Calcium Supplements and Fracture Prevention

A 62-year-old healthy woman presents for routine care. She has no history of fracture, but she is worried about osteoporosis because her mother had a hip fracture at 72 years of age. She exercises regularly and has taken over-the-counter calcium carbonate at a dose of 1000 mg three times a day since her menopause at 54 years of age. This regimen provides 1200 mg of elemental calcium per day. She eats a healthy diet with multiple servings of fruits and vegetables and consumes one 8-oz serving of low-fat yogurt and one glass of low-fat milk almost every day. She recently heard that calcium supplements could increase her risk of cardiovascular disease and wants your opinion about whether or not she should receive them. What would you advise? T h e C l i nic a l Probl e m Both clinicians and patients are likely to be confused by the inconsistent and sometimes conflicting advice about the amount of calcium intake required to reduce the risk of fracture and, in particular, whether calcium supplements are necessary. Long-term calcium deficiency can clearly confer a predisposition to osteoporosis, 1 but many persons mistakenly believe that postmenopausal and age-related bone loss and the associated increase in susceptibility to fracture can largely be avoided with the use of calcium supplementation. Although some persons remain at risk for calcium deficiency, other persons, particularly those receiving calcium supplements, may receive more than the recommended daily intake. The complex and incompletely understood interaction between calcium and vitamin D intake complicates our understanding of the benefits and risks associated with either one alone. 2,3 For example, a recent randomized trial showed that even high doses of vitamin D 3 (4800 IU per day) had modest beneficial effects on calcium absorption (a 6% increase) among postmenopausal women with low serum levels of 25-hydroxyvitamin D. 4 Furthermore, a number of clinical trials have studied the combination of calcium plus vitamin D in various doses, but fewer trials have examined the effects of calcium alone on the skeleton. This review summarizes our current understanding of calcium intake as it re lates to fracture risk and discusses concerns about the safety of calcium supplements. Other reviews have addressed the physiology of calcium metabolism and the ongoing controversies about vitamin D. 2,5