Daily use of vitamin E increased the risk of prostate cancer in healthy men, according to the latest study to find potential harm associated with regular use of some dietary supplements.
Men who took vitamin E over a seven-year period were 17 percent more likely to get prostate cancer than those who took a placebo, according to the research published in the Journal of the American Medical Association. The study, a follow-up to a 2008 trial of 35,000 men designed to see if the supplements helped prevent prostate cancer, was halted at the time when results showed no benefit.
The findings add to a growing body of research that suggests some vitamins and supplements, used regularly by an estimated 234 million U.S. adults, may do more harm than good. A study published yesterday in Archives of Internal Medicine concluded that the use of multivitamins and supplements including folic acid, iron, magnesium and copper were associated with higher death rates among older women.
“There is no reason for men in the general population to take the dose of vitamin E,” said Eric Klein, a co-chair on the study and a physician at the Cleveland Clinic, in a statement. “The supplements have shown no benefit and some very real risks.”
The study, dubbed SELECT for Selenium and Vitamin E Cancer Prevention Trial, was designed to see if one or both of the substances prevent prostate cancer. Last May, the data and safety monitoring committee reviewed the trial data and recommended reporting the finding of the prostate cancer risk, researchers said in the study.
The latest data, which continue to track the men in the study, showed those who took 400 international units of vitamin E daily had a cancer rate of 76 cases per 1,000 participants, compared with 65 cases in the placebo group.
The 17 percent increased risk was found in the group of study participants that took vitamin E alone. Those who took a combination of vitamin E and selenium did not have a significant increase in risk, according to the study.
The study “is the largest, the most definitive, and the first one to show that there could potentially be harm,” from regular use of vitamin E, said Leslie Ford, associate director for clinical research at the National Cancer Institute’s cancer prevention division, in an interview.
The study was funded by the National Cancer Institute and the National Institutes of Health.
Vitamin E Function
Claims about vitamin E’s health benefits stem from its function as an antioxidant that prevents the breakdown of other molecules in the body and, if unchecked, could lead to cancer. It also strengthens the immune system, according to the National Institutes of Health. It’s naturally found in wheat germ oil, sunflower seeds, spinach and broccoli.
Earlier studies in the 1990s looking at other types of cancer showed men who took the vitamin were less likely to be affected by prostate cancer. More recently, a 2005 study published in the Journal of the American Medical Association concluded that the supplement failed to prevent cancer or heart disease.
Prostate cancer is the second-leading cause of cancer death in men, according to the American Cancer Society. More than 240,000 men will be diagnosed with the disease this year, and it will lead to about 33,730 deaths, the organization said.
“The observed 17 percent increase in prostate cancer incidence demonstrates the potential for seemingly innocuous yet biologically active substances such as vitamins to cause harm,” the researchers said in the study. The findings “underscore the need for consumers to be skeptical of health claims for unregulated over-the-counter products in the absence of strong evidence of benefit demonstrated in clinical trials.”
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