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Antioxydants: no proven preventive effect, and some even increase mortality

In the absence of an obvious deficiency, antioxydants (vitamin E, carotene, etc.) have no proven health benefits, and some are probably harmful.

An initial evaluation in 2005 of substances known as antioxydants, vitamin A, vitamin C, vitamin E, carotene, selenium failed to establish that they had a preventive effect against various diseases. A new review of 68 trials testing the preventive effects of antioxydants against various diseases shows that the death rate was not influenced by antioxydants. A review of 47 high- quality trials involving more than 180,000 participants shows a higher death rate in the groups treated with vitamins A and E and beta-carotene. Another analysis based on more than 150,000 people showed no difference between antioxydants and placebo in preventing macular degeneration (disease of the eye). A trial on prevention of type 2 diabetes compared selenium treatment with a placebo in more than 1200 people. After monitoring for an average of 7.7 years, the incidence of diabetes was 12.6 cases per 1000 people a year in patients receiving selenium, compared with 8.4 cases in those taking the placebo. Overall, numerous trials evaluating antioxydants show that their preventive effect is hypothetical; there is even evidence of a higher death rate and higher morbidity with some antioxydants.

©Prescrire June 2008

Reference: "Antioxydants : pas en prévention (suite)" Rev Prescrire 2008 ; 28 (296): 455-456.

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