By Rob Stein
Washington Post Staff Writer
Tuesday, October 28, 2008
A large government study of whether Vitamin E and selenium protect men against prostate cancer has been suspended, federal health officials announced yesterday, after an independent analysis determined that the nutrients did not reduce the risk for the common malignancy.
The $119 million study, involving more than 35,000 men, also found hints that the nutrients might increase the risk for prostate cancer and diabetes, although officials stressed that those findings may be a coincidence.
Nevertheless, the study's organizers had begun notifying participants to stop taking the pills they were receiving, and offered to tell them whether they were taking the nutrients or placebos. All the participants will continue to have their health monitored for about three years.
The announcement marks the latest in a series of disappointing findings about the potential health benefits of vitamins and other nutritional supplements, which earlier studies had indicated could have a host of advantages. One theory was that antioxidants could mop up damaging free radicals, which are a natural byproduct of cellular processes in the body.
But subsequent studies testing antioxidants and other nutritional supplements have not confirmed the benefits, and several have even been alarming. For example, beta carotene increased, rather than decreased, the risk of lung cancer among smokers, and Vitamin E -- also touted as helping to prevent heart disease -- appeared to boost the overall risk.
The new study was funded by the National Institutes of Health after earlier studies indicated the nutrients may protect against prostate cancer, the most common cancer in men after skin cancer. Men age 50 and older received one or both of the nutrients or placebos at 400 sites in the United States, Puerto Rico and Canada.
An independent panel of experts monitoring the study discovered, after men had been taking the supplements for about five years, that there was no benefit but that there were suggestions of possible harm, prompting officials to stop the project.
"The important message for consumers is that taking supplements, whether antioxidants or others, is not necessarily beneficial and could be harmful," said Eric Klein of the Cleveland Clinic, a study coordinator. "You should not be taking them unless there is a rigorous scientific study that shows a benefit."
Andrew Shao of the Council for Responsible Nutrition, an industry group, said in a statement that the findings did not "discount the value of taking vitamin E and selenium for other general benefits."