Do vitamin supplements really work?

Asked by: Carole Cooper, Southampton. Answered by: Dr Jeya Henry, Professor of Human Nutrition and Director of Functional Food Centre, Oxford Brookes University

In the beginning

From the regulation of the metabolism, the conversion of fats to energy, the formation of bones and teeth, through to the production of sperm, vitamins play an essential role in most cellular processes.

It comes as a surprise to many then, that the term "vitamin" was unknown until the beginning of the 20th century. A Polish scientist by the name of Casimir Funk was the first person to give the nutrient he had isolated from rice husks a name. Combining the Latin term for life, vita, and a compound called an anime, he coined the name vitamin.

The great leap forward

Twenty years after this discovery in the mid-1930s, the first vitamin supplements came on to the market. However, it wasn't until the 1970s and the advocacy of Linus Pauling, double Nobel laureate and eminent chemist, that they leapt to popularity.

Pauling contended that "auto-molecular vitamin C dosing", as he called it, was a panacea that reduced not only the incidence of cancer but also heart disease. The suggestion is that at a certain dose it acts as an anti-oxidant which protects cells from oxidative damage bought about by the bombardment of the body by free radicals. However, while there have been observational studies to support such a notion, there has been little definitive proof.

The usefulness of supplements

What is not in doubt, though, is that supplements are, in some instances, extremely useful. While eating a varied and balanced diet is the best way to get the micronutrients the body requires, some essential vitamins are difficult to come into contact with naturally. Vitamin D, for example, is acquired through exposure to sunlight, which is sometimes hard to come by in northern European countries; having a supplement available which contains your daily allowance is extremely useful in such circumstances. Likewise, taking folic acid supplements is recommended for pregnant women, as it helps prevent neural-tube defect in babies. In such circumstances there is clear evidence that demonstrates the utility of vitamin supplements.

We need to bear in mind, though, that supplements were originally conceived as a means to appease a deficiency rather than act as a cure-all. The recommended daily allowance [RDA] – the mean quantity needed for a healthy person +2 standard deviations – is the product of this need. Often, vitamin tablets contain many times a person's RDA and it is unclear, from a scientific perspective, if there is any value in taking such quantities. That said, if intake falls within the zone of safety it may be worth it. After all, if there is a chance that taking a relatively cheap vitamin C tablet helps ward off atherosclerosis, then its is surely worth the gamble. It is, in most cases, best to see hyper-dosing of vitamins as an insurance policy.

Health concerns

It is possible, however, to overdose on vitamins. While a surfeit of a water-soluble vitamin, such as C, is seldom dangerous as it can be expelled via the urine, it is much harder to expel excess quantities of fat-soluble vitamins. Vitamin A is a case in point. In large doses it has the potential to accumulate in body fat, especially in the fatty tissue around the liver. The toxic effects of this can be severe, causing headaches and dizziness and in pregnant women adversely affecting the foetus.

But, again, that is not to say one shouldn't take supplements; merely that one should take care to confine oneself to the recommended daily allowance.

Proving their worth

An increasing quantity of research is being commissioned which explores the incidence of certain diseases and diet – and some of the most interesting of this centres on vitamin consumption. The new research on vitamin B and its effect in slowing the onset of Alzheimer's is extremely encouraging from a public health point of view. After all, the cost of supplying the supplement is minuscule in relation to the benefits accrued.

Equally exciting is the new research linking vitamin D consumption and a reduction in the symptoms of diabetes. With supplements readily available the potential to change the lives of sufferers is immense and relatively inexpensive. Supplements have often proved their worth over the last century, and it is to be hoped that with new research these inexpensive pills can change even more lives.

Interview by Samuel Muston