The three supplements are marketed on the premise they deliver antioxidants to the body to mop up free radicals, thought to be responsible for some of the effects of ageing. But none was found to lengthen the lives of those who took them, according to an analysis in the Journal of the American Medical Association of all the substantial trials done to date.
Scientists of the respected Cochrane collaboration, which regularly pools data from trials to evaluate drugs and medical treatments, discovered the three supplements had the opposite effect. Those who took them, in 47 trials with 180,938 people, had a 5% greater risk of dying than those who did not.
Other common supplements with similar claims made for them, vitamin C and selenium, did not increase risk of death, the researchers from Copenhagen University hospital in Denmark found, but only selenium may have some benefit. "Our systematic review contains a number of findings. Beta carotene, vitamin A, and vitamin E given singly or combined with other antioxidant supplements significantly increase mortality," wrote Goran Bjelakovic and colleagues.
"There is no evidence that vitamin C may increase longevity. We lack evidence to refute a potential negative effect of vitamin C on survival. Selenium tended to reduce mortality, but we need more research on this question." Around 10% to 20% of people in Europe and North America take these supplements regularly, so "the public health consequences may be substantial", they say. People are exposed to "intense marketing" they add, but consumers would be better obtaining antioxidants from fruit and vegetables.
But Balz Frei, director of the Linus Pauling Institute at Oregon State University, said the study and the data were flawed, because more than two-thirds of research examined used people with heart disease, cancer, or other risks, treated to see if the supplements worked: "Over the years it has become clear ... antioxidants don't work in disease treatment."
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