Bjelakovic G, Nikolova D, Gluud LL et al. JAMA 2007; 297: 842-57.
Fears regarding the use of HRT have led to the increasing popularity of antioxidant supplements. It has been estimated that 10-20 per cent of the adult population (80-160 million people) in the US and Europe may take antioxidants, prompted by claims that they improve health.
This meta-analysis examined 68 randomised trials with 232,606 participants (385 publications). The trials involved adults and compared beta carotene, vitamin A, vitamin C (ascorbic acid), vitamin E and selenium, singly or in combination, versus placebo or no intervention.
The dose and regimen of the antioxidant supplements were: beta carotene 1.2-50.0mg (mean 17.8mg), vitamin A 1,333-200,000IU (mean 20,219IU), vitamin C 60-2,000mg (mean 488mg), vitamin E 10-5,000IU (mean 569IU) and selenium 20-200eg (mean 99eg) daily or on alternate days.
Mean duration of follow-up was 3.3 years (range 28 days to 14.1 years).
The mean age was 62 years (range 18-103 years). The mean proportion of women was 44.5 per cent in the 63 trials reporting gender. Beta carotene, vitamin A and vitamin E intake appeared to increase mortality, but vitamin C and selenium appeared to have no significant effect. So there was no convincing evidence that antioxidant supplements have beneficial effects on mortality.
However, these findings with synthetic antioxidants should not be translated to potential effects of fruit and vegetables, which contain other substances, such as fibre. Increased intake of vegetables, as in the Mediterranean diet, appears to be associated with reduced mortality.
- Miss Margaret Rees is reader in reproductive medicine and honorary consultant in medical gynaecology at John Radcliffe Hospital, Oxford