Vitamin D status in female students and its relation to calcium metabolism markers, lifestyles, and polymorphism in vitamin D receptor.

BACKGROUND Vitamin D is essential for maintiiining bone health and growth throughout life. Vitamin D deficiency not only leads to bone metabolic diseases in children and adults but may increase the risk of many chronic diseases. The aim of this study was to evaluate the prevalence of vitamin D deficiency and its relation with vitamin D receptor (VDR) gene polymorphism. In addition the study included the evaluation of known risk factors and their correlation to the vitamin D status among girls aged 11 - 17 years in Rafsanjan during the winter of 2009. METHODS In a cross-sectional study, 250 healthy female students (age range, 11 - 17 years) were selected by random sampling method. Fasting blood samples were collected and the concentration of serum 25 (OH) vitamin D3, PTH, ionized Ca, P, ALP, and VDR gene polymorphism (exon 9) were evaluated. Values of 20 nmol/L were considered severe, 20.1 - 37.5 nmol/L moderate, 37.6 - 50 nmol/L mild deficiency, and 25 (OH) vitamin D3 levels higher than 50 nmol/L were considered normal. RESULTS The results showed 59.6% of students suffered from vitamin D deficiency (14.4% severe, 24.4% moderate, and 20.8% mild deficiency). There was a significant relationship between serum levels of vitamin D with ionized Ca, PTH, ALP, type of clothing, and egg consumption, while no significant relationship was found between serum levels of vitamin D with age, residency, menstruation status, skin color, sun light exposure, body mass index, waist to hip ratio, exercise, physical activity, fish consumption, and polymorphisms in exon 9 of VDR gene. CONCLUSIONS This study indicated a high prevalence of vitamin D deficiency in female students in a sunny city, Rafsanjan in winter. Low sun light exposure, coverage especially veil, and low intake vitamin D are important factors in vitamin D deficiency in studied subjects.