Does Calcium Help Bones?

Feb. 15, 2006 — -- Taking calcium and vitamin D supplements for several years can help older women reduce the risk of hip fractures, according to the results of a long-term, comprehensive, federally funded study by the Women's Health Initiative.

The study, published in the Feb. 16 issue of the New England Journal of Medicine, tracked 36,282 women ages 50 to 79 for seven years, half of whom took a daily dose of 1,000 milligrams of calcium combined with 400 international units of vitamin D3, while the other half took placebos.

The results: The calcium-vitamin D group of women who consistently took their supplements as directed showed a 29 percent reduction in the risk of hip fractures, while all women over 60 showed a 21 percent reduction. Or, put another way, there were 39 hip fractures per 10,000 women per year in the group taking the supplements, and 45 in the placebo group.

Although hip fractures were significantly reduced, the supplement did not affect overall bone density scores very much. On average, they improved by about 1 percent for women taking the supplements compared with those taking a placebo.

The rather low change in bone density likely means that taking the two nutrients late in life offers limited benefit, particularly for older women or those at risk of developing osteoporosis, said J. Edward Puzas, an orthopedics professor at the University of Rochester School of Medicine and Dentistry in Rochester, N.Y.

"I think the general public is looking for rapid reversals," Puzas said. "To assume that a short course of calcium and vitamin D will reverse the effects of many years on a poor diet or the effects of osteoporosis is asking too much."

So older women may want to take extra precautions, said Dr. Rebecca Jackson, an osteoporosis specialist at Ohio State University.

"For women over 65 or for women at especially high risk of osteoporosis, they should really discuss whether ... additional bone-active agents are appropriate," she said, referring to prescription medications such as Fosamax or Boniva.

The Drawback: Kidney Stones

Taking calcium and vitamin D also had little impact on spine or wrist fractures. However, hip fractures are by far the most debilitating fractures older women experience, Jackson said, so there's still a compelling reason for women to take supplements.

However, younger women probably don't need to take supplements, because their risk of fractures is low, experts said.

But they should try to obtain the recommended daily intake of the two nutrients by eating a calcium-rich diet and by getting daily sunlight, which helps the body create vitamin D, said Dr. Elizabeth G. Nabel, director of the federal National Heart, Lung and Blood Institute.

The study found that the one main drawback to taking the supplements was that they increased the risk of kidney stones. Nabel said women should discuss this risk with their doctor.

The study also examined whether calcium and vitamin D supplements could possibly lower the incidence of colorectal cancer. No difference was found between the two groups.