Abstract
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.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
