The media bombard us with new vitamins that boast a cure to the aches and pains of everyday living, banish those niggling ailments and quash the nagging thoughts in the back of your mind telling you your lifestyle should be healthier. These self prescribed vitamins have become a part of UK health.
But are self prescribed vitamin supplements improving UK health? Dr Geoff weighs up the facts:
Around 30% of British adults use vitamin-containing supplements.
They may be taken to:
– ensure dietary adequacy;
– compensate for some (perceived) extra need;
– treat or prevent illness (even though medicinal claims for supplements are technically illegal);
– enhance athletic performance.
Average UK adult intakes of all vitamins from food are above the level that is taken to “guarantee” adequacy. Nevertheless substantial numbers of people record intakes that are inadequate or have biochemical evidence of deficiency.
Vitamin supplements increase average intakes but make no difference to the numbers with inadequate intakes; they are taken by those who don’t need them. Some researchers have falsified clinical trial data to boost sales of their supplements.
Under clinical trial conditions supplements of folic acid taken before pregnancy greatly reduces the incidence of spina bifida and anencephaly (Neural Tube Defects*). They are effective only if taken very early in pregnancy and probably most effective if taken pre-conceptually. Since 1992 women contemplating pregnancy have been advised to take folic acid supplements and all sexually active premenopausal women are now advised to take them.
Supplement advice has had no measurable impact upon the incidence of NTD (Neural Tube Defects*). Very few women take folic acid supplements routinely (those who need them least) and, as many pregnancies are not specifically planned, they are usually taken too late.
Fifty countries have fortify bread or flour, with folic acid and this has produced sharp and immediate falls in NTD incidence. However, fortification exposes several hundred thousand people to the extra folic acid for each affected pregnancy prevented. Is folic acid absolutely safe? Might fortification be justified by wider benefits?
People who consume diets rich in antioxidant vitamins (A, C, and E) or spontaneously take vitamin E supplements have reduced risk of cancer and heart disease. Many reductionist studies and animal studies also highlight short term claimed “benefits” of antioxidants. Despite this mass of observational and reductionist evidence, controlled trials of antioxidant supplements fail to show any beneficial effects upon cancer, cardiovascular or total mortality. Some trials have found increased mortality in the supplemented group especially for β-carotene (a form of vitamin A) in smokers. Many antioxidant studies have commercial sponsors and seem designed to produce positive results i.e. aimed more at generating sales-promoting media headlines for their product than advancing scientific knowledge.
*Neural tube defects are birth defects of the brain, spine, or spinal cord.
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