Oral calcium suppresses biochemical markers of bone resorption in normal men.

Calcium supplementation decreases bone resorption and retards bone loss in women. There is little information about the effects of calcium supplementation 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 in 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 the calcium load there were decreases in the urinary hydroxyproline-creatinine ratio from 11 +/- 1.1 to 7.9 +/- 0.6 (P < 0.01), the urinary deoxypyridinoline-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 in plasma osteocalcin. These observations indicate that a 1-g calcium load suppresses biochemical markers of bone resorption for > or = 6 h in normal men and support the concept that calcium supplementation may be useful in the prevention of bone loss in men.