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J. J. B. ANDERSON, Department of Nutrition, Schools of Public Health and Medicine, University of North Carolina, Chapel Hill, Chapel Hill, NC 27599-7400

Dietary consumption of calcium by adolescent girls, at 11 years of age, falls significantly below recommended intakes. Except for protein and phosphorus, intakes of other nutrients important for bone health, such as magnesium and vitamin K, typically fall below recommended intakes because of insufficient caloric consumption. Since many adolescent girls are concerned about body weight and appearance, their eating habits do not usually meet the recommended numbers of servings each day from the food pyramid. Despite these dietary compromises, adolescent girls may be able to establish healthy values of bone mineral content (BMC) and bone mineral density (BMD) by the time their adult height is achieved, (16 years on average). A major factor that promotes more optimal bone modeling, (bone growth - formation first and resorption second), is regular physical activity during the growing years-despite the suboptimal consumption of calcium and other critical micronutrients. Once the modeling of the skeleton is completed (or the growth plates are no longer active), bone remodeling, (resorption first and formation second), becomes the process for shaping the bones. Nutrient requirements remain approximately the same from 11 to 20 years of age. Many adolescent females have both low calcium intakes and little or no physical activity. They may have additional nutrient deficits and other behaviors that contribute adversely to skeletal development. Young women are projected to live, on average, to 80 years old, but they may not develop sufficient BMC and BMD values to achieve 80 years without fractures, even perhaps a hip fracture, the most debilitating of all and an important precursor of death. The view that adolescent nutrition is critical for bone health throughout the life cycle has been confirmed by recent observational studies.