printable versionWHI study questions calcium's benefits
BY SUSAN IPAKTCHIAN
Marcia Stefanick
Taking calcium and Vitamin D slightly decreased the risk of hip fractures in older women, but not the risk for other types of fractures or for colorectal cancer, according to the latest findings from the federally funded Women's Health Initiative. Additionally, the supplements slightly increased the incidence of kidney stones.
A researcher at the School of Medicine who helped oversee the WHI study said the results don't change current recommendations that women over age 50 should consume 1,200 milligrams of calcium and 400-600 international units of Vitamin D each day to maintain their bone health. However, Marcia Stefanick, PhD, professor of medicine and chair of the WHI steering committee, noted that adequate levels of these nutrients don't have to come from supplements."You may be able to get enough calcium and Vitamin D through the foods you eat," she said.
The findings were published in the Feb. 16 issue of the New England Journal of Medicine. They are the latest clinical results from the WHI, a 15-year, broad-based look at the causes and prevention of diseases affecting older women. Previous WHI studies have involved hormone therapy, low-fat diets and heart disease.
The calcium/Vitamin D study tracked more than 36,000 postmenopausal women between the ages of 50 and 79 for seven years. Researchers wanted to determine whether women who took supplements could reduce the risk of bone fractures, especially hip fractures, and colorectal cancer.
Half of the trial participants were randomly assigned to take daily supplements of 1,000 mg of elemental calcium and 400 IU of Vitamin D3, the recommended dosage to prevent osteoporosis that was in effect when the WHI trial was designed in the early 1990s. The remaining women were given a placebo.
The study found that women assigned to take the supplement had a 12 percent reduction in hip fractures, a difference that was not statistically significant. While some of the women did not adhere completely to the supplement regimen, the study found that those who took 80 percent or more of the recommended dosage had a 29 percent decrease in hip fractures.
The supplements didn't make a difference in reducing the rates of spine, wrist and other fractures, or in reducing the risk of colorectal cancer.
Although most women tolerated the supplements well, there was a 17 percent increase in the rate of kidney stones.
Calcium and Vitamin D have long been staples in the effort to improve bone health among older women, who are four times more likely than men of the same age to suffer from osteoporosis. Forty percent of women over age 50 experience a fracture of the hip, spine or wrist in their lifetime.
Additionally, observational studies have suggested that a higher intake of calcium and Vitamin D could lower the risk for colorectal cancer, but results from past clinical trials have been mixed. Colorectal cancer is the second-leading cause of cancer deaths in the United States for men and women combined.
Based on the new findings, Stefanick said women should still make sure they get enough calcium and Vitamin D for bone health, but that they shouldn't expect this to prevent colorectal cancer. "Because we don't have good evidence of how to prevent colorectal cancer, the importance of early detection through regular screenings should be emphasized for both women and men from age 50 onward," Stefanick said.