Association between serum vitamin D levels and metabolic dysfunction-associated steatotic liver disease: a cross-sectional study based on NHANES 2021-2023.

Background: Metabolic dysfunction-associated steatotic liver disease (MASLD) is a growing global health concern, and emerging evidence suggests a potential role of vitamin D in its pathogenesis. This study aims to evaluate the impact of serum vitamin D levels on the risk of MASLD using National Health and Nutrition Examination Survey (NHANES) data. Methods: We analyzed data from 3249 US adults based on NHANES 2021-2023 cycle. MASLD was defined by controlled attenuation parameter value ≥248 dB/m. Three multivariable logistic regression models were constructed: Model 1 (vitamin D alone), Model 2 (partially adjusted), and Model 3 (fully adjusted for demographic, metabolic, and inflammatory factors). Model performance was assessed using receiver operating characteristic analysis, calibration curves, and decision curve analysis (DCA). The mediation analysis was used to explore these associations. Results: The analysis revealed that the MASLD group had significantly lower median vitamin D levels (77.35 vs. 82.10 nmol/L, Conclusions: Our findings suggest that higher vitamin D levels were associated with lower odds of MASLD, highlighting its potential as a modifiable risk factor and a promising therapeutic target.