Serum 25-Hydroxyvitamin D in Obese Spanish Adults: the Camargo Cohort Study

To describe the 25(OH)D status in Spanish obese postmenopausal women and men ≥ 50 years, to compare their results with those of the overweight or normal weight population, and to determine whether differences are observed between both sexes and with seasonal variation throughout the year.

We studied 2597 subjects (1826 postmenopausal women and 771 men ≥ 50 years). Serum concentrations of 25(OH)D, intact parathyroid hormone (PTH), aminoterminal propeptide of type I collagen (PINP), and C-terminal telopeptide of type I collagen (CTX) were determined by electrochemiluminiscence (Elecsys 2010, Roche). Bone mineral density (BMD) was measured by DXA. Participants were divided according to body mass index (BMI) groups (normal ≥ 20 and < 25 kg/m², overweight ≥ 25 and < 30 kg/m², or obese ≥ 30 kg/m²).

Obese people had lower serum 25(OH)D values (20.9 ± 8.2 ng/ml) than overweight (23.3 ± 8.8 ng/ml; p < 0.0001) or normal-weight subjects (24.4 ± 8.9 ng/ml; p < 0.0001). They have also lower levels of both PINP and CTX. In contrast, PTH concentrations and BDM values were higher in obese individuals. When stratifying by sex, the difference in serum concentration of 25(OH)D remained significant in women, but not in men, persisted throughout the year, and was inversely correlated with BMI and waist circumference.

Despite lower serum 25(OH)D concentrations and higher PTH levels, obese and overweight women have higher lumbar spine and hip BMD and lower bone remodeling markers than normal weight women, suggesting that low serum 25(OH)D levels do not negatively affect bone health.