By Kathleen Doheny
WebMD Health News
Reviewed by Michael W. Smith, MD
A national task force that's been studying the issue for 2 years says there is not enough evidence to show they help. In most cases, they won't do any harm, either.
But the conclusions suggest that those counting on vitamins and supplements to ward off cancer or heart disease are wasting their money.
It's a giant amount of money, too. In the U.S., the supplement industry has grown to $28 billion a year. About a third of U.S. adults say they take a multivitamin or mineral supplement, and half use at least one dietary supplement.
The new recommendations are published today in the Annals of Internal Medicine. A draft version was released in November 2013.
There's been a steady stream of similar recommendations from other well-known organizations, such as the National Institutes of Health, the Academy of Nutrition and Dietetics, the American Cancer Society, the American Heart Association, the American Academy of Family Physicians, and other groups.
Today's recommendations come from the U.S. Preventive Services Task Force, which weighs the latest data on how to prevent disease. It released a draft version in November 2013. The research includes 28 studies.
An industry group notes that the task force focused only on heart disease and cancer. There are ''no recommendations on the value of vitamins and minerals for overall health and wellness, or for filling nutrition gaps, the areas for which research tells us consumers are most likely to take them," says Duffy MacKay, ND, of the Council for Responsible Nutrition. The council calls for more research.
WebMD asked Michael LeFevre, MD, co-chair of the task force, for his comments. LeFevre is professor and vice chair of family and community medicine at the University of Missouri.
What did the task force find about the use of vitamins and supplements to prevent heart disease and cancer in healthy adults?
"With two exceptions, at this point we found the science is not sufficient to show either how much harm or benefit there is for taking multivitamins to prevent cancer or heart disease. The two exceptions are vitamin E and beta-carotene, which we are recommending against."
"We are moderately certain they are not of benefit," LeFevre says.
"For people at high risk of lung cancer, such as smokers, there is actually a higher risk of lung cancer with using beta-carotene. Our recommendations on vitamin E and beta-carotene apply to everyone, however."
Does the task force recommend any vitamins or supplements to prevent cancer and heart disease?
"The task force does not. The task force says the science is insufficient to make a recommendation one way or the other. However, we are not recommending against supplements. It's true we didn't find benefit. It's also true we didn't find enough evidence to be certain about benefit or harm, with the two exceptions.
"My personal take, in my day job as a family physician, is that nutrition is important in both cancer and heart disease prevention. Eating a diet rich in fruits, vegetables, whole grains, fat-free and low-fat dairy foods, and seafood has been associated with a decrease in cardiovascular disease and cancer."
The disease-fighting elements in a good diet are:
- Fiber, which aids weight control and lowers heart and cancer risks
- Antioxidants, which fight disease-causing cell damage
- Omega-3 fatty acids, which lower blood pressure among other benefits
Talk with your doctor about vitamin use, LeFevre says. "In my practice, for example, before recommending a supplement I would want to see evidence that benefits outweigh harms."
What about task force recommendations on vitamins and supplements for other purposes?
"We have a positive recommendation for vitamin D in frail elderly patients at risk for falling. We have a negative recommendation for calcium and vitamin D in postmenopausal women at the usual dose -- 1,000 milligrams of calcium and 800 milligams of vitamin D, [because it] does not reduce fracture risk -- the outcome we looked at."
Will you revisit the issue of vitamins for heart disease and cancer prevention?
"We typically revisit an issue every 5 years. We sometimes will update a recommendation earlier if we become aware of additional studies."
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SOURCES: Michael LeFevre, MD, co-vice-chair, U.S. Preventive Services Task Force; professor and vice chair, family and community medicine, University of Missouri, Columbia. U.S. Preventive Services Task Force, Annals of Internal Medicine, Feb. 24, 2014. Statement, Council for Responsible Nutrition, Feb. 24, 2014.
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