Environmental Glyphosate Exposure Is Associated with Lower Serum 25-Hydroxyvitamin D Concentrations: A Cross-Sectional Analysis of NHANES 2013–2018

Glyphosate is an herbicide used to control plant growth and ripen specific crops. Glyphosate exposure has been associated with cancer, metabolic and neurological diseases, and reproductive issues in humans. A common element linking these disorders could be vitamin D deficiency. However, the relationship between glyphosate exposure and vitamin D status in the general population remains unclear. This analysis focused on the association between urinary glyphosate levels and serum 25-hydroxy vitamin D [25(OH)D] concentrations in a large representative sample of U.S. adults. Data from 4284 participants in the National Health and Nutrition Examination Survey (NHANES) between 2013–2018 were analyzed. Serum 25(OH)D levels were modeled using multivariable weighted linear regression, with adjustment for age, sex, race/ethnicity, body mass index, season, education, income, physical activity, smoking, and kidney function. Urinary glyphosate concentration was inversely associated with serum 25(OH)D in both the design-based univariate weighted analysis (β = −3.537, p = 0.035) and adjusted survey-weighted models for major confounding factors (β = −4.208, p = 0.009), using Taylor linearization for variance estimation to account for the complex NHANES survey design. In stratified analysis, the relationship between total vitamin D intake and serum 25(OH)D was found to be significantly modified by glyphosate exposure, with stronger dietary dependence observed in the high-exposure tertile (β = 12.88, p < 0.0066) than in the low-exposure tertile (β = 7.41, p < 0.0165). Higher urinary glyphosate concentration was associated with lower serum 25(OH)D levels in U.S. adults, suggesting it may represent an unrecognized risk factor for vitamin D deficiency. Longitudinal and experimental studies are needed to clarify causality, the underlying mechanisms, and public health implications.