THE EFFECTS OF CALCIUM SUPPLEMENTATION (MILK POWDER OR TABLETS) AND EXERCISE ON BONE-DENSITY IN POSTMENOPAUSAL WOMEN

The etiology of age-related bone loss is unclear but both lack of exer cise and dietary calcium deficiency have been implicated in its causat ion. This 2-year randomized placebo-controlled study was designed to e xamine the effects of increased dietary calcium and exercise in 168 wo men who were more than 10 years postmenopausal. The subjects were rand omized into one of 4 groups: placebo, milk powder containing 1 g of ca lcium, calcium tablets 1 g/night, and calcium tablets 1 g/night and an exercise regimen. The exercise group aimed to undertake 4 h of extra weight-bearing exercise per week and were undertaking 10% more activit y than other groups at 2 years. Bone mineral density at the lumbar spi ne, three hip sites, and two sites of the tibia close to the ankle joi nt were measured at 6 month intervals. Dietary intake was evaluated by a weighed food record, exercise was evaluated by an exercise diary, a nd blood and urine samples were obtained to examine effects on calcium homeostasis. Individual data points were compared using repeated meas ures ANOVA and least squares regression. Calcium supplementation by ei ther the calcium tablets or the milk powder resulted in cessation of b one loss at the intertrochanteric hip site (placebo, calcium tablets, calcium and exercise, milk powder -0.81, +0.17, +0.23, and +0.07% per year, respectively; p < 0.05 for all supplementation groups compared w ith placebo) with similar results at the trochanteric hip site. The ca lcium and exercise group had less bone loss at the femoral neck site w hen compared with calcium supplementation alone (placebo, calcium tabl ets, calcium and exercise, milk powder -0.67, -0.18, +0.28, and -0.18% per year, respectively; p < 0.05 for calcium and exercise compared wi th calcium alone). There was a significant reduction in the rate of bo ne loss at the ultradistal site of the tibia (placebo, calcium tablets , calcium and exercise, milk powder -2.5, -1.6, -1.0, and -1.5% per ye ar, respectively; p < 0.05 for all supplementation groups compared wit h placebo). There was no significant bone loss-at the spine site in an y group. These data support the implementation of a simple public heal th regimen to prevent age-related bone loss with calcium supplementati on either by calcium tablet or by milk powder. The extra effect of exe rcise plus calcium at the femoral neck site suggests a site-specific e ffect of physical activity on bone density in addition to its possible effect to prevent fracture by maintenance of muscle strength and coor dination.