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

The acquisition of radial mineral density was evaluated in relation to anth ropometric characteristics, menarche status, calcium intake and physical ac tivity in a healthy young female population (200 girls and 100 women, respe ctively 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 evalua ted by a detailed Food Frequency Questionnaire and confirmed by a 3-day rec ord. A questionnaire on energy expenditure was used to assess physical acti vity in each participant. Morning blood samples were drawn from fasting gir ls to measure 25-hydroxycalciferol (25 OH-D). We found current calcium abov e the levels reported by Recommended Dietary Allowances (RDA) in only 31% o f 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 p ubertal stage. Bone density was also significantly related to age, weight a nd height in postmenarcheal adolescents, while in girls before and after me narche, no relation was observed between radial BMD and calcium intake or p hysical activity. In the presence of comparable calcium-intake values recor ded in pre- and in postmenarcheal girls, the latter subgroup displayed a ma rked 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 acquisiti on during pubertal development.