Survey of studies finds that some supplements increase the risk of mortality
A damning report published this week in the Journal of the American Medical Association (JAMA) has added fuel to the health controversy surrounding antioxidant supplements, concluding that some of them increase the risk of death.
Goran Bjelakovic from Copenhagen University Hospital in Denmark and his colleagues analysed previous studies examining the effects of antioxidant supplements. They found that beta carotene and vitamins A and E, given singly or combined with other antioxidant supplements, ’significantly increased mortality’.
The study was a meta-analysis of 68 trials involving over 230,000 participants. Trials were put into ’low quality’ and ’high quality’ categories according to their methodology.
An analysis of all of these trials showed no significant association between antioxidant use and mortality. However, when only the 47 high quality trials, said to have a low bias risk, were analysed, the results were very different.
’Our findings contradict observational studies, claiming that antioxidants improve health,’ the authors reported, adding that, their results showed vitamin C to have no beneficial or negative effect on health.
Selenium was the only supplement to show health-promoting effects, although the study’s authors were not convinced of its benefits, writing that ’more research was needed on this question’.
G Bjelakovic et al, JAMA, 2007, 297, 842