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Today in Your Health, we'll ask if dietary supplements and healthy food are really so healthy. In a moment we'll pose that question for gluten-free food. First, consider the vitamins that may be on your kitchen counter or in your medicine cabinet. People have been buying more of those and other dietary supplements, which many scientists think most people do not need. Turns out, they can even do harm, as NPR's Richard Knox reports.
RICHARD KNOX, BYLINE: Lee Robinson, a real estate broker in Boston, is opening her well-stocked medicine cabinet.
LEE ROBINSON: Daily multiple vitamin for women and it's got everything under the sun in it.
KNOX: She says her doctor advises her to take several dietary supplements.
L. ROBINSON: First thing in the morning, brush your teeth, take your vitamins.
KNOX: Her husband Paul says his doctors have also told him to take supplements.
PAUL ROBINSON: I get tired in the afternoon. And they believe that if I take a senior multivitamin, I'm going to feel better.
KNOX: The Robinsons have lots of company. Consider this statistic: Eighty-five percent of older women in Iowa use a daily supplement. That's according to one new study, which looked at nearly 39,000 older women over almost 20 years. Over that time they found an astounding increase in their use of supplements.
And they found something else. Those who took supplements did not live longer. In fact, they died earlier - three to 10 percent earlier, depending on which vitamins and minerals they were taking. Jaakko Mursu of the University of Minnesota is the study's lead author.
JAAKKO MURSU: I would advise people to reconsider their supplement use. And I would hope that they would pay more attention to the diet.
KNOX: Now, Mursu says the research doesn't prove that supplements are dangerous. The mortality increase was too small and there are too many other factors to consider. But the study certainly didn't show that supplements are doing any good either. Dr. Rita Redberg is editor of the Archives of Internal Medicine, which published that study. When it comes to dietary supplements, she doesn't mince words.
DR. RITA REDBERG: There's no reason to be taking multivitamins. These vitamins have no benefit to health.
KNOX: She says people think that if a little bit of a nutrient is good, more is better. And that's a fallacy. Scientists have often been disappointed when they've looked at whether things like beta-carotene, vitamin E, vitamin C and other nutrients can prevent cancer, heart disease, Alzheimer's and other diseases. Redberg says very few people need dietary supplements.
REDBERG: Perhaps if someone had a documented nutritional deficiency or a disease related to a nutritional deficiency. Those are pretty rare in this country.
KNOX: And some studies have actually shown an increase in disease. One of these is in the current issue of the Journal of the American Medical Association. Researchers asked 36,000 men to take vitamin E or a mineral called selenium. The hope was that one or both would help prevent prostate cancer.
But neither did, alone or together. In fact, men who took vitamin E had a 17 percent higher risk of prostate cancer. Dr. Ian Thompson at the University of Texas helped lead that hundred-million-dollar study.
DR. IAN THOMPSON: The take-home message for this is that a man who is taking vitamin E, that man should probably stop taking it. And by doing so, he may reduce his risk of prostate cancer.
KNOX: Proponents of dietary supplements say studies like these are flawed because they look at vitamins and minerals as though they were drugs.
TAYLOR WALLACE: They're not drugs.
KNOX: That's Taylor Wallace of the Council for Responsible Nutrition, which represents the makers of dietary supplements.
WALLACE: They're not meant to treat a disease. They're meant to help to maintain a healthy lifestyle.
KNOX: That's a slippery concept, hard to nail down scientifically. But it's one that apparently a lot of consumers buy into. And so do their doctors. Andrea Ayvasian, a 60-year-old Massachusetts woman, heard that last week from her doctor.
ANDREA AYVASIAN: She said your cholesterol is enviable. You're disciplined about your exercise routine. You're in the right weight range. You're healthy, my dear.
KNOX: Then Ayvasian pulled out a bunch of dietary supplements and asked if she should keep taking them.
AYVASIAN: And she looked at each jar and said yes, yes, yes, yes to each one.
KNOX: Now Ayvasian is having second thoughts. She says she's going to call up her doctor and ask, do I really need these?
Richard Knox, NPR News, Boston. Transcript provided by NPR, Copyright NPR.