We swallow them by the bucketload at great expense but there is no evidence vitamin supplements do us any good, and they may even be doing us harm, scientists have concluded.
In a blow to the multimillion pound dietary supplement industry, a review of 67 randomised trials of vitamin pills has found that far from prolonging life, they may actually shorten it.
There is "no convincing evidence" that antioxidant supplements cut the risk of dying prematurely and some of the commonest ones may increase the risk of early death, according to the review, published by The Cochrane Collaboration.
One in three women and one in four men in the UK are estimated to take vitamin pills to ward off disease. Despite several studies warning of potential dangers, the industry continues to thrive.
The latest review, one of the largest involving 232,000 participants, compared those taking the supplements with those who took a placebo or received no treatment. The supplements studied were beta-carotene (a precursor of vitamin A that is converted into the vitamin in the body), vitamin A, vitamin C, vitamin E and selenium.
Goran Bjelakovich, the visiting researcher who led the systematic review at Copenhagen University, said: "We could find no evidence to support taking antioxidant supplements to reduce the risk of dying earlier in healthy people or patients with various diseases."
"The findings show that, if anything, people in trial groups given beta-carotene, vitamin A and vitamin E showed increased rates of mortality. There was no indication that vitamin C and selenium may have positive or negative effects; we need more data [on these]."
The researchers separated out the 47 trials with a low risk of bias and in these they found a significantly increased death rate. When taken separately, vitamin A was associated with a 16 per cent increased mortality, beta-carotene with a 7 per cent increase and vitamin E with a 4 per cent increase. For vitamin C and selenium there was no significant increase or decrease in the death rate.
Dr Bjelakovich said: "The bottom line is that current evidence does not support the use of antioxidant supplements in the general healthy population." The researchers were unable to explain their findings but said "excessive antioxidants can adversely affect key physiological processes".
Yesterday, Pamela Mason, of the Health Supplements Information Service, said: "Trials using antioxidant supplements have shown inconsistent findings and yet another review is not going to tell us anything at this stage that we do not already know."