Studies have been showing that vitamins are linked to cancers. 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.
The SELECT trial, which was funded by the National Cancer Institute, involved 35,000 men and tested one or both supplements, or a placebo. By 2008, the study was halted when no benefit was seen.
These were surprising findings in view of all the data that suggested they were beneficial,” said Dr. Eric Klein, chairman 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.
“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. Klein said it’s unclear what effect vitamin E at low doses may have on prostate cancer risk. 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.