Calcium and vitamin D produce modest bone benefit for healthy postmenopausal women

The largest study ever done of calcium and vitamin-D supplementation in healthy postmenopausal women found rather small improvements in bone-mineral density (BMD) and in hip-fracture risk, but lead investigator Dr Rebecca D Jackson (Ohio State University, Columbus) tells rheumawire that the supplements are a worthwhile strategy for many women

“This study shows that healthy postmenopausal women, especially those over 60, can gain modest benefit in preventing hip fractures and preserving bone density from taking calcium and vitamin D. Women over 60 had a significant 21% reduction in hip fractures (six fewer fractures per 10 000 women). Women [of all ages] who took the full dose experienced a significant 29% decrease in hip fractures (four fewer fractures per 10 000 women),” Jackson said.Calcium, vitamin D not enough to protect bone healthThe data are from the Women’s Health Initiative (WHI), a series of studies sponsored by the US National Heart, Lung, and Blood Institute to examine causes and prevention of diseases affecting older women. Previous WHI studies have involved hormone therapy, low-fat diets, and heart disease.The 36 282 healthy postmenopausal women (age 50 to 79) recruited for the WHI were randomized to daily 1000 mg of elemental calcium as calcium carbonate with 400 IU of vitamin D3 or to daily placebo. Subjects were followed for 7.0 years.The study’s major findings were:- Women taking calcium/vitamin D had a statistically nonsignificant 12% reduction in hip-fracture risk. Rates of vertebral and lower arm/wrist fractures did not change. – Women who took at least 80% of the planned dose of calcium/vitamin D had a 29% reduction in risk of hip fracture. – Calcium/vitamin-D supplementation increased the risk of kidney stones by 17%. – The calcium/vitamin-D subjects had significantly greater preservation of total hip BMD at years three (+0.59% vs placebo), six (+0.86%), and nine (+1.06%).According to the investigators, “The trial demonstrated that calcium with vitamin-D supplementation diminishes bone loss at the hip, but the observed 12% reduction in the incidence of hip fracture (the primary outcome) was not statistically significant. There were no significant reductions in the incidence of clinical vertebral fractures, fractures of the lower arm or wrist, or total fractures.”Jackson points out several factors that should be considered in putting the data from this study into context. The first is that, perhaps reflecting increasing awareness of the importance of osteoporosis risk over the years of the study, actual fracture rates in both the treatment and control group were much lower than had been expected. That change reduced the power of the study to 48% for detecting a greater reduction in hip-fracture risk with calcium/vitamin D. Other possibly confounding factors are use of a 400-IU vitamin D dose rather than the 600 IU used in some other studies, the higher-than-anticipated body-mass index of the study subjects (who were thus likely to have stronger than expected bones), and recruitment of fewer women over age 70 than had been expected.”The most important take-home point for rheumawire readers would be that women, particularly those over 60, should consider taking calcium and vitamin-D supplements for bone health. To guard against bone loss or hip fracture, it is recommended that women consume 1200-mg calcium and 400 to 600 units of vitamin D through diet and supplements combined. For women over 65 or at high risk for osteoporosis or fracture, further assessment with bone-mass testing and consideration of a bone-active agent for additional fracture reduction might be appropriate,” Jackson saidIn an accompanying editorial, Dr Joel S Finkelstein (Massachusetts General Hospital, 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. This study should help correct this important misconception and allow more women to receive optimal therapy for bone health. [2]” (Source:[1] Jackson RD, LaCroix AZ, Gass M, et al. Calcium plus vitamin D supplementation and the risk of fractures. N Engl J Med 2006; 354:669-683. [2] Finkelstein JS. Calcium plus vitamin D for postmenopausal women- bone appetit? N Engl J Med 2006; 354:750-752.Joint and Bone: Rheumawire: Janis Kelly: February 2006.)