High doses of vitamin E may increase a man's risk for prostate cancer, according to a study published Tuesday by the Journal of the American Medical Association.
Researchers at the Cleveland Clinic created the SELECT trial in 2001 to investigate the protective benefits of both selenium and vitamin E for prostate cancer prevention, but found just the opposite: Vitamin E, specifically, caused a significant increase in prostate cancer risk in the study group, while selenium showed no added risk, but also no benefit.
"These were surprising findings in view of all the data that suggested they were beneficial," said Dr. Eric Klein, chairmain of Urology at the Cleveland Clinic and the lead author of the study. And, he said, the numbers were equally surprising.
"For every 1,000 men who took a placebo, there were only 65 new cancers," he said. "For every 1,000 men who took vitamin E, 76 got prostate cancer. That's a statistically significant increase."
A 17% increase in fact - too high to attribute the additional cases merely to chance, he said.
Based on the results of this trial, Klein suggested that men should have a serious conversation with their doctors about whether taking vitamin E supplements is a good idea.
"About half the men who are age 60 or older take vitamin E, and about a quarter take vitamin E at the level that was used in [the trial]: 400 international units or more," he said. "In my opinion, there is no compelling evidence that vitamins are beneficial, and there is some evidence that they can be harmful."
Klein said many multivitamins contain much smaller amounts of vitamin E – around 15 IU – slightly less than the 22 IU of vitamin E per day recommended by the Institute of Medicine. The people in the study were getting 18 times what is recommended daily. Klein said it's unclear what effect vitamin E at low doses may have on prostate cancer risk.
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