Adding to the evidence that regularly taking dietary supplements may do more harm than good, researchers at the Cleveland Clinic have found that men taking vitamin E are not protected from prostate cancer, and may even be at higher risk for disease, compared with men not using the supplements.
The new study is only the latest blow to E, a popular supplement that has been touted as a powerful way to prevent everything from prostate and breast cancer to heart disease, vision loss and Alzheimer's. In recent years, however, in-depth studies have broken vitamin E's healthy spell, finding that people who take it are no better off than people who don't.
Still, based on animal studies and early population studies, scientists had believe that vitamin E supplementation could be a smart and inexpensive way to prevent prostate tumors, given that the vitamin's antioxidant effects may combat potentially damaging changes to the DNA in prostate cells.
"This finding was surprising, because all the evidence previously suggested that vitamin E may be protective against prostate cancer," says the Cleveland Clinic's Dr. Eric Klein, lead author of the new study published in the Journal of the American Medical Association.
The current study is a follow-up to one of the first rigorous studies of the effects of vitamin E and selenium on prostate cancer risk, published by Klein and colleagues in 2008. That study, in which men were randomly assigned to take either supplement, or both together, or a placebo, Klein and his team found no difference in cancer risk among any of the groups, suggesting that vitamin E offered no protective anticancer benefit. Based on those results, the study was stopped. Additional analysis revealed that vitamin E may even boost risk of developing tumors.
So, it's still possible that vitamin E supplements may help prevent some disease. So far, the most promising results are with Alzheimer's patients. In some studies, people with early signs of dementia show slower rates of cognitive decline if they take vitamin E than if they don't. But even here, the evidence isn't strong enough for doctors to recommend that those on the road to Alzheimer's take E to ward off their disease.
Overall, it seems, the growing consensus is that unless you need supplements to treat a specific deficiency, nutrients and vitamins are best obtained through a healthy diet. And that goes for E as well, says Klein, since it won't help you avoid cancer. "There doesn't seem to be much benefit to taking vitamin E if you are otherwise healthy," says Klein.