SEASONAL DEFICIENCY OF VITAMIN-D IN CHILDREN - A POTENTIAL TARGET FOROSTEOPOROSIS-PREVENTING STRATEGIES

Peak bone mass attained after skeletal growth is a major determinant o f the risk of developing osteoporosis later in life, hence the importa nce of nutritional factors that contribute to bone mass gain during in fancy and adolescence. An adequate supply of vitamin D is essential fo r normal bone homeostasis. This study was undertaken to determine what the levels are of 25-hydroxyvitamin D (25(OH)D) that may be considere d desirable in children and to assess if normal children maintain thes e levels throughout the year. Vitamin D metabolites and parathyroid ho rmone (PTH) serum levels were measured in 21 children in March and Oct ober, prior to and after the administration of a daily supplement of 2 5(OH)D (40 mu g for 7 consecutive days). There were inverse correlatio ns between basal 25(OH)D levels and supplementation-induced changes in serum 1,25(OH)(2)D (r = 0.57, p < 0.05) and PTH (r = 0.41, p < 0.05). When basal levels of 25(OH)D were below 20 ng/ml, the supplement indu ced and increase in serum 1,25(OH)(2)D; with basal 25(OH)D under 10-12 ng/ml, the supplement also decreased serum PTH. The lowest serum leve l of 25(OH)D in 43 normal children was somewhere between 12 and 20 ng/ ml. However, 31% of 51 children studied in winter had levels below 12 ng/ml, and ng/ml. Those children are likely to have suboptimal bioavai lability of vitamin D, which might hamper their achievement of an adeq uate peak bone mass. Since cutaneous synthesis of vitamin D is rather limited in winter, oral vitamin D supplementation should be considered .