Effects of Calcium, Vitamin D on Bone Density in the Elderly
ABSTRACT & COMMENTARY
Synopsis: Calcium and Vitamin D supplementation substantially reduces the risk of nonvertebral fractures among healthy women and men aged 65 or older.
Source: Dawson-Hughes B, et al. N Engl J Med 1997; 337:670-676.
This article describes a prospective, double-blind, placebo-controlled trial of calcium and vitamin D supplementation in healthy women and men aged 65 or older. The study participants were recruited from "the community." Dawson-Hughes and associates excluded any individuals with a history of serious disease such as renal disease, kidney stones, and cancer. In addition, any individual who received a medication that is known to affect calcium metabolism was excluded. Individuals with daily dietary calcium intake exceeding 1500 mg were also excluded.
A total of 213 women and 176 men were studied. Each individual received either 500 mg of calcium and 700 IU of vitamin D a day or a placebo. Each individual was required to have bone mineral density examinations, as well as numerous laboratory tests every six months during the three years of the study. Dual-energy x-ray absorptiometry was used to assess bone mineral density in the hip, spine, and total body.
A number of individuals discontinued participation in the trial. The most common reasons were loss of interest, moving, or occurrence of an unrelated illness. Only 20 individuals withdrew from the study because of medication-related problems. The discontinuation rate was similar in the placebo and treatment arms.
At the end of three years, the women in the study who received vitamin D and calcium supplementation had an increase in total body bone mineral density when compared to the placebo group. However, when the femoral neck and lumbar spine were evaluated separately, the difference was not statistically significantly different. The males in the study had an increase in total bone mineral density, as well as an increase at the femoral neck and the lumbar spine. The authors conclude that the supplementation they used leads to a small but significant reduction in bone loss.
When nonvertebral fractures were examined, the authors found a marked decrease in the number occurring in those who received supplementation. Thirty-seven fractures occurred in the total group. Of these 37, 5.9% of the calcium/vitamin D treatment group sustained a nonvertebral fracture, whereas 12.9% of the placebo group had a nonvertebral fracture. The difference is highly statistically significantly different. Women in the placebo group sustained nearly a 20% occurrence of fracture during the three-year study. The authors conclude that calcium and vitamin D supplementation may "substantially reduce" the risk of vertebral fractures among healthy women and men aged 65 or older.
COMMENT BY KENNETH L. NOLLER, MD
Those of us in women's health care have for many years known of the beneficial effects of estrogen on the skeleton. We spend many hours trying to persuade reluctant patients to accept hormone replacement therapy because we know such treatment can markedly reduce (but, of course, not eliminate) the morbidity and mortality associated with falls in the elderly.
I wonder, however, how many of us take the time to assess whether our patients have an adequate calcium intake? Multiple studies have shown that both men and women older than 65 years rarely ingest 1500 mg of calcium, which is the suggested daily allowance. Indeed, as we age, we tend to consume fewer and fewer dairy products-the primary source of calcium and vitamin D. (For example, I have no idea when I last drank a whole glass of milk. Surely, it has been more than two decades.) It does little good to use hormone replacement therapy or bisphosphonates to counteract bone loss unless there is also dietary calcium available to put into the bones.
This article clearly shows that calcium and vitamin D alone are useful. This is important information for those women who refuse hormone replacement therapy or who cannot take it because of other medical illnesses. While the results of this study are not nearly as positive as those who use hormone replacement therapy and/or bisphosphonates, the gains through diet alone were substantial. (Dr. Noller is Professor and Chairman, Department of OB/GYN, University of Massachusetts Medical Center, Worcester.)
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