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Doubts About Calcium

By January W. Payne
Washington Post Staff Writer
Tuesday, February 28, 2006

Calcium and vitamin D supplements -- long recommended for post-menopausal women as a way to protect their bones -- were found not to reduce the risk of hip fractures in a large, closely watched study published this month. This has left some women confused about the value of taking the pills.

The Women's Health Initiative (WHI), a 15-year federally funded study involving more than 36,000 women ages 50 to 79, found that taking calcium (1,000 milligrams daily) and vitamin D (400 international units daily) improved hip bone density, but didn't decrease the risk of hip fractures. (See Quick Study, Page F6.) While the findings may influence the direction of future studies, researchers admit they offer limited practical guidance for physicians and patients.

How should women respond meanwhile? We put that question -- and others -- to experts last week.

Am I the only one confused by the new findings?

Hardly. The study has "generated a lot of questions from patients," said Ethel Sirus, director of the Toni Stabile Osteoporosis Center at the New York-Presbyterian Hospital and president of the National Osteoporosis Foundation. But she and other experts said they don't expect the findings to change doctors' advice that patients get calcium and vitamin D through diet, sun exposure and, if necessary, through supplements.

Wait a minute. Didn't the study find there's no value in taking calcium supplements?

That's an overstatement. As far as bone health -- the primary focus of the study -- goes, there are still too many unknowns to reach a solid conclusion. A subgroup of older women -- age 60 and over -- who took the supplements did show some reduction of hip fracture risk, but benefits in the overall group were not statistically significant. On colorectal cancer -- a secondary focus -- the supplements also appeared to offer no benefit. The study didn't look at other possible benefits of calcium supplementation including cardiovascular health.

Weren't there some caveats?

There were, and that's why many doctors aren't telling patients to stop taking their calcium and vitamin D supplements. Not all study participants took the supplements as directed. Some began taking prescription medications to ward off bone thinning. And some women in the placebo group took supplements on their own, making it harder to discern differences between the intervention group and the placebo group.

Researchers have also raised questions as to whether the vitamin D dose was high enough or the study large enough to detect differences in fracture risk .

Why do doctors recommend women take calcium supplements as they approach menopause?

The idea is to protect bones against age-related thinning thought to make them more susceptible to fracture. Calcium is the "most abundant mineral in the human body," according to the federal Office of Dietary Supplements (ODS), and more than 99 percent of it is stored in the bones and the teeth.

"Bone undergoes continuous remodeling," the ODS explains, with constant bone breakdown and formation, which involves the depositing of calcium into the newly formed bone. With age, says the ODS, eventually "bone breakdown exceeds formation, resulting in bone loss, which increases the risk for osteoporosis," a condition that increases the risk of fractures.

Vitamin D, whether from food, sunlight or as a supplement, is recommended to promote the absorption of calcium.

This isn't the first study to cast doubt on the value of taking calcium supplements, is it?

Previous findings have been mixed, said Joan McGowan, a project officer for the WHI study and director of the musculoskeletal diseases branch at the National Institute of Arthritis and Musculoskeletal and Skin Diseases. A few recent studies have shown little bone benefit from calcium supplementation, experts said; getting some participants to take their supplements as directed was a problem, just as it was in the WHI study. But in another bone study involving frail older women, calcium supplementation appeared beneficial. Researchers say additional study is needed to provide more conclusive results.

How could calcium be shown to increase bone density but not decrease fracture risk? Aren't the two tied?

Not necessarily. "Low bone density is only one of the risk factors for fracture," McGowan said in an e-mail interview. Other factors include age, genetics and propensity to fall ,she said.

How reliable are bone density tests in assessing my risk of future fractures?

The Mayo Clinic calls the tests a "fairly accurate predictor of your risk of fractures" and a "valuable tool in the diagnosis of osteoporosis." Some studies have cast doubt on the tests' ability to predict fractures, but for now they are the best tool available.

So, how much calcium and vitamin D am I supposed to get every day?

The Institute of Medicine recommends adults ages 51 and over take in about 1,200 milligrams of calcium per day. Recommended intake for vitamin D is 10 micrograms (400 international units) for adults ages 51 to 70, and 15 micrograms (600 international units) for those ages 71 and over.

Experts also recommend regular weight-bearing exercise to maintain bone density. Most experts recommend that women 65 and older, and younger women at increased risk for osteoporosis, have regular bone density tests. Patients at increased risk may be advised to take medications, such as bisphosphonates, if necessary.

I read that women who took supplements in the study were more likely to have kidney stones. Do the benefits of calcium supplements outweigh the risk?

"We certainly don't want to be in a position to trade one benefit for the risk of painful kidney stones," said McGowan. Still, she said, "there certainly is a lot more pain and suffering and disability and even death associated with hip fractures."

The kidney stone link also needs to be explored further, McGowan said, especially since earlier studies showed that increasing dietary calcium -- that is, the calcium you get through food and fluids -- was protective against kidney stones, while taking a calcium supplement did not offer a similar benefit.

Can I get all the calcium and vitamin D I need from my diet alone?

"Absolutely," advised Sirus. Supplements are recommended only for people who aren't getting enough in their diet, she said. A calcium intake of up to 2,000 milligrams per day, including diet and supplements, appears to be safe, according to MedlinePlus, a Web site run by the National Institutes of Health. The best way to gauge how much you're getting is by reading food labels.

Okay. So what do I need to eat? Here are some common foods that contain these nutrients:

Dairy foods -- including milk, cheese and yogurt -- are a major source of calcium, reports the ODS. Others include yogurt, sardines, tofu, orange juice, salmon, pudding, cottage cheese, spinach, instant breakfast drinks, calcium-fortified cereal, turnip greens, kale, ice cream, calcium-fortified soy beverages, Chinese cabbage, tortillas, sour cream, bread and broccoli.

And if you're a regular espresso drinker, you're already taking in more calcium than you thought. "You certainly don't need a calcium pill if you're consuming one latte every day," said McGowan.

Most milk products in the United States are fortified with 10 micrograms (400 international units) per quart of vitamin D, according to the ODS, though other dairy products generally don't contain the vitamin or have only small amounts. Some breakfast cereals may contain vitamin D, as do the following foods: cod liver oil, cooked salmon, cooked mackerel, tuna fish, sardines, margarine, pudding made with fortified milk, egg, cooked liver and beef, and Swiss cheese. ยท

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