Trade bodies such as the Council for Responsible Nutrition refuse to accept the Cochrane methodology and believe a witch-hunt is going on.

"This latest attempt to discredit antioxidants does nothing to change the practical implications for consumers, specifically a generally healthy population, that uses antioxidant supplements as part of their proactive optimum health regimen in an attempt to fill nutrient gaps or help reduce the risk of chronic disease," it says in a statement.

It's not the first time the Cochrane team has turned its guns on antioxidants. It started with a review of supplements used to try to prevent gastrointestinal cancers, which was published in the Lancet medical journal in 2004.

The team found 14 trials of generally high quality - and found that antioxidant supplements, far from preventing these cancers, made it more likely people would die of them.

The result was the latest paper, an updated form of a study that was originally published a year ago in the Journal of the American Medical Association. It has also now been officially released by the Cochrane Library.

The idea that vitamins could lengthen life is, as are all good theories, based on perfectly reasonable observations. Antioxidants fight cell damage.

The Food Standards Agency in the UK says that a healthy diet should give anybody who is well all the antioxidants they need, and warns that high levels of some vitamins can be damaging. Most people in the well-fed developed world probably do not need extra vitamins or minerals. But a lot of us can't shake what we heard at our granny's knee - that vitamin C prevents a cold, for instance (recently disproved by yet another Cochrane review).

Vitamins have attracted a cult-like following. Linus Pauling, the US scientist who won two Nobel prizes, famously extolled vitamin C, convinced that large doses (more than 1g a day) would cure cancer. An institute in his name at Oregon University pursues his theories still.

And so the debate goes on, with large numbers of people convinced a bit more of what is good for you can't do you any harm and scientists using methodological techniques that only scientists understand to prove them wrong - only to be disbelieved. In the end, maybe the safest thing is just to eat a better diet.

(China Daily 04/23/2008 page19)