Urinary phthalate metabolite and bisphenol-A concentrations in association with serum vitamin D levels: results from pregnant and non-pregnant women in two US populations

Abstract

INTRODUCTION:Vitamin D, a fat-soluble prohormone, plays an essential role in bone metabolism and has been linked to numerous chronic diseases. In pregnant women, low levels of vitamin D are associated with a variety pregnancy complications including gestational diabetes and preeclampsia. Recent research suggests that certain endocrine-disrupting chemicals may alter vitamin D levels in adult men and women. To date, no epidemiology studies have investigated the extent to which exposure to phthalates or bisphenol A (BPA) are associated with circulating levels of vitamin D. Herein, we explored the relationships between urinary concentrations of phthalate metabolites and BPA and serum 25-hydroxyvitamin D (25(OH)D) in a representative sample of U.S. adult women. We also investigated these relationships, using repeated measures of biomarkers, in a nested-case control study of pregnant women in Boston, MA. METHODS: We analyzed biomarker data and relevant covariates collected from 3,974 adult women aged ≥ 20 years in the National Health and Nutrition Examination Survey (NHANES), 2001-2010. In a separate analysis, we examined repeated measures associations between urinary exposure biomarkers and serum vitamin D, collected at median 10 and 26 weeks of gestation, among 278 pregnant women. RESULTS: Among NHANES participants, urinary di(2-ethylhexyl) phthalate (DEHP) metabolites and BPA were inversely related to serum vitamin D, with significant associations detected among women of reproductive age (20-39 years old). In a separate repeated measures analysis among pregnant women, urinary phthalate metabolites and BPA were largely inversely associated with vitamin D. Stratifying by study visit showed significant associations for DEHP metabolites at 26 weeks (β for molar sum of DEHP metabolites=-0.92, p=0.02). Conclusions: These results suggest that environmental exposure to phthalates and BPA are associated with vitamin D levels in pregnant and non-pregnant women in the U.S.