WebMD Medical News
Brenda Goodman, MA
Brunilda Nazario, MD
Feb. 27, 2013 -- For years, women have been told to take extra calcium to guard against osteoporosis.
But doctors just reversed that advice. After looking at scores of studies, the U.S. Preventive Services Task Force (USPSTF) says that common doses of calcium and vitamin D don’t prevent fractures in women past menopause who have healthy bones, and they may raise the risk of kidney stones.
That recommendation comes on the heels of two new studies showing that men and women with high calcium levels from supplements were more likely to die of heart disease than those who got less calcium or who got their calcium from diet alone.
Calcium is just the latest supplement to falter under scientific scrutiny. Other studies have questioned the value of fish oil, and antioxidants like vitamins C, E, and beta-carotene.
Does that mean you should ditch your daily calcium pill? What about other kinds of supplements?
Experts on both sides of the debate say that despite discouraging headlines, it’s still smart for some people to take supplements, depending on their individual nutritional needs.
“I think scientists are still trying to make sense of it all, particularly the latest calcium studies. In many cases the risks don’t appear to apply to all people,” says Carol Haggans, a registered dietitian who keeps up with the latest research for the Office of Dietary Supplements at the National Institutes of Health.
Duffy MacKay, ND, cautions that nutrition research is complex and still “in its infancy.” He is vice president of scientific and regulatory affairs at the Council for Responsible Nutrition, a group that promotes supplements.
Haggans says people should get two messages loud and clear:
Here’s what science says about several other popular supplements:
Women planning a pregnancy need at least 400 micrograms of folic acid from fortified foods or supplements each day, according to the National Institute of Medicine. Folic acid has been shown to prevent serious birth defects of the spine and brain. It may also cut a child’s chances of developing autism.
A recent study in the Journal of the American Medical Association found that women who started taking folic acid at least a month before their pregnancy and for eight weeks after conception had a 40% lower risk of having a child with autism than women who didn’t take folic acid.
The body turns beta-carotene into the antioxidant vitamin A.
Foods rich in beta-carotene, such as leafy greens and orange and yellow vegetables, lower the risks for cancer and heart disease. But studies show beta-carotene supplements don’t lessen cancer or heart disease risks in healthy adults and may raise the risk of lung cancer in smokers and people exposed to asbestos.
Vitamin B12 helps the body make red blood cells. It also aids nerve and brain function.
B12 is bound to the protein in animal products. Younger adults usually get plenty of this key nutrient by eating meat, poultry, fish, eggs, milk, and fortified cereals.
Older adults lose the ability to separate B12 from protein, which can cause a deficiency. The Institute of Medicine recommends that adults over age 50 take B12 supplements, which are easier to absorb. Vegetarians who don’t eat breakfast cereals may also need supplements.
Studies have found that eating fish rich in omega-3 fatty acids lowers the risk of heart attacks and strokes, but the evidence supporting the use of fish oil supplements is mixed.
A large research review published last year in the Journal of the American Medical Association found that people taking fish oil pills didn’t have lower rates of heart attacks, strokes, or deaths compared to those who took placebo pills. According to the researchers, while many of these large studies have limitations, the results did not seem to justify the use of omega-3 supplements as an intervention for heart disease prevention in some people.
Why might eating fish be better than taking fish oil? Experts say that like all whole foods, fish are complex mixtures of vital nutrients. It could be that all those nutrients work together to provide the benefit. Or it may be that fish replaces less healthy sources of protein in the diet, like red meat.
Until more is known, experts say there doesn’t seem to be any harm in taking fish oil, as long as you don’t mind spending the money.
Doctors had high hopes that vitamin E might prevent cancer and heart disease, but the best studies of vitamin E have failed to show benefits from taking supplements. Instead, some studies have suggested that taking large doses of vitamin E might be risky.
One large trial randomly assigned more than 35,000 men to take vitamin E, selenium, both supplements, or a placebo pill. After seven years, doctors found that men who took vitamin E were about 17% more likely to develop prostate cancer compared to those taking the placebo.
Another study that randomly assigned 10,000 men and women at high risk for heart disease to take either vitamin E or a placebo daily for almost five years found no differences in the numbers of deaths, heart attacks, or strokes between the groups.
While a few small studies have shown that C may shorten the length of a cold, the vast majority have found no effect of the vitamin on preventing or shortening colds. In addition, a recent large study of nearly 49,000 Swedish men found those who took about 1,000 milligrams of vitamin C supplements a day were about twice as likely as those who didn’t take supplements to develop kidney stones 11 years later.
Milk, whether it’s cow’s milk or fortified soy or almond milk, is one of the best sources of calcium in the diet, and Americans don’t drink enough of it, according to the USDA. As a result, calcium and vitamin D were listed as a “shortfall nutrients” in the latest dietary guidelines.
Many adults turn to calcium and vitamin D supplements to bridge the gap. But evidence suggests supplements may not be as effective.
According to the new recommendation from the USPSTF, supplements of up to 1,000 milligrams of calcium and 400 IU of vitamin D don’t prevent fractures in postmenopausal women with healthy bones.
The new recommendations don’t apply to the estimated 30% of postmenopausal women who have osteoporosis. And they don’t apply to women who have low vitamin D levels or those who are at high risk for falls. The panel also said there wasn’t enough evidence to say whether supplements might help men or younger women.
At the same time, new studies have questioned the safety of calcium supplements. Early research suggests that people who take calcium supplements have a higher risk for heart disease than those who do not take the supplements.
Until more is known, food is probably the best way to meet your daily calcium needs, which range from 1,000 to 1,200 milligrams for adults.
Aim for three dairy servings a day, from milk, yogurt, or low-fat cheese. Or look for fortified foods like cereals and juices.
SOURCES:Duffy MacKay, ND, vice president of scientific and regulatory affairs, The Council for Responsible Nutrition, Washington, D.C.Carol Haggans, RD, consultant, Office of Dietary Supplements, National Institutes of Health, Bethesda, Md.U.S. Preventive Services Task Force: "Calcium and Vitamin D to Prevent Fractures, Final Recommendation."Xiao, Q. Jama Internal Medicine, Feb. 4, 2013.Michaelsson, K. BMJ, Feb. 12, 2013.Institute of Medicine: “Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.”Suren, P. JAMA, Feb. 13, 2013.Takata, Y. Nutrition and Cancer, January 2013.Voutilainen, S. American Journal of Clinical Nutrition, 2006.USDA, Dietary Guidelines for Americans, 2010.Office of Dietary Supplements: "B-12 Fact Sheet for Health Professionals."Chowdhury, R. BMJ, Oct. 30, 2012.Rizos, E. JAMA, Sept. 12, 2012.Sydenham, E. Cochrane Database of Systematic Reviews, June 13, 2012.Dunn, BK. Nutrition and Cancer, 2010.Yusuf, S. The New England Journal of Medicine, Jan. 20, 2000.Thomas, L. JAMA Internal Medicine, February 4, 2013.Office of Dietary Supplements: "Calcium Fact Sheet."
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