ORAL CALCIUM SUPPRESSES BIOCHEMICAL MARKERS OF BONE-RESORPTION IN NORMAL MEN

Calcium supplementation decreases bone resorption and retards bone los s in women. There is little information about the effects of calcium s upplementation in men. The effects of a 1-g oral calcium load at 0900 on bone-related biochemical variables were evaluated in 13 normal men (aged 51-70 y). Calcium administration was associated with increases i n plasma ionized calcium (P < 0.001) and urinary calcium (P < 0.001), and a decrease in plasma parathyroid hormone (P < 0.001). There was a nonsignificant trend (r = -0.47, P = 0.11) for the decrease in plasma parathyroid hormone to be related to radiocalcium absorption. After th e calcium load there were decreases in the urinary hydroxyproline-crea tinine ratio from 11 +/- 1.1 to 7.9 +/- 0.6 (P < 0.01), the urinary de oxypyri dinoline-creatinine ratio from 14.0 +/- 1.8 to 10.1 +/- 0.9 (P < 0.05), and the urinary pyridinoline-creatinine ratio from 52 +/- 5 to 40 +/- 3 (P < 0.01) between baseline and 6 h. There was no change i n plasma osteocalcin. These observations indicate that a 1-g calcium l oad suppresses biochemical markers of bone resorption for greater than or equal to 6 h in normal men and support the concept that calcium su pplementation may be useful in the prevention of bone loss in men.