Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases

Many people take antioxidants in the belief that they will prolong their life expectancy. However, data from 67 randomised trials that involved just under a quarter of a million people failed to support this idea, a Cochrane Systematic Review has discovered.

"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," says Goran Bjelakovic, visiting researcher, who performed the systematic review at the Copenhagen Trial Unit at the Copenhagen University Hospital in Denmark.

The idea that antioxidants can extend life comes from human and animal laboratory research and has been boosted by some observational clinical studies. But other studies have indicated neutral or even harmful effects.

Cochrane reviews are based on peer reviewed published protocols that aim to identify randomised, published and unpublished, trials. Following Cochrane methodology, relevant data are extracted and pooled together from the identified trials, which are also assessed and subdivided into unbiased and biased in terms of methodology of their conductance, so that unbiased assessments of intervention effects can be conducted.

"The findings of our review show that if anything, people in trial groups given the antioxidants 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. So regarding these antioxidants we need more data from randomised trials," says Bjelakovic. "The bottom line is that current evidence does not support the use of antioxidant supplements in the general healthy population or in patients with certain diseases."