Press Releases: Northwest
February 16, 2006
Federal study of calcium and Vitamin D supplements in women shows modest benefit for bone health but none for colorectal cancer
861 Northwest women participate at Kaiser Permanente's Center for Health Research
PORTLAND, Ore. – Calcium and vitamin D supplements taken by healthy postmenopausal women provide a modest benefit in preserving bone mass and lower the risk of hip fracture in some groups of women, but they do not appear to prevent other types of fractures or colorectal cancer. These findings from the federal Women's Health Initiative (WHI) which included 871 women in Oregon and Southwest Washington, appear in two articles in the February 16 issue of the New England Journal of Medicine.
"I have two suggestions for older women based on these findings," says Evelyn Whitlock, MD, MPH, principal investigator for WHI at Kaiser Permanente's Center for Health Research (CHR) and a co-author of both articles. "The first is fairly simple - if you are a postmenopausal woman between the ages of 50 and 79, do not expect calcium and vitamin D supplements to lower your risk of colorectal cancer. The best thing you can do for yourself is to make sure you get regular screenings. The second is more complicated. Taking these supplements increased hip bone density in older women, but only women over age 60 and women who took the full supplement dose had a significantly reduced risk of a hip fracture. So if your goal is to reduce your risk of hip fracture by taking supplements, my advice is to make sure you take the full recommended dose every day. For women over age 50, that's 1200 milligrams of calcium carbonate and 600 IUs of vitamin D3."
Nationwide, 36,282 postmenopausal women enrolled in the WHI Calcium with vitamin D (CaD) trial. In the greater Portland area, 871 women joined the study through CHR. After seven years, women who took the supplements had a small but statistically significant one percent higher hip bone density than women who received placebos. During the study, 374 women had hip fractures. The fracture rates were 14 per 10,000 women per year in the supplement group compared to 16 per 10,000 per year in the placebo group, which was not a statistically significant difference. However, women who consistently took the full supplement dose had a significant 29 percent decrease in hip fractures. Women older than 60 also had a significant 21 percent decrease in hip fractures. The supplements had no significant effect on spine or total fractures.
Calcium and vitamin D supplements had no detectable effect on the incidence of colorectal cancer. There were similar rates of cancer in both groups - 13 cases per 10,000 women per year in the supplement group compared to 12 cases per 10,000 per year in the placebo group. There was no statistically significant difference between the two groups in the characteristics or severity of tumors, as well as no difference between groups in the number of polyps reported by the participants. When the investigators analyzed only the data obtained from women who took most of their study pills, there was still no difference seen from taking supplements.
Supplements were well tolerated by participants, and the only adverse effect found was a 17 percent increase in kidney stones. Kidney stones were reported by 449 women in the supplement group (34 cases per 10,000 per year) compared to 381 women in the placebo group (29 cases per 10,000 per year). Because hip fractures are considered to be more serious than kidney stones, the public health benefit on balance of taking the supplements outweighs the risks.
"We owe a profound debt to the women who joined and have continued to participate in WHI over more than 10 years," says Dr. Whitlock. "All the women in this calcium and vitamin D study also participated either in the hormone replacement studies or the lower-fat diet study. These women have also made - and will continue to make - a huge contribution to our collective understanding of the major diseases that affect women. Consider how generous more than 160,000 women across America have been in contributing health and medical information to this research study - not with the hope of helping themselves but in the interest of their children, grandchildren, and the generations to come. Now that the major results from this study are finally released, we want to publicly acknowledge our local WHI participants and say, once again, 'Thanks!'"
Kaiser Permanente's Center for Health Research, founded in 1964, is a non-profit research organization whose mission is advancing knowledge to improve health.
Kaiser Permanente is America's leading integrated health care organization, serving more than 8.4 million people nationwide. Founded in 1945, Kaiser Permanente serves the health needs of 475,000 people in Oregon and Southwest Washington.
