In Northern China, Ca intake and serum vitamin-D level of adolescents are low due to non-dairy-based diets and insufficient sunshine exposure. Maximisation of bone mineral accretion in childhood and adolescence requires adequate dietary calcium (Ca) intake and body vitamin-D status. This study focused on nutritional adaptation in Chinese adolescents under these adversed conditions by determining Ca absorption (CaAbn) and urinary calcium excretion (CaEx).

16 healthy individuals (12 girls, 4 boys) aged 9–17-y were recruited from Beijing during December. CaAbn was determined by a dual stable-isotope technique (44Ca and 42Ca) coupled with a Thermal-Ionization -Mass-Spectrometer.

Mean ± sd Ca intake, 24-h CaEx, and serum 25-(OH) vitamin D3 were 603 ±158 mg/d, 87.5 ± 59.2 mg/24-h and 13.7 ± 4.8 ng/mL respectively. Mean serum 25-(OH) vitamin D3 reached the lower normal-limit of 11 ng/mL. 24-h-CaEx (< 100 mg/d) reflected a higher efficiency of Ca retention. CaAbn was found 57.4 ± 15.4% which was significantly higher than the U.S. counterparts (25–34%; Ca intake: 925 mg/d), P< 0.05. However, CaAbn in the current study was comparable to a group of healthy Hong Kong children aged 7-y (CaAbn: 54.8%, Ca intake: 862 mg/d, serum 25-(OH) vitamin D3:33.3 ng/mL).

The study showed that growing individuals with suboptimal vitamin D status are still capable of enhancing calcium absorption and reducing urinary calcium excretion to allow adequate bone Ca accretion.