oa Vitamin D and bone density in Qatari adults

It has been established that Vitamin D plays an active role in calcium homeostasis by regulating intestinal calcium and phosphorus absorption, renal calcium reabsorption and bone mineralization. Vitamin D deficiency has also been related to type 2 diabetes and metabolic syndrome.

Given that we have previously observed a very high rate of severe Vitamin D deficiency in Qatari girls the aim of this study was to examine whether Vitamin D deficiency was carried on into adulthood in a Qatari population and examine the effect upon bone mineral density and metabolic health status.

In this cross sectional study, we evaluated the serum 25 hydroxy-Vitamin D (25(OH)D) levels of 171 male and female Qatari adults (37.2 ± 10 years, body fat 44.1 ± 8.8 %, BMI 31.9 ± 7.9 kg/m²), bone mineral density (BMD) and body composition assessment with dual energy X-ray absorptiometry (DEXA). In addition, subjects were assessed for aerobic fitness. Haematological investigations included fasting, glucose, insulin, and lipid profile analysis.

Despite high level of body fatness and low aerobic fitness (Predicted VO²max 25.2 ± 7.2 ml/kg/min), blood pressure, glucose, insulin and lipid markers were all within acceptable ranges. Vitamin D deficiency was seen in this group with mean serum 25(OH)D being 15.8 ± 10.3 ng/ml, while PTH was just within the normal range (63.4 ± 23.8 pg/ml). Mean total body BMD was within the acceptable limits (1.2 ± 0.1 g/cm³). There was no correlation between 25(OH)D and BMD, however, BMD was strongly associated with total body weight (r=0.540, p<0.05) and BMI (r=0.456, p<0.05). Furthermore, there were no significant correlations between 25(OH)D and markers of type 2 diabetes, dyslipidaemia, or fitness.

The results suggest despite high levels of body fatness, low aerobic fitness and Vitamin D deficiency that this cohort were relatively healthy. On first impression, body weight appears to be a protective mechanism in maintaining BMD within this population. However, those individuals with a BMI < 25 kg/m² had normal BMD despite extremely low serum 25(OH)D levels (12.6 ± 7.6 ng/ml). This suggests that further research is warranted to elucidate possible contributing factors resulting in a normal BMD despite minimal sun exposure.