NUTRITION, EXERCISE, AND BONE STATUS IN YOUTH

The maximal amount of bone mass gained during growth (peak bone mass) is an important determinant of bone mass in later life and thereby an important determinant of fracture risk. Although genetic factors appea r to be primary determinants of peak bone mass, environmental factors such as physical activity and nutrition also contribute. In this artic le, bone growth and maintenance are reviewed, and mechanisms are descr ibed whereby physical activity can affect bone mass. Studies addressin g the effects of physical activity on bone status in youth are reviewe d: Although conclusive data are not yet available, considerable eviden ce supports the importance of activity, especially activity initiated before puberty. The critical role of energy in bone growth is outlined , and studies assessing the impact of calcium intake during childhood and adolescence are reviewed. Although results of intervention trials are equivocal, other evidence supports a role for calcium intake durin g growth. Recommendations for physical activity and nutrition, directe d to children and adolescents, are presented.