April 16, 2008
LONDON, England (CNN) -- Taking antioxidants like vitamins A and E to prolong life may actually have the opposite effect, new research has found.
A review of 67 studies involving more than 230,000 people found "no convincing evidence" that the vitamins prolonged life, the Press Association reported.
"Even more, beta-carotene, vitamin A, and vitamin E seem to increase mortality," according to the researchers.
However, other health specialists said the research was "flawed" and the supplements were safe to take.
The review, published by The Cochrane Collaboration, involved trials on beta-carotene, vitamin A, vitamin C, vitamin E, and selenium.
The experts said the studies involved different doses of each antioxidant. A total of 232,550 people were involved.
Forty-seven trials included 180,938 people and had a low risk of bias. In these trials with a low risk of bias, the "antioxidant supplements significantly increased mortality", the report's authors wrote.
When the different antioxidants were assessed separately and low risk of bias trials were included and selenium excluded, vitamin A was linked to a 16% increased risk of dying, beta-carotene to a seven percent increased risk and vitamin E to a four percent increased risk.
However, there was no significant detrimental effect caused by vitamin C, the authors said.
"We found no evidence to support antioxidant supplements for primary or secondary prevention," they added. "Beta-carotene, vitamin A and vitamin E given singly or combined with other antioxidant supplements significantly increase mortality."
There was no evidence vitamin C increased longevity.
"Selenium tended to reduce mortality but only when high-bias risk trials were considered. Accordingly, we need more research on vitamin C and selenium."
Goran Bjelakovic, a visiting researcher who carried out the review at Copenhagen University Hospital in Denmark, told the Press Association: "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.
"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."
Patrick Holford, a nutritionist who has formulated some supplements for the firm Biocare, told the Press Association that the Cochrane review was a "stitch up."
"Antioxidants are not meant to be magic bullets and should not be expected to undo a lifetime of unhealthy habits," Holford said.
"But when used properly, in combination with eating a healthy diet full of fruit and vegetables, getting plenty of exercise and not smoking, antioxidant supplements can play an important role in maintaining and promoting overall health."
Dr Michele Sadler, of the Health Food Manufacturers' Association, said the analysis was "flawed."
"Healthy consumers can still feel confident that they can safely take their antioxidant supplements."
http://www.cnn.com/2008/HEALTH/diet.fitness/04/16/vitamins.health/index.html
