[Body vitamin D content and its relationship with body composition of children in Huairou district of Beijing].

Objective: To analyze vitamin D concentration and its association with body composition of children in Huairou district of Beijing, to provide evidence for evaluation and improvement of nutritional status of vitamin D in children.

Methods: Totally, 381 children aged 7 - 11 years were recruited in Huairou district of Beijing (40.3 degrees N). Samples of overnight fasting venous blood (drawn between 0630 and 0900) were obtained in late March. Serum 25-hydroxyvitamin D [25(OH)D]concentration was determined by ELISA kits (IDS Ltd, UK). Body composition indices of the whole body, the distal and proximal forearm were measured using dual-energy X-ray absorptiometry (DEXA, Norland, USA).

Results: The average serum 25(OH)D concentration of all subjects was (44.4 +/- 12.5) nmol/L. The percentage of vitamin D insufficient [serum 25(OH)D < / = 50 nmol/L] reached as high as 68.5% (261 people). The 25(OH)D concentration of boys (46.3 nmol/L +/- 13.3 nmol/L)was significantly higher than that of girls (42.0 nmol/L +/- 11.1 nmol/L), (t = 3.38, P < 0.01). Between the serum 25(OH)D concentration and lean body mass of proximal forearm, distal forearm, whole body, and four limbs, significant positive correlations (r = 0.13 - 0.19, P < 0.05)were observed. After age, gender, height and weight were under controlled for, correlations between the serum 25(OH)D concentration and lean body mass at proximal forearm, and the two lower limbs still existed (r = 0.12-0.14, P < 0.05). The serum 25(OH)D concentration, the percentage of body fat at proximal forearm, and distal forearm were negatively correlated (r = -0.14, P < 0.05; r = -0.11, P < 0.05). However, after adjusting for confounding effects, this correlation disappeared. No significant correlation between the serum 25(OH)D concentration and body fat was observed at any position.

Conclusion: Vitamin D deficiency was common in children of suburb area of Beijing. Vitamin D status was positively associated with the lean body mass.