Role of nutrition and exercise in osteoporosis.

Both adequate nutrition and exercise are essential for development of peak adult bone mass and maintenance of bone during aging. The optimal dietary level of a nutrient may vary from individual to individual and may change with age, intake of other nutrients, disease, drug therapy, or sex hormone status. Effects on spinal trabecular bone may not parallel effects on axial cortical bone. Calcium nutrition is important in the prevention of osteoporosis, as calcium is a major constituent of bone. The intake of calcium among most American adults is below the levels recommended by public health agencies. There have been no adequate prospective studies to determine the optimal intake of calcium for preservation of bone mass in young or middle-aged adults, although calcium balance studies indicate that premenopausal women require approximately 1,000 mg of calcium per day. The negative calcium balance of early menopause may be ameliorated by 1,000 mg of calcium per day; however, there is no proof that greater intakes fully reverse the effects of estrogen deficiency. Calcium requirements of both elderly men and women are likely to be greater (between 1,000 and 1,500 mg per day) due to an age-related decrease in the efficiency of intestinal calcium absorption. The optimal level of weight-bearing exercise for maintenance of bone mass in old age is probably similar to that of an active young adult. Maintenance of this activity level in middle and old age improves bone mass. An exercise prescription for elderly individuals must include an appraisal of cardiovascular and muscular-skeletal health and be designed to minimize the risk of trauma during exercise.