An 18-year prospective study of dietary calcium and bone mineral density in the hip.

The object of this study was to determine whether a single 24-hour diet recall of calcium intake obtained an average of 18 years previously would predict bone mineral density (BMD) in the hip in older men and women. A prospective population-based cohort study was done in Rancho Bernardo, California. Between 1973 and 1975, a 24-hour diet recall was obtained in 140 men and 220 women aged 45 and older by a trained interviewer using food models and containers. Responses were coded by the Nutrition Coordinating Center, University of Minnesota. Between 1988 and 1991, BMD in the femoral neck, trochanter, and intertrochanter was measured using dual-energy x-ray absorptiometry. Results showed that age-adjusted mean BMD levels increased significantly with increasing tertile of calcium intake at all hip sites in women, with the most striking difference at the femoral neck. These associations persisted after adjustment for body mass index, smoking, exercise, alcohol intake, use of estrogen replacement therapy, and number of years postmenopausal. No significant trends were seen for men at any hip site. It is concluded that low dietary calcium predicts low BMD in older women independent of other major determinants of BMD.