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Study Finds Calcium, Vitamin D Supplements Help Improve Bone Mass But Don't Protect Against Most Fractures or Colorectal Cancer

Results of a recent study suggest that taking calcium and vitamin D supplements provide only a modest benefit in protecting bone mass and preventing hip fractures in some older women but do not protect against other types of fractures or colorectal cancer. In addition, the supplements were associated with an increased risk of kidney stones. The study results are somewhat surprising in that they show that calcium and vitamin D, while beneficial for increasing bone mass, provided less protection against hip fractures than expected. In the study, only women over 60 years of age who took the full intended dose of supplements were protected against hip fractures.

Researchers have long been studying ways to help prevent osteoporosis, is a degenerative bone disease characterized by a reduction in bone mineral density due to a loss of calcium and collagen. Osteoporosis is a threat to 28 million Americans and is currently one of the most under-diagnosed and under-treated disorders in medicine. It is estimated that one in two women over 50 will suffer an osteoporosis-related fracture in her lifetime.

"Given the serious public health burden of fractures associated with osteoporosis, it is important to learn as much as possible about ways to prevent and treat bone loss," said researcher Joan McGowan, PhD, of the National Institute of Arthritis and Musculoskeletal and Skin Diseases, in a Women's Health Initiative (WHI) news release.

In the study, researchers recruited 36,282 postmenopausal women, 50 to 79 years of age, who were already enrolled in a Women's Health Initiative (WHI) clinical trial. Half of the women received a daily dose of 1,000 milligrams of calcium carbonate combined with 400 IUs of vitamin D3. The other half of the study group received placebo (inactive) pills. The women were followed for an average of seven years.

The study results showed that women who took calcium and vitamin D supplements increased their bone density in their hips by 1% -- a small but statistically significant increase. According to a WHI news release, "During the trial, 374 women had hip fractures with a fracture rate of 14 per 10,000 cases per year in the supplemented group compared to 16 per 10,000 per year in the placebo group. This 12% reduction in hip fracture in those taking the calcium plus vitamin D supplement was not statistically significant; however, women who consistently took the full supplement dose experienced a significant 29% decrease in hip fracture. Women older than 60 had a significant 21% reduction in hip fracture. The supplements had no significant effect on spine or total fractures."

"This important study provides guidance for women on the risks and benefits of supplementing their diets with calcium and vitamin D," said Elizabeth G. Nabel, M.D., Director of the National Heart, Lung, and Blood Institute and the Women's Health Initiative (WHI), in a WHI news release. "The overall results suggest that women, particularly those over 60, should consider taking calcium and vitamin D for bone health but they should not expect these supplements to help prevent colorectal cancer."

The researchers also offered some explanation as to why they might have seen lower than expected reductions in hip fractures with calcium and vitamin D supplement use.

"Although 76% of women were still taking study pills at the end of the trial, only 59% were taking the intended number of pills," said Rebecca D. Jackson, MD, endocrinologist and the study's lead investigator at Ohio State University in Columbus, in a WHI news release. "In a secondary analysis, we found a significant 29% decrease in hip fracture risk among women who took most of their study pills - that's four fewer hip fractures for every 10,000 women per year," she said.

The Women's Health Initiative study will continue to investigate this and other issues affecting women's health. Women should talk to their physicians about the best course of action to help prevent bone fractures, osteoporosis, and colorectal cancers. In many cases, a calcium and vitamin D supplement may be appropriate in combination with other preventive measures.

Additional Resources and References

  • The study, "Calcium plus Vitamin D Supplementation and the Risk of Fractures," is published in the February 16, 2006 issue of The New England Journal of Medicine,
  • The February 15, 2006 Women's Health Initiative news release, "Calcium and Vitamin D Supplements Offer Modest Bone Improvements, No Benefits for Colorectal Cancer," was published on the WHI website,
  • To learn more about osteoporosis, please visit