Panic: ‘Vitamins “could shorten lifespan”’ says BBC News, among many others, reporting on a study by researchers at Copenhagen University published in the Journal of the American Medical Association. The researchers examined over 800 clinical trials into the benefits of vitamins A, E, and C, alongside beta-carotene and selenium - all commonly-used supplements. From these, 68 were selected on the basis of being most likely to give an accurate assessment of vitamin benefits. No negative or positive effect was found on mortality. When a further 21 studies were included, it was found that three supplements might actually increase mortality: beta-carotene (seven per cent increase), vitamin E (four per cent increase) and vitamin A (16 per cent increase).

The researchers conclude: ‘Considering that 10-20 per cent of the adult population in Europe and North America may consume the supplements, the public health consequences may be substantial.’

Don’t panic: The results of this study are utterly feeble and drawing any conclusions from it would be most unwise. Reports that find increases in risk of less than 100 per cent have to be treated, at the very least, with caution because there are so many potential confounding factors. These results are much weaker than that and should be discounted.

Bringing together so many studies into a meta-analysis has some advantages in terms of reducing the possibility of any findings being due to chance. However, that assumes that the different studies included are truly comparable. It is interesting to note that the researchers found no effect in the 68 studies they themselves thought used the best methods but had to add in other, less reliable studies, to produce any statistically significant results.

Based on this study and others, anti-oxidant vitamin supplements have no effect on life expectancy one way or another unless they are taken to excess. There was hope that such supplements might have some positive impact on heart disease, but this has not been borne out.

What the discussion about vitamins does reveal is an obsession with trace quantities of chemicals in our diets. On the one hand, proponents of supplements say that we should all take these pills to prevent heart disease, cancer and ‘boost our immune systems’. On the other hand, mainstream advice has been that they are unnecessary if you eat a ‘balanced diet’.

Unfortunately, what a ‘balanced diet’ means is bound up with all sorts of rules about eating five portions of fruit and vegetables for vitamins and fibre, oily fish for those omega-3’s, olive oil for those monounsaturated fats, red wine and tea for anti-oxidants… the list goes on and on. And then there’s all the food you’re supposed to avoid: red meat, saturated fat, trans fats. No wonder people conclude that popping a couple of pills is simpler.

There’s something neatly rational about vitamin pills. They suggest that our nutrition is simply a matter of ensuring the correct quantities of a few chemicals, and that these can easily be provided in an inert one-a-day pill. They’re a nice idea - but probably unnecessary even if you don’t follow that mythical ‘balanced diet’.

Vitamins ‘could shorten lifespan’, BBC News, 28 February 2007