Calcium and vitamin D may help maintain bone health in healthy postmenopausal women under 65. But the supplements probably aren't enough by themselves to prevent falls and fractures in women who have osteoporosis, or face a heightened risk of the bone-thinning disease. Women 65 and older and those with osteoporosis, or risk factors for the condition such as cigarette smoking, may need more aggressive treatment to keep their bones strong. Researchers from the Ohio State University in Columbus, USA, compared daily supplementation with 1,000 milligrams of calcium and 400 international units of vitamin D with placebo in 36,282 women aged 50 to 79, all of whom were postmenopausal and healthy. After seven years, women on the supplements showed a slight but significant increase in bone density at the hip and an increased risk of kidney stones. When the researchers limited their analysis to women who had consistently taken the supplements, the effect was stronger, showing a nearly 30 percent reduced risk of hip fracture. There are a number of reasons why the study didn't show a greater benefit for vitamin D and calcium; for example, over half of study participants were on hormone replacement therapy, which is known to reduce fracture risk. Also, studies that have found benefits for calcium and vitamin D have used higher doses of the vitamin - at least 700 international units. The above results add to the existing body of evidence that calcium with vitamin D supplementation by itself is insufficient therapy to prevent fractures in postmenopausal women, though it may be beneficial in selected subgroups, such as women over the age of 60 or those with a low intake of calcium and vitamin D.
The New England Journal of Medicine,
February 2006