Calcium intake and peak bone mass.

Studying the relationship between calcium intake and peak bone mass in adolescent women is complicated by several factors. Calcium intake and calcium absorption are interrelated and can vary widely for the same individual, as well as among individuals. Modifiable determinants that affect bone gain in the peripheral skeleton do not necessarily have the same effect on the axial skeleton. In addition to these physiological factors, differences in study design make comparisons difficult. Study cohorts have varied in age, size, and pubertal status; bone measurements have been made at different sites with different equipment; and calcium intakes have been measured in different ways. Other important variables include endocrine maturation patterns and physical activity levels. Given this complex relationship, the amount of calcium young women need to achieve peak bone mass remains unclear. There is no convincing evidence, however, that they need more than 900 mg/day.