The largest analysis of data on antioxidant vitamins ever conducted has shown that beta-carotene, vitamin A, and vitamin E probably increase mortality. Two other antioxidant substances — vitamin C and selenium — had no effect on mortality.

meta-analysis of 68 randomized trials with a total of 232,606 participants, published in the February 28 issue of JAMA, was conducted by a group led by Goran Bjelakovic, MD, of the Copenhagen University Hospital in Denmark

many people are taking antioxidant supplements in the belief that they improve health and prevent diseases. Many primary or secondary prevention trials of antioxidant supplements have been conducted to prevent several diseases — mainly cardiovascular disease and cancer — but results have generally not been positive, with some trials showing increases in mortality.

"We don't know exactly how they are doing harm but rather than preventing cardiovascular disease and cancer, they actually seem to be accelerating these conditions."