Vitamin D status of apparently healthy schoolgirls from two different socioeconomic strata in Delhi: relation to nutrition and lifestyle.

Forty to fifty per cent of skeletal mass, accumulated during childhood and adolescence, is influenced by sunlight exposure, physical activity, lifestyle, endocrine status, nutrition and gender. In view of scarce data on association of nutrition and lifestyle with hypovitaminosis D in Indian children and adolescents, an in-depth study on 3,127 apparently healthy Delhi schoolgirls (6-18 years) from the lower (LSES, n 1,477) and upper socioeconomic strata (USES, n 1650) was carried out. These girls were subjected to anthropometry and clinical examination for hypovitaminosis D. Girls randomly selected from the two strata (LSES, n 193; USES, n 211) underwent detailed lifestyle, dietary, biochemical and hormonal assessment. Clinical vitamin D deficiency was noted in 11.5 % girls (12.4 % LSES, 10.7 % USES). USES girls had significantly higher BMI than LSES counterparts. Prevalence of biochemical hypovitaminosis D (serum 25-hydroxyvitamin D < 50 nmol/l) was seen in 90.8 % of girls (89.6 % LSES, 91.9 % USES, NS). Mean intake of energy, protein, fat, Ca, vitamin D and milk/milk products was significantly higher in USES than LSES girls. Conversely, carbohydrate, fibre, phytate and cereal intakes were higher in LSES than USES girls. Physical activity and time spent outdoors was significantly higher in LSES girls (92.8 v. 64 %, P = 0.000). Significant correlation between serum 25-hydroxyvitamin D and estimated sun exposure (r 0.185, P = 0.001) and percentage body surface area exposed (r 0.146, P = 0.004) suggests that these lifestyle-related factors may contribute significantly to the vitamin D status of the apparently healthy schoolgirls. Hence, in the absence of vitamin D fortification of foods, diet alone appears to have an insignificant role.