Recent studies have reported lower serum 25-hydroxyvitamin D (S-25OHD) concentrations in obese subjects compared with normal weight individuals. However, differences in DBP or in free and bioavailable S-25(OH)D concentrations between obese and normal-weight persons are not so well studied. We compared 43 obese (35.7±4.3 kg/m2) and 144 normal-weight (22.5±1.6 kg/m2) women aged 37-47. Blood samples and data on vitamin D and calcium intake (from food and supplements) were collected as well as lifestyle habits. Comparisons between the normal-weight and obese subjects were made with ANCOVA. DBP concentrations were significantly higher in obese compared with normal-weight subjects: (388±89 mg/l and 358±88 mg/l, respectively; p=0.033). Total S-25(OH)D concentrations were 56.7±18.2 nmol/l in normal-weight subjects and 50.4±17.9 nmol/l in obese subjects; p=0.004.The concentration of calculated free 25OHD was lower in obese woman compared with normal-weight women (10.7±4.1 nmol/l and 12.6±4.3 nmol/l, respectively; p=0.002). Also the calculated bioavailable 25(OH)D (free+albumin bound) was lower in obese persons (p<0.001). Total vitamin D intake, S-PTH concentration and sunny holidays were used as covariates. S-PTH was higher in obese compared to normal weight subjects (65.1±29.9 and 54.0±23.5 ng/l, respectively; p=0.017).Total vitamin D intake was higher in normal-weight than in obese subjects (15 μg/day and 11 μg/day, respectively; p=0.012), which in both groups met the vitamin D recommendation in the Nordic European countries (10 μg/day). The observed associations between BMI and total- free-and bioavailable 25(OH)D, DBP and PTH suggests that obese individuals may differ in their vitamin D metabolism and may be at higher risk of having vitamin D deficiency.
Disclosure: The authors declared no competing interests.