Critical years and stages of puberty for radial bone mass apposition during adolescence

The acquisition of radial mineral density was evaluated in relation to anthropometric characteristics, menarche status, calcium intake and physical activity in a healthy young female population (200 girls and 100 women, respectively aged 11-16 yrs and 20-24 yrs) living in an area of Southern Italy. We performed bone mineral density (BMD) by dual energy X-ray absorptiometry on the ultradistal and middistal radius. Dietary calcium intake was evaluated by a detailed Food Frequency Questionnaire and confirmed by a 3-day record. A questionnaire on energy expenditure was used to assess physical activity in each participant. Morning blood samples were drawn from fasting girls to measure 25-hydroxycalciferol (25 OH-D). We found current calcium above the levels reported by Recommended Dietary Allowances (RDA) in only 31% of women and 6% of girls. BMD steadily increased up to the age of 16 and was increased in postmenarcheal girls compared to premenarcheals of the same pubertal stage. Bone density was also significantly related to age, weight and height in postmenarcheal adolescents, while in girls before and after menarche, no relation was observed between radial BMD and calcium intake or physical activity. In the presence of comparable calcium-intake values recorded in pre- and in postmenarcheal girls, the latter subgroup displayed a marked increase of 25 OH-D serum levels. Our study revealed a calcium intake lower than the RDA in a large percentage of healthy girls and young women, and emphasized the importance of menarche occurrence in bone mass acquisition during pubertal development.