Differences in vitamin D status and calcium metabolism in Saudi Arabian boys and girls aged 6 to 18 years: effects of age, gender, extent of veiling and physical activity with concomitant implications for bone health.

OBJECTIVE Few data exist looking at vitamin D status and bone health in school-aged boys and girls from Saudi Arabia. The present study aimed to determine the extent of poor vitamin D status in school boys and girls aged 6-18 years and to examine if there was any difference in status with age, physical activity and veiling and concomitant effects on bone. DESIGN Cross-sectional study. SETTING Jeddah, Kingdom of Saudi Arabia. SUBJECTS A total of 150 boys (7-16 years) and 150 girls (6-18 years) from local schools were divided into age categories: 6-9 years (elementary school); 10-12 years (secondary school); 13-14 years (middle years); 15-18 years (high school). RESULTS Vitamin D status was significantly lower in girls than boys in all age groups (P < 0.01), with the 15-18-year-old girls having the lowest level (22.0 (SD 9.4) nmol/l) in comparison to the 15-18-year-old boys (39.3 (SD 14.0) nmol/l) and the 6-9-year-old girls (41.2 (SD 9.3) nmol/l). Parathyroid hormone status was highest in the 15-18-year-old girls in comparison to boys of the same age. A total of 64 % of 15-18-year-old girls had 25-hydroxyvitamin D (25OHD) status <25 nmol/l in comparison to 31 % in the 13-14 years age category, 26 % in the 10-12 years category and 2.5 % in the 6-9 years category. No boys had 25OHD status <25 nmol/l. Fully veiled girls had lower 25OHD status than partly veiled or unveiled girls (P < 0.05). Low 25OHD and high parathyroid hormone was associated with lower bone mass in the 6-9 years and 13-14 years age groups (P < 0.05). CONCLUSIONS These data suggest significant hypovitaminosis D in older adolescent females, which is a cause for concern given that there is currently no public health policy for vitamin D in the Kingdom of Saudi Arabia.