support the high incidence of supplement use in pre-school and 

school-aged children (Cook and Payne, 1979; Breskin et al, 1985; Krummerys et al, 1995). 

The use of supplements decreases with age. For example, in the 1981 NHIS Child Health 

Supplement, approximately 50% of children in the age range birth to six years, and 36% of 

children under 18 years had consumed a vitamin and mineral supplements in the two week 

period prior to the survey (Kovar, 1982). In NHANES II, it was reported that 39% of two 

year olds and about 11 % of teenagers regularly received a vitamin or mineral supplement 

(Bowering and Clancy, 1986). The decline in supplement use in boys plateaued at around 

10% at 13 years of age while among girls it increased (Bowering and Clancy, 1986). The 

high use of supplements in young children and a decreasing use in older children were 

confirmed in NHANES III; young children 1 to 5 years of age were found to be major users 

of supplements with 42-51 % of toddlers and pre-school aged boys and girls, and between 24-

35% of school-aged children and adolescents respectively took supplements in the month 

prior to the interview (Ervin et al, 1999). 

2.6.2 Other Children's Studies 

The high incidence of supplement consumption amongst pre-school children was also seen in 

a small Canadian study where 63% percent of the mothers gave their children vitamin or 

mineral supplements (Campbell, 1993). In a larger Canadian study, it was reported that 36% 

of 8 to 15 year olds consumed supplements (Whiting et al, 1995). These rates of use were 

comparable to similarly aged children in the United States (Bowering and Clancy, 1986). No 

differences in dietary adequacy, based on nutrients from food alone between supplement 

users and non-users were also reported (Whiting et al, 1995). Both Canadian studies report 

that multi-vitamins were the most commonly consumed vitamins as was found in the 

24 



American studies (Bowering and Clancy, 1986: Campbell, 1993; Whiting et al, 1993; Ervin 

et al, 1999). 

There are very few British children's dietary supplement studies. An Edinburgh study found 

that 25% of pre-schoolers took vitamin or mineral supplements (Payne and Belton, 1992). 

The widespread use of dietary supplements did not appear necessary when the energy intakes 

of 132, 7 to 8 year old Edinburgh school children were found to be in excess of the reference 

nutrient intake (RNI) (Ruxton et al, 1993). Supplement use amongst primary school children 

living in England and Scotland was approximately 16% in the month preceding the National 

Study of Health and Growth (Bristow et al, 1997). This result, and that of the Edinburgh 

study, indicate a lower incidence of use compared with the United States (Payne and Belton, 

1992; Bristow et al, 1997; Ervin et al, 1999). The type of supplement taken, the frequency of 

intake, and a lack of significant gender differences in childhood were all similar to the pattern 

of intake in the United States (Bristow et al, 1997; Ervin et al, 1999). A significant finding 

was that cultural background influenced supplement use, with children of Afro-Carribean, 

Asian or other origins more likely to take a supplement, compared to White English and 

Scottish groups (Bristow et al, 1997). 

Young people in the Netherlands consumed mainly fluoride, vitamin A and D preparations 

which differed from the reported findings in the United States (Dorant et al, 1993; Ervin et al, 

1999). However, as in the United States, increased age was associated with a shift to other 

supplements with Dutch adolescents (Dorant et al, 1993; Ervin et al, 1999). 

Several studies report certain similarities in terms of the key predictors of children's 

supplement use. For example, children with the least need for supplements, as defined by 

socio-economic variables, were more likely to take them (Cook and Payne, 1979; Yu et al, 

1997; Bristow et al, 1997). Young children whose parents received higher education, were 

more likely to receive supplements (Kovar, 1982; Bowering and Clancy, 1986; Dorant et al, 

1993; Bristow et al, 1997) and if the head of the household was White (Bowering and 

Clancy, 1986). In a study of vitamin and mineral supplement use among pre-school children 

in the United States, the following characteristics were identified for mothers who typically 

gave supplements to their children: older, married, insured, had access to private health care, 

25 



and took supplements during pregnancy (Yu et al, 1997). Supplement use by mothers and 

pre-school children was highly correlated (Bowering and Clancy, 1986) as mothers were an 

important role model for children whose supplement practices potentially influenced other 

family members (Merkel et al, 1990; Thomsen et al, 1987). Supplement use in children was 

associated with particular characteristics: first birth order, eating problems or poor appetites 

(Yu et al, 1997). The number of children in the home, and the total number of cigarettes 

smoked in the home, were also significantly associated with supplement use (Bristow et al, 

1997). 

2.6.3 What is Taken? 

In the United States, multi-vitamins, with or without iron and vitamin C, were the most 

commonly consumed supplement by children, as with adults (Cook and Payne, 1979; 

Bowering and Clancy, 1986; Moss et al, 1989; Ervin et al, 1999). Greater numbers of 

children consumed multi-vitamins without iron added, than with iron added (Bowering and 

Clancy, 1986; Ervin et al, 1999). Vitamin C was the second most popular supplement and 

also the most common single nutrient consumed (Bowering and Clancy, 1986; Yu et al, 

1997). Other single nutrients consumed included calcium, fluoride and iron (Moss et al, 

1989). Older children were less likely to take multi-vitamins, and more likely to take single 

or B group vitamins (Bowering and Clancy, 1986; Moss et al, 1989; Ervin et al, 1999). Most 

children consumed only one supplement on a daily basis (Bowering and Clancy, 1986; Moss 

et al, 1989; Krummeys et al, 1995; Ervin et al, 1999) but one study noted that a significant 

proportion of pre-school children consumed two or more supplements (Yu et al, 1997). 

2. 6. 4 Impact of Dietary Supplements in Children 

Few studies have compared biochemical indexes of nutritional status between children who 

do, and do not, take supplements. Improvements were not observed in biochemical indexes 

of several water-soluble vitamins between those who did, and did not, take supplements and 

the mean intakes of nutrients only differed significantly between the two groups when the 

supplements were considered (Breskin et al, 1985). Two studies using NHANES II data and 

26 



different analytical techniques did not find improvements in iron status (Bowering and 

Clancy, 1986; Looker et al, 1987). One study used multiple iron indicators, including serum 

ferritin, in its iron analysis and incorporated sample weights and design effects to avoid 

incorrect point estimates, variances, and test statistics to analyze the complex NHANES II 

design (Looker et al, 1987) which the other study failed to use (Bowering and Clancy, 1986). 

As with adults, children who consumed supplements tended to consume more vitamin C and 

fruit and vegetables than non-supplement users (Bowering and Clancy, 1986). The 

percentage of children who met the RDA for vitamins A and C, thiamin, riboflavin, and 

niacin was greater amongst supplement users than non-users (Cook and Payne, 1979). 

Regular supplement users obtained substantial intakes of some nutrients from vitamin and 

mineral preparations, and supplements probably contributed to an already adequate dietary 

intake for some (Bowering and Clancy, 1986). 

In 1988, Benton and Roberts (1988) published a paper purporting to show that eight months 

of the daily administration of a vitamin/mineral supplement in 30, 12 to 13 year old Welsh 

school children produced a statistically significant increase in non-verbal intelligence 

compared with a matched group receiving a placebo. There were numerous responses to this 

paper (Bates et al, 1988; Bender, 1988; Emery et al, 1988; Hutton and Ashby, 1988; 

MacFarlane, 1988; McNair, 1988; Yudkin, 1988) and the key criticisms were that the 

reported dietary data, based on 3-day diaries, were unlikely to give a true picture of the 

dietary status of the children; that the supplement was not tailored to the subjects' apparent 

needs; and that the association between supplementation and non-verbal intelligence was due 

not so much to the increase of scores in the treated group but to an "adverse" placebo effect, 

ie the failure of the placebo group to increase their scores when in practice the average score 

would be expected to increase on the repeated administration of the tests (Bates et al, 1988; 

Bender, 1988; Hutton and Ashby, 1988; MacFarlane, 1988; McNair, 1988; Yudkin, 1988). 

From the work published to date, there is little to suggest that the diets of most western 

children who are seen to be growing adequately are so deficient in micro-nutrients as to 

impair their mental functioning (Nelson, 1992). However, there may be a proportion of 

children whose diets are poor, and whose poorer performance on intelligence tests could 

theoretically be due to marginal nutrient deficiencies, independent of the effects of social 

27 



class, parental education, or other confounding factors, but the evidence for such an 

association is weak (Nelson, 1992). 

2. 7 Why Supplements are Taken? 

2. 7.1 Key Findings 

Few studies have examined the reasons for supplement use. In NHANES I, Block et al 

(1988) identified the health habits and beliefs, and the key socio-demographic variables, that 

influence an individual's supplement intake (Block et al, 1988). The following factors 

influenced supplement intake: 

1) Individuals who, believed that diet affects disease, were significantly more likely to 

be regular supplement users, than those who did not. 

2) Non-drinkers and lighter drinkers were somewhat more likely to use supplements 

than were heavier drinkers. 

3) Never and former smokers were more likely to be supplement users than were current 

smokers. 

4) Individuals in the highest quartile of body mass index were less likely to use 

supplements than were those in the other three quartiles (Block et al, 1988: p302). 

Similar results were found from alcohol intake, smoking, and body mass index in NHANES 

II (Kaplan et al, 1986). Supplement practices were related to people's physical and emotional 

states of health, as well as their dietary habits, food, and nutritional beliefs (Worsley and 

Crawford, 1984b). Supplement use was also associated with control over health and sense of 

well being (Kim et al, 1993) and positively correlated with good health (Bender et al, 1992). 

Control over one's health included the attempt to prevent minor illnesses, perceived dietary 

deficiencies through an unbalanced diet, or negative perceptions of the food supply, and 

perceived health benefits to prevent degenerative diseases (Fleischer and Read, 1982; 

28 



Schultz, 1982; Worsley and Crawford, 1984b; Levy and Schucker, 1987; Merkel et al, 1990; 

Bender et al, 1992; Kim et al, 1993). 

Supplements were also consumed because of medical advice, menstrual and hormonal 

problems, maternal influence, adherence to vegetarian food patterns, and peer 

recommendation (Fleischer and Read, 1982; Schultz et al, 1982; Bowering and Clancy, 1986; 

Sobal and Marquart, 1994a; Yu et al, 1997; Ervin et al, 1999). Statements such as: to provide 

energy, to promote weight loss or weight gain, or to help with sport were also given as 

reasons for supplement use (Fleisher and Read, 1982; Schultz, 1982; Sobal and Marquart 

1994a). 

People who regularly supplement their diet appeared health oriented and used diet, among 

other means, to ameliorate their health (Worsley and Crawford, 1984b; McMahon, 1998). 

These people perceived their health in a worse light than other people and were more 

accepting of general and specific claims about the benefits associated with vitamins and 

minerals (Worsley and Crawford, 1984b). Only a small number of sampled supplement users 

indicated that the supplements they consumed were of little or no value (Read et al, 1989). 

In the United Kingdom, the pattern of supplement consumption in children was more related 

to beliefs and cultural background than health needs (Bristow et al, 1997). In contrast in 

Canada children 's supplement use was related to possible dietary deficiencies (Campbell, 

1993) and in the United States to behavioural traits (Yu et al, 1997). Children with the least 

need for supplements were the most likely to receive them (Bowering and Clancy, 1986; 

Bristow et al, 1997). 

2.8 The Limitations of Supplement Use 

2.8.1 Supplements: Health, Well-Being and Resistance to Disease 

The major chronic diseases in Western societies have multiple causes. The advent of 

antibiotics and vaccines led many people to think that the cure of these diseases awaited 

specific "magic bullets" and some proponents of supplements feel that supplements are the 

29 



nutritional "magic bullets" for heart disease, and other maladies (Thomas, 1996). While 

Americans are a nation hungry for simple nutritional solutions to complex health problems 

(Brody, 1995), others warn against thinking in a penicillin mode (Golub, 1994). This can be 

easily done in nutrition because the first identified nutrient-related diseases were caused by 

deficiencies, but there are no simple cause and effect relationships for cardiovascular disease, 

cancer, stroke, diabetes or osteoporosis (Thomas, 1996). Vitamin E is an example of a 

nutrient that may, or may not, influence the risk of developing heart disease; for some people, 

it may be potentially important, but for others, it is at best one factor, probably not a major 

one (Thomas, 1996: p47). Genetic inheritance is a primary contributor to chronic disease risk 

as "genes have a powerful influence over body size and disease risk, and though diet helps 

temper unwanted tendencies, who you are is often more important than what you eat... 

Because of genetics, diets help some people a lot, some people a little, and a very few people 

not at all" (Hisler, 1995: p49). The other factors that are influential include the risk of chronic 

disease are exercise, smoking, alcohol consumption, stress levels, rest and relaxation, and 

eating a diet that meets the and dietary guidelines (Thomas, 1996). Genetic inheritance, and 

these lifestyle factors , influence our health and disease, not the use of supplements (Thomas, 

1996). 

2.8.2 Food: More Than the Sum of its Nutrients 

Food constituents and compounds that are not classical nutrients can apparently influence 

health and disease (Thomas, 1996; ADA, 1996). Phytochemicals, which include flavonoids, 

monoterpenes, phenolics, indoles, allyic sulphides and isothiocyanates are examples. Their 

roles in improving health, treating disease, or extending life are, as yet, only ideas for 

research which reinforces the preference of most public health and nutrition scientists for 

people to obtain their nutritional requirements from food (Thomas, 1996). 

2.8.3 Intervention Supplement Studies 

Epidemiology studies show that fruit and vegetable consumption reduces the risk of lung 

cancer in smokers from foods containing beta-carotene and many other carotenoids and 

30 



phytochemicals. A summary of these studies can be found in van Poppel and Goldbohm (van 

Poppel and Goldbohn, 1995). However, epidemiology studies can only identify whether the 

variables under study are related in some way to an outcome. The following studies are 

recent clinical trials of single nutrients where subjects were randomly assigned to a treatment 

or a control group to help to identify a cause-and-effect relationship. 

The Alpha-Tocopherol Beta-Carotene (A TBC) Study sought to determine whether daily 

supplements with alpha-tocopherol, beta-carotene, or both, would reduce the incidence of 

lung cancer and other cancers. A total of 29,133 male smokers 50 to 69 years of age were 

randomly assigned to one of four daily regimens; 50mg alpha-tocopherol, 20mg beta­

carotene, both alpha-tocopherol and beta-carotene, or placebo. No reduction in the incidence 

of lung cancer was seen after 5 to 8 years of supplementation of alpha-tocopherol or beta­

carotene but the possibility was raised that these supplements may actually have harmful as 

well as beneficial effects (The Alpha-Tocopherol Beta-Carotene Study Prevention Group, 

1994). 

In the Beta-Carotene Retinal Efficacy Trial (CARET), 18,314 smokers, former smokers and 

workers exposed to asbestos took either daily supplements of combined 30mg of beta­

carotene, 25,000 IU vitamin A, or a placebo to compare the incidence of lung cancer. After 

an average of four years supplementation, the study was halted because no clear benefits 

were seen, and those who received the supplements had a higher rate of death from lung 

cancer and heart disease (Omenn et al, 1996). 

In the Nurses Health Study (NHS), a prospective cohort of 87,000 female nurses were 

studied from 1980 to 1988 for cardiovascular disease. A 34% reduction in the risk of 

cardiovascular disease was found after adjustment for age and smoking amongst women who 

consumed high supplementary intakes of vitamin E, which were greater than lOOIU/day 

(Stampher et al, 1993). The Health Professionals Follow-up Study, another cohort 

prospective study, followed approximately 40,000 men aged 40 to 75 years who were free of 

cardiovascular disease, diabetes, or cholesterol for four years. The contribution of vitamin E 

from foods and from supplements was examined separately. After a four year follow-up, a 

significant reduction in the risk of coronary disease was limited to those with an intake of 

31 



vitamin E that was greater than lOOIU/day from supplements. In both this study and the 

NHS, short-term use was not associated with any obvious benefit (Stampher and Rimm, 

1995). In the Physicians Health Study (PHS), 22,071 physicians of whom 11 % were current 

smokers and 39% were former smokers took either 50mg beta-carotene or a placebo on 

alternate days. Twelve years of supplementation with beta-carotene produced neither benefit 

nor harm for cancer or heart disease among these healthy men (Hennekens et al, 1996:pl). 

When the results of CARET were combined with those of the ATBC Cancer Prevention 

Study and the PHS, it became clear that there could be little confidence in the efficacy, or 

safety, of supplemental beta-carotene or vitamin A in efforts to reduce the burdens of cancer 

and heart disease in certain populations (Omenn et al, 1996). The results of these studies 

counter the claim that taking supplements protects the health of those who do not eat, or take 

care as much as they should and, also that science cannot be rushed (Thomas, 1996). 

In contrast, the Nutrition Intervention Trials in Linxian, China, involved the measurement of 

cancer and mortality incidence among 29,584 adults who received daily vitamin and mineral 

supplementation during a five year period. The subjects were randomly assigned to four 

intervention groups: retinol and zinc; riboflavin and zinc; vitamin C and molybdenum; and 

beta-carotene, vitamin E and selenium. A significantly lower total mortality risk occurred 

among those receiving supplementation with beta-carotene, vitamin E, and selenium (Blot et 

al, 1993). However, Linxian is an area known historically to have limited food availability 

and variety and the subjects were a very different population from those examined in other 

studies (Omenn et al, 1996). 

2.8.4 Dietary Supplements: A Potential Source of Toxicity 

Nutrients, like all other substances, can produce adverse effects if intakes are sufficiently 

high (Hathcock, 1993) and these vary widely from nutrient to nutrient and may vary with the 

age of the individual (The American Institute of Nutrition and American Society of Clinical 

Nutrition, 1987). "Mega-vitamin therapy" described as the consumption of vitamins in 

amounts of more than 10 times the recommended intake (Woolliscroft, 1983) is rejected by 

others (Basu Dickerson, 1996) as a misnomer because no clear definition or dose limit exists. 

32 



Vitamins taken in such high doses act more like drugs than nutrients (Basu and Dickerson, 

1996). Mega-mineral therapy describes those instances in which minerals were taken in 

amounts above recognised biologic requirements (CPS, 1990). Mega-vitamin and mega­

mineral regimens are advocated as "natural therapies" by various lay healers, although there 

has been little scientific evaluation of these therapies (CPS, 1990). Those who take dietary 

supplements unsupervised can therefore face the possibility of toxicity. High-dose tablets, 

described as "high potency" to convey an aura of acceptability, illustrate this possibility. In 

children, the major concern is the oversupply of vitamin A and vitamin D, and to a lesser 

extent, iron and calcium which reflects the interplay between availability and toxicity (CPS, 

1990). Iron supplements intended for other household members are the most common cause 

of paediatric poisoning deaths in the United States (The United States Preventative Services 

Task Force, 1993). 

2.8.4.1 Fat-Soluble Vitamins 

Fat-soluble vitamins tend to cause toxic reactions at lower multiples of the RDA than do 

water soluble vitamins because they are stored in the body, rather than excreted if taken in 

excess for a long period of time (Basu and Dickerson, 1996). Evidence of the adverse effects 

of vitamin A is usually associated with intakes greater than 7500ug retinal equivalents (RE) 

or 25,000 international units (IU) (Hathcock, 1997). Vitamin A analogues, used in the 

treatment of acne, are also known for their teratogenic effects (Hall, 1984). The effects of 

alcohol or high intakes of retinal have been offered as an explanation for the adverse 

outcomes with beta-carotene in the A TBC and the CARET trial (Al banes, 1996). Sub-group 

analysis of the ATBC and CARET data indicated that the hazardous-promoting effects of B­

carotene were seen primarily in subjects who consumed alcohol and smoked more (Albanes 

et al, 1996; Omenn et al, 1996). Lachance (1998b) suggests that because epidemiological 

results are strongly supportive of the role of anti-oxidants in the defence of oxidative insults, 

any results from intervention trials of the long-term oxidative insults of smoking which 

questionably incriminate beta-carotene to be a hazardous chemical must be viewed with 

caution (Lachance, 1998b:p35). He argues that both the ATBC and CARET studies failed to 

consider the interplay of anti-oxidant nutrients or include toxic amounts of compounds that 

33 



promoted a co-morbidity outcome leading to both lung cancer and liver pathology that 

resulted from heavy smoking and (a) alcohol consumption (A TBC) or (b) toxicity of vitamin 

A (CARET) (Lachance, 1998:p35). In adults, vitamin D intakes of 10,000IU for several 

months resulted in marked disturbances in calcium metabolism (Woolliscroft, 1983). Intakes 

of 2000-3000IU/day of vitamin D caused "idiopathic hypercalcemia" in children (Forfar at 

al, 1956). 

2.8.4.2 Water-Soluble Vitamins 

Thiamin, riboflavin, vitamin B12 and biotin do not seem to cause toxic reactions in humans 

when taken in large doses orally (CSA, 1987). Nicotinic acid, taken to lower serum lipids, 

can produce liver toxicity when gram quantities are taken (Rader et al, 1992). Large doses of 

vitamin B6, used in the treatment of premenstrual syndrome, can cause sensory neuropathy 

(Schaumburg et al , 1983), although women vary considerably in their sensitivity to the 

vitamin (Dalton, 1985). 

Vitamin C and beta-carotene are both anti-oxidants. At physiologic levels, ascorbate acts 

primarily as an anti-oxidant. As pharmacologic levels are reached, its pro-oxidant effects 

predominate (Repka and Hebbel, 1991). In the presence of iron, excess vitamin C is a very 

potent pro-oxidant that converts iron stores to catalytic iron, a very oxidant substance 

(Herbert, 1992). Ascorbic acid enhances iron absorption from the digestive tract. In those 

who are genetically susceptible to iron overload, this can lead to haematochromatosis (Basu 

and Dickerson, 1996). It has been suggested that with high levels of stored iron, serrum 

ferritin is a risk factor for coronary heart disease (Salonen et al, 1993). However, this work 

has not been substantiated. Vitamin C in doses greater than 500mg can be harmful to people 

with a predisposition to form oxalate stones (Levine et al, 1996). There has been speculation 

that high doses of ascorbic acid could result in adaptation to the high intake, resulting in 

greater than normal metabolism of the vitamin and lead to "conditioned scurvy" when the 

high intake is discontinued, but these claims have not been substantiated (Hathcock, 1997). 

Although no toxic affects of folate have been clearly established, consuming excessive 

amounts of this vitamin can mask a vitamin B12 deficiency and could delay the diagnosis of 

pernicious anaemia, with irreversible neurological damage (Basu and Dickerson, 1996). 

34 



While the safe intake level of many trace elements has not been defined, an excess clearly 

may lead to toxic effects (O'Dell, 1984; CPS, 1990). As trace elements may share a common 

transport and enzyme system, there is concern that the ingestion of excessive quantities of 

one trace element may reduce the absorption of others (CPS, 1990). For example, while large 

amounts of zinc caused toxicity, lower intakes of zinc (still in excess of the RDA) interfered 

with the utilization of copper and iron, and adversely affected high density 

lipoproteincholesterol concentrations (Fosmire, 1990). Zinc therapy has also induced copper 

deficiency (Prasad et al , 1978). 

2.8.5 Adverse Nutrient Interactions 

Nutrients derived from food, and not supplements, are less likely to contribute to adverse 

interactions with medical care (ADA, 1996). Little information is available to demonstrate 

that long-term, and possibly lifetime intakes, of large doses of supplements are completely 

safe as studies on the consequences of large nutrient intake in humans rarely have a large 

sample size and rarely go beyond several months (Thomas, 1996). Many problems associated 

with doses of single nutrients reflect interactions that result in a relative deficiency for 

another nutrient. For example, vitamin E acts synergistically with anti-coagulant drugs 

(Bendich, 1992). High amounts of calcium inhibit the absorption of iron (Cook et al, 1991). 

Very large doses of beta-carotene decreased the concentration of lycopene, another important 

carotinoid in the low-density lipoproteins, by 12-25 % (Graziano et al, 1995). Tryptophan 

supplements have been associated with eosinphilia-ayalgia syndrome, a connective tissue 

disease (Roufs, 1992; ADA, 1996). 

2.9 Vitamins, Minerals and Exercise Performance 

2.9.1 Impact of Vitamins and Minerals on Exercise Performance 

What are the effects of sport and exercise on vitamin and mineral status? Does physical 

training result in vitamin and mineral deficiencies? Are the vitamin and mineral requirements 

35 



of athletes increased? Moderate physical activity does not adversely affect vitamin and 

mineral nutritional status when recommended amounts of vitamins and mineral elements are 

consumed in the diet (Clarkson, 1991b; Keith, 1989; Lukaski, 1995). A heavy exercise 

programme may increase requirements for some nutrients, including B group vitamins and 

iron, but athletes involved in such programmes would benefit from nutritional counselling 

(Burke and Read, 1993). When athletes typically consume a well balanced diet, they exceed 

their RDA!RDI levels (Faber and Spinner-Benade, 1991; Sobal and Marquart, 1994b; Brill 

and Keane, 1994). Many studies have found that most adult athletes consume high calorie 

diets with adequate amounts of vitamins and minerals and have little need for 

supplementation (Nieman et al, 1989; Keith, 1989; Lane, 1989; Clarkson, 1991 b; Lukaski, 

1995). The situation is different for those athletes who are on weight loss diets, have poor 

dietary habits with restricted variety in their diet, have limited access to food, or have eating 

disorders (Moffat, 1984; Clarkson, 1991a; Burke and Read, 1993). Poor dietary habits 

associated with the maintenance of low body weights are more likely to be found in sports 

that may promote unrealistically low body fat levels, and where fad diets and eating disorders 

are more common, in the case of dancers, gymnasts and wrestlers (Clarkson, 1991a, Burke 

and Read, 1993). These athletes may be unwilling to increase their energy intake to satisfy 

RDA levels. Supervised supplementation of vitamins and minerals may be required in cases 

of on-going sub-optimal dietary intake or to meet short-term goals (Burke and Read, 1993; 

Armstrong and Maresh, 1996). 

2.9.2 Supplements: Nutritional Aids to Exercise Performance and Health 

During the past two decades, Americans have been encouraged to increase their levels of 

physical activity as a means of preventing chronic disease and enhancing their quality of life 

(Lukaski, 1995). Sport can be a leisure activity for participants and provide exercise 

(American College of Sports Medicine, 1990). In New Zealand, the importance of physical 

activity to health has also been expounded by experts and maintaining health was given as 

the main reason for participation in physical activity by 72% of those surveyed in the Life in 

New Zealand Survey (Russell et al, 1991). In the past, there has been confusion between the 

relationship of nutrition, exercise and sport, which has arisen from misinformation, 

36 



misconceptions and unrealistic expectations and can usually be traced to lack of fundamental 

knowledge and recent research findings (Dreizen, 1989). Nutrients such as carbohydrates and 

water have been used by athletes to maintain and enhance endurance performance (Burke and 

Read, 1993) but misconceptions still exist about the relationship between vitamin and 

mineral supplements and exercise performance (Clarkson, 1991b; Kies, 1995). 

2.9.3 Vitamin and Mineral Status of Athletes 

Food intake can be monitored to assess vitamin and mineral intake. Dietary records, although 

unreliable in some circumstances, can increase the knowledge base for both athletes and non­

athletes in population groups (Short, 1989). Dietary adequacy can be addressed by a 

comparison of the dietary record with the RDAs but these vary from country to country as 

they are established independently. For example, the RDA for adult men for vitamin C in the 

United Kingdom is 40mg (Ministry of Health, 1998) and in the United States, it is 90mg 

(Nutrition Today, 2000). Studies used to set the RDAs did not include athletes nor was the 

exercise status of the individual reported (Clarkson, 1991a) which questions the accuracy of 

using the RDA to evaluate the nutritional needs of the athletes (Sirota, 1994). 

The status of the body content of certain vitamins and minerals can be more accurately 

assessed by clinical signs, tissue or blood samples analysis than with dietary records. Tissue 

analysis accurately documents specific deficiencies, but involves invasive and costly 

techniques. Vitamin levels can be measured directly from blood serum or plasma, or 

indirectly by an assessment of erythrocyte enzyme function (Clarkson, 1991b). These 

techniques are also associated with problems. For example, two different methods used to 

measure thiamin status in the blood yielded different results (Guillard et al , 1989). Test 

accuracy can be questionable. For example, t