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Public Health & Education | Calcium, Vitamin D Supplements Have Little Effect on Women's Bone Density, Risk of Colorectal Cancer, Study Says

Thursday, February 16, 2006

Calcium and vitamin D supplements provide little benefit in preventing broken bones or colorectal cancer in healthy women ages 50 to 79, according to studies that are part of the NIH-funded Women's Health Initiative published in the Feb. 16 edition of the New England Journal of Medicine, the New York Times reports (Kolata, New York Times, 2/16).

In one of the NEJM studies, Rebecca Jackson, an endocrinologist at Ohio State University Medical Center, and colleagues randomly assigned 36,282 women ages 50 to 79 enrolled in WHI to take either one daily pill containing 1,000 milligrams of elemental calcium and 400 international units of vitamin D3 or daily placebo pills (Forelle/Pagan Westphal, Wall Street Journal, 2/16). The women were followed for an average of seven years as researchers examined the impact of the pills on bone density, colorectal cancer and bone fractures (New York Times, 2/16). The study finds the group of women taking the supplements had a 1% higher hip bone density and a 12% lower chance of having a hip fracture than the group taking the placebo pills (Rubin, USA Today, 2/16). However, the incidence of hip bone fractures among the group taking supplements -- 14 per every 10,000 women -- was not significantly different from the group taking placebo pills, who had an incidence of 16 fractures per every 10,000 women, the study finds (Gellene, Los Angeles Times, 2/16). About 20% of the women in the group taking supplements did not take the pills regularly, the study finds. Those who adhered to the regimen for most of the study had about a 29% lower chance of a hip fracture than the group taking the placebo pills, according to the study (Emery, Reuters, 2/15). The study also finds that women over age 60 had a 21% lower chance of hip fracture if they were in the supplement group (Donn, AP/Yahoo! News, 2/16). Researchers found that the supplements did not decrease the risk of spine or wrist fractures, the Los Angeles Times reports (Los Angeles Times, 2/16). About 10 million people in the U.S. are living with osteoporosis, a thinning of the bones that increases the risk of broken bones (Stein, Washington Post, 2/16).

Colorectal Cancer, Kidney Stone Findings

In a related NEJM study that examined the same group of women for incidence of colorectal cancer, researchers found no statistically significant difference in the incidence of the cancer between the two groups (Fay Cortez, Bloomberg, 2/16). According to USA Today, this conflicts with previous findings that showed a benefit from ingesting calcium. Study authors said that this might be because the women were permitted to take calcium and vitamin D supplements along with the pills in the study, meaning that women taking the placebo pills still could have been ingesting high doses of calcium (USA Today, 2/16). Jean Wactawski-Wende, lead author of the study and an associate professor at the University of Buffalo School of Public Health and Health Professions, said that colorectal cancer "takes 10 to 20 years to develop," and the study's seven-year length might not have been "enough time to show a benefit" (Ricks, Long Island Newsday, 2/16). The study also finds that calcium supplements led to a 17% greater risk of kidney stones, Reuters reports (Reuters, 2/15).

Reaction

"Based on our findings, women, particularly those over 60, should consider taking calcium with vitamin D for bone health and to guard against fracture," Jackson said (Washington Post, 2/16). However, in a related NEJM editorial, Joel Finkelstein, a physician at Massachusetts General Hospital in Boston, writes, "With the widespread marketing of calcium and vitamin D, many women believe that they are completely protected against the development of osteoporosis if they are taking these supplements," adding, "This study should help correct this important misconception and allow more women to receive optimal therapy for bone health" (Reuters, 2/15). NIH said the study supports government recommendations that postmenopausal women take 1,200 milligrams of calcium daily. John Hathcock -- vice president for scientific and international affairs for the Council for Responsible Nutrition, a trade association representing the dietary supplement industry -- said that, while the study was "big, powerful and well done," many of the participants had sufficient calcium levels before the trial began, which left "less room for improvement." According to the Journal, 38.5% of participants who took the supplements and 39.2% of participants who took the placebo ingested more than 1,200 milligrams of calcium daily before the trial began (Wall Street Journal, 2/16). Susan Ellenberg, a statistician at the Center for Clinical Epidemiology and Biostatistics, said, "I think it's pretty clear that if there's any effect [from the supplements] at all, it's extremely modest. Even when you do those questionable subgroup analyses, there's just a barely significant effect, and that's in a very, very large group" (New York Times, 2/16). Researchers said that although the studies analyzed women, there is no reason to assume the findings would not apply to men as well, the Washington Post reports (Washington Post, 2/16).

Reprinted with permission from kaisernetwork.org. You can view the entire Kaiser Daily Women's Health Policy Report, search the archives, and sign up for email delivery at www.kaisernetwork.org/dailyreports/women. The Kaiser Daily Women's Health Policy Report is published for kaisernetwork.org, a free service of The Henry J. Kaiser Family Foundation. (c) 2005 Advisory Board Company and Kaiser Family Foundation. All rights reserved.

 

 

 

 

 

 
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