Adolescents: at increased risk for osteoporosis?

Perhaps the most important factor in the primary prevention of osteoporosis is the attainment of an optimal peak bone during adolescence. In addition to endogenous factors, such as genetic and ethnic background, environmental factors such as dietary habits, physical activity, and sex hormone therapy, influence the accretion of bone mass during this critical period of skeletal growth. First, calcium dietary intake in adolescents is generally well less than the current recommended RDA of 1200 mg/day. Multiple studies of children and adolescents have demonstrated increases in bone mass with dietary calcium supplementation. Second, regarding physical activity, the overall impression is that a moderate amount of particularly weight-bearing exercise has a positive impact on bone. There appears, however, to be a threshold of intensity of physical activity over which a negative impact on bone occurs, particularly when the exercise is of an anaerobic nature or occurring in very thin, amenorrheic participants. Third, previous research suggests that the various forms of hormonal contraception exert differing effects on bone mass in adolescents, with levonorgestrel implants and combined oral contraceptives may be associated with a more positive effect on bone mass compared with that observed with depot medroxyprogesterone acetate. From a clinical perspective, approaches to optimizing peak bone mass in adolescents would include increasing calcium intake, whether in the form of dairy products, fortified foods, or supplements as well as encouraging participation at a moderate level, in weight-bearing exercise. Last, in adolescents with extensive risk factors and predicted long duration of use, subdermal implants or combined oral contraceptives may be the optimal hormonal methods of birth control.