Biosocial factors affecting vitamin D status of women of childbearing age in the United Arab Emirates

Low serum 35-OHD in female Arab subjects, which may predispose their infants to hypocalcaemia, has been suggested to be due to inadequate sunshine exposure, but may include other sociobiological factors. The effects of duration of sunshine exposure - weighted against the magnitude of clothing (UV exposure) and other sociobiological variables such as age, education and living accommodation - on serum 25-OHD and mineral status of 33 UAE national women of childbearing age were compared with those of 25 non-Gulf Arabs and seventeen Europeans. Serum concentrations of calcium, phosphorus, alkaline phosphatase and intact parathyroid hormone among the groups were not significantly different. The serum concentration of 25-OHD in UAE nationals was 8.6 ng/ml (4.5-17.4), mean ± 1 SD, and in non-Gulf Arabs 12.6 ng/ml (60-26.4); both these values were significantly lower (p = < 0.0001) than the 64.3 ng/ml (49-84.3) found in Europeans. Compared with Europeans, the UAE and non-Gulf Arabs in this study were younger, had fewer years of education and had significantly lower clothing and UV scores (p < 0.0001). Furthermore, there was a positive correlation (r = 0.59425) between serum 25-OHD and UV score, but not with length of exposure. After adjusting for other confounding variables, nationality, clothing and UV scores remained major determinants of serum 25-OHD (p < 0.0001). Therefore, limited skin exposure to sunlight appears to be an important determinant of vitamin D status in our subjects. Strategies to increase vitamin D stores should include vitamin D supplementation or advice on effective sunlight exposure.