Physical Activity and Exercise Affect Intestinal Calcium Absorption: a Perspective Review

Moderate endurance exercise and physical activity have a positive effect on calcium metabolism and bone by increasing bone mineral density and reducing urinary calcium loss, whereas immobilization has the opposite effects. However, little is known regarding effects of exercise on the intestinal calcium absorption, which is the sole source of calcium for bone formation. Intestinal calcium absorption affects bone mass and bone strength both of which directly contribute to exercise performance. Previous investigations in humans and rats suggested that endurance exercise stimulated intestinal calcium absorption in vivo; however, the underlying mechanisms remain controversial. On the other hand, immobilization decreased the intestinal calcium absorption partly by reducing the serum level of 1,25dihydroxyvitamin D3, one of the major calcium-regulating hormones, and the expression of several calcium transporter genes. Further studies deserve to demonstrate in depth the molecular mechanisms of enhanced calcium absorption following different modes of exercise training, such as swimming and running, in different sex and/or age groups. The obtained knowledge would help sport scientists and physicians to design appropriate calcium supplementation and exercise training regime for athletes. (J. Sports Sci. Technol 2007; 7(1): 171–181)