Abstract
There is growing evidence that females in the Middle East are not obtaining sufficient amounts of vitamin D, the perceived reason being their unhealthy lifestyle. This situation is a cause for concern particularly for adolescent females, because adequate vitamin D status has been shown to promote bone mineral accrual in adolescence. Achieving a high peak bone mass (PBM) may help decrease the risk of postmenopausal osteoporosis and fragility fractures. The aim of this study was to assess the vitamin D status among Kuwaiti adolescent girls and to assess its impact and those of lifestyle, on their bone mass. A total of 233 adolescent females (mean age 15. 4 +/- 1. 67 y) were enrolled in the study. Fasting blood samples were assayed for vitamin D status (ie, 25(OH)D), parathyroid hormone (PTH) and adjusted serum calcium. Lumbar spine-bone mineral content (LS-BMC) (L1-L4) was measured using dual-energy x-ray absorptiometry (DXA) (Hologic, QDR 4500). Anthropometric measurements and skin colour-type were determined by standard methods. Food intake was assessed by a food frequency questionnaire. Duration of sunshine exposure, mode of dress and physical activity level were also obtained in standard questionnaires. Results showed that mean +/- SD 25(OH)D was 21. 4 +/- 7. 39 nmol/L, whereas that of PTH was 9. 8 +/- 13. 54 pmol/L, and mean adjusted serum calcium was 2. 29 +/- 0. 11 mmol/L. None of the girls had an adequate vitamin D status (serum 25(OH)D <75 nmol/L), 89. 3 % had levels below 30 nmol/L and 52. 8 % had levels below 20 nmol/L. Mean +/- SD LS-BMC was 47. 5 +/- 9. 7 g. Only 33 % of the girls consumed milk or sour milk daily, whereas 45 % of the girls consumed carbonated drinks daily. Only 15 % of the total girls were engaged in physical activity. Milk intake was the only predictor of vitamin D status in both seasons (adjusted r2=0. 016, p=0. 032). Those who consumed milk less than 1 time/week had a mean +/-SD 25(OH)D of 19. 7 +/- 6. 5 nmol/L compared to those who consumed milk 1-2 times a week (21. 3 +/- 5. 5 nmol/L). Those who consumed milk more than 3 times a week had the highest level of 25(OH)D (22. 7 +/- 8. 6 nmol/L). Predictors of LS-BMC were puberty, body size and PTH {adjusted r2= 0. 555, p<0. 001). Milk intake contributed non-significantly to 1. 2 % of the variation in LS-BMC, whereas, meat intake contributed negatively to 4. 3 % of the variation (p=0. 007). Weight bearing activity contributed to 1. 5 % of the variation in LS-BMC. Those who were physically active had LS-BMC of 51. 8 +/- 8. 18 g vs. 46. 58 +/- 9. 8 g among those who were inactive (p=0. 06). The Kuwaiti adolescent girls were found to have a lower LS-BMC compared to their Lebanese, British and Caucasian Canadian counterparts. Given their vitamin D deficiency, hyperparathyroidism, relatively low LS-BMC, inactive lifestyle and unhealthy eating habits, the Kuwaiti adolescent girls may face an increased risk for developing osteoporosis at an early stage in life. There is an urgent need for population-based health strategies to: (1) raise awareness on the significance of vitamin D to general health; (2) stimulate a healthier lifestyle, especially among adolescent girls.