Association of polychlorinated biphenyls with vitamin D in female subjects

Polychlorinated biphenyls (PCBs) are known endocrine disrupters. A potentially causal association of PCBs with vitamin D has been reported. Higher body mass index (BMI) is associated with lower PCB levels whilst the strongest association of PCBs with BMI is in non-obese individuals. Therefore, this study examined the association of PCBs with vitamin D₃ (25(OH)D₃) and the active 1,25-dihydrovitamin D₃ (1,25(OH)₂D₃₎ in a cohort of non-obese women.

58 female participants (age 31.9 ± 4.6 years; BMI 25.7 ± 3.7 kg/m²) had seven indicator PCBs [PCB28, PCB52, PCB101, PCB118, PCB138, PCB153 and PCB180] measured using high resolution gas chromatography, with total PCB level calculated. 25(OH)D₃ and 1,25(OH)₂D₃ levels were determined by isotope-dilution liquid chromatography tandem mass spectrometry.

In this cohort, vitamin D₃ (25(OH)D₃) and 1,25(OH)₂D₃ levels were 50.7 ± 25.3 nmol/L and 0.05 ± 0.02 ng/ml, respectively. Of those, 28 had vitamin D deficiency [25(OH)D₃ level <20 ng/ml (<50nmol/)]. Total PCBs correlated positively with total group 25(OH)D₃ (r = 0.22, p = 0.04) as did PCB118 (r = 0.25, p = 0.03). Total PCBs did not correlate with total group 1,25(OH)₂D₃; however, PCB180 did correlate positively with 1,25(OH)₂D₃ (r = 0.34, p = 0.03) as did PCB153 (r = 0.33, p < 0.03), with PCB 28 correlating negatively (r = -0.29, p < 0.04). In the vitamin D deficient subgroup, total PCBs, PCB153 and PCB180 positively correlated with 25(OH)D₃ (p < 0.05). Multilinear regression analysis indicated all associations could be accounted for by BMI.

Though certain PCBs associated with 25(OH)D₃ and 1,25(OH)₂D₃, all associations could be accounted for by BMI. This study therefore indicates that the deleterious effects from PCB accumulation are not mediated by effects on 25(OH)D₃ or 1,25(OH)₂D₃.