Uses of supplements

There are two main approaches to the use of supplements. They can be used to:
• treat or prevent nutritional deficiency; and to
• reduce the risk of non-deficiency disease and promote optimal health.

When vitamins were first discovered during the early years of the 20th century, their only indication was for the prevention and treatment of deficiency disease such as scurvy, beri-beri, pellagra, etc. This led to the development of dietary standards such as RDAs and, more recently, to the Dietary Reference Values (DRVs).

These values were based on amounts of nutrients required to prevent deficiency, and even though subject to various limitations, they are still the best measure of dietary adequacy. After the Second World War, it was thought that nutritional deficiencies had largely disappeared and scientific interest in vitamins and minerals waned. However, with the increase in various chronic diseases such as cardiovascular disease and cancer, vitamins became an area of growing interest again, and itwas suggested that supplements might help to reduce the risk of such disease. At the start of the 21st century, there is growing concern among the public to improve quality of life and supplements are increasingly used to promote so-called optimum health. Despite the idea that nutritional deficiency had disappeared, recent UK national diet and nutrition surveys have shown that there is no room for complacency. Although average dietary intakes may appear adequate, some groups of the surveyed populations are clearly at risk of marginal deficiencies. The National Diet and Nutrition Survey in preschool children4 showed that 8%of the surveyed youngsters aged 11 /2 to 41 /2 were anaemic, a further 12% were mildly iron-deficient and 15% had a poor intake of zinc. Vitamin A deficiency was present in 8%, vitamin B2 deficiency in 23% and vitamin C deficiency in 3%. A similar nutritional survey of older children again showed average nutrient intakes were largely fine, but anaemia was present in 1.5%of boys and 5% of girls, with respective totals of 13% and 27% having low serum ferritin – an indication of iron deficiency. In addition, zinc was found to be low in the diets of 10%of boys and 20% of girls. Also of concern were calcium intakes, which were below the Lower Reference Nutrient Intake (LRNI) in 6%of boys and 12% of girls. For magnesium, the respective figures were 12% and 27% and for vitamin A, 10% and 11%. Furthermore, some of the surveyed youngsters also appeared to have poor status for vitamin B12, vitamin C, vitamin D, folate, riboflavin and thiamine.

The National Diet and Nutrition Survey of people aged 65 years and over6 showed that there were nutritional problems in some individuals. Up to 38%of the survey population was deficient in vitamin D, up to 38% were deficient in vitamin C, up to 18% in folate, up to 15% in vitamin B12 and up to 30% in iron. Of the free-living individuals, 11% of men and 9% of women were anaemic. The most recent National Diet and Nutrition Survey involving British adults aged 19–64 years1 found that mean intakes of all nutrients in men are ≥ 100% of the RNI. For women, mean intakes of iron, magnesium and copper were below the RNI. However, mean intakes fail to show the proportion of people that do not achieve the RNI. For example, for women, mean magnesium intake was 85% of the RNI, but 74% in this survey failed to achieve the RNI.Mean intakes also fail to show that intakes in some age groups are particularly poor. For example, iron intake inwomen overall was 82% of the RNI while in 19–24-year-old women it was 60% of the RNI. Overall, 91% of women failed to achieve the RNI for iron while 41%of women aged 19 to 34 had intakes of iron below the LRNI. For magnesium and copper, intake overall in women is 85% and 86% of the RNI, respectively, but for women aged 19–24 years it was 76% of the RNI for both minerals. Indeed, men and women aged 19–24 had significantly poorer intakes of all vitamins and minerals than those aged 50–64, with mineral and trace element intakes in the women aged 19–24 years a particular cause for concern. Although good diet is the most appropriate route to achieving improved nutrition in these population groups, there is no evidence to suggest that risk of deficiency is a thing of the past.

Various groups of the population could be at risk of nutrient deficiency and could benefit from supplementation. These include:
• People in a particular demographic category, e.g. infants and children, adolescents, women during pregnancy and lactation and throughout the reproductive period, the elderly and ethnic minorities.
• People whose nutritional status may be compromised by lifestyle (enforced or voluntary), e.g. smokers, alcoholics, drug addicts, slimmers, strict vegetarians (i.e. vegans), food faddists, individuals on low incomes and athletes.
• People whose nutritional status may be compromised by surgery and/or disease, e.g. malabsorption syndromes, hepato-biliary disorders, severe burns and wounds and inborn errors of metabolism.
• People whose nutritional status may be compromised by long-term drug administration(e.g. anticonvulsants may increase the requirement for vitamin D).

Increasingly, people are taking supplements for reasons other than prevention of deficiency and at amounts higher than the RDA. Moreover, evidence is increasing that, at least for some nutrients (e.g. folic acid, vitamin D), there may be benefits in achieving higher intakes than the RDA. However, while there is agreement about the beneficial effects of nutrients in the prevention of deficiency disease and the amounts required to achieve such effects, there is controversy about amounts required for reduction in risk of chronic disease and so-called ‘optimum health’. Some would argue that higher amounts are required and that basing requirements for nutrients only on the prevention of deficiency disease is inadequate. But what other end points should be used is open to debate; longevity increased resistance to cancer and coronary heart disease, improved athletic performance etc. Higher levels of intake cannot always easily be obtained from diet alone, and supplementation is required. However, excessive intake of some nutrients can lead to toxicity, and it is with this in mind that several committees worldwide have established safe upper limits for supplement intake.