It’s only Tuesday, but so far it’s shaping up to be a pretty lousy week for the promise of dietary supplements to prevent serious diseases.
On Monday, as the WSJ reports, the Archives of Internal Medicine published a study showing a small increased risk of death among older women who took vitamins and other supplements.
And today the Journal of the American Medical Association published an update to a trial that looked at whether selenium and vitamin E could prevent prostate cancer … and found that the men who took vitamin E actually had a 17% higher risk of the disease than men who took a placebo. Selenium didn’t seem to have any effect at all, good or bad. Here’s the WSJ story.
That study, called Select, was launched in 2001 because animal studies, observational studies of humans, and secondary findings from trials suggested a protective effect. But giving supplements of the nutrient in relatively large quantities — the study dosed men with 400 IU of vitamin E, more than the 22.4-IU recommended dietary allowance — in a randomized, controlled trial didn’t show a benefit.
Now, of course, the question is why. More research is necessary to pin down the biology of how nutrients affect cells at different stages — as they move from normal to abnormal to cancerous, says Lori Minasian, a co-author of the study and acting director of the National Cancer Institute’s Division of Cancer Prevention.
Efforts to single out nutrients found in a healthful diet and to give them in supplement form in the attempt to stave off cancer (and other diseases) have largely fallen flat. That’s not surprising, given the complexity of cancer and how long it can take to develop, says Andrew Vickers, a prostate-cancer researcher at Memorial Sloan-Kettering Cancer Center.
And foods, too, are complex, he says. Almonds, for example, may have vitamin E, but they also contain a host of other substances and chemicals that likely work together to bring any beneficial effects. Or, eating nuts may take the place of other foods that may have harmful effects.
For now, unless there’s a medical reason to do otherwise, the best advice is to get those nutrients in their original form — in foods, as part of a healthful diet — rather than trying to take them as supplements, experts say.
(Duffy MacKay, vice president of scientific and regulatory affairs at the Council for Responsible Nutrition, which represents supplement makers, told the WSJ yesterday it’s tough for most people to get all their nutrients from food, and that vitamin supplements can fill in important gaps in nutrition.)
The latest study “should be a caution for men to think about what they’re doing,” says Laura Crocitto, clinical associate professor of surgery, urology and urologic oncology at City of Hope in Duarte, Calif. She recommends men talk to their physicians about taking supplements and try to participate in trials rather than self-treat.