Low serum vitamin D is independently associated with unexplained elevated ALT only among non-obese men in the general population

Introduction and Objectives: There are inconsistent findings on the association between human non-alcoholic fatty liver disease (NAFLD) and vitamin D, perhaps due to insufficient specificity for gender and obesity status. We aimed to assess whether serum levels of 25-hydroxyvitamin D are associated with unexplained elevated alanine aminotransferase (ALT) in general population across gender and body mass index (BMI) levels. Materials and methods: A cross-sectional analysis of a population-based cohort with a nationwide-distribution using electronic medical database. The population consisted of individuals aged 20–60 years who underwent blood tests for ALT and vitamin D. Results: A total of 82,553 subjects were included (32.5% men, mean age 43.91 ± 10.15 years). The prevalence of elevated ALT was higher among men and women with vitamin D insufficiency or deficiency, but in multivariate analysis, adjusting for: age, BMI, serum levels of glucose, total cholesterol, triglycerides, statin use and season, only the association among men remained significant for the vitamin D deficiency category (OR = 1.16, 95%CI 1.04–1.29, P = 0.010). Stratification by BMI revealed that only among normal weight and overweight men vitamin D deficiency was associated with elevated ALT (OR = 1.27, 95%CI 1.01–1.59, P = 0.041 and OR = 1.27, 95%CI 1.08–1.50, P = 0.003, respectively). No independent association was shown among women at all BMI categories. Conclusions: In a “real-life” general population, the association between vitamin D deficiency and unexplained elevated ALT is specific for non-obese men. The clinical significance of vitamin D for human NAFLD should be further elucidated with attention for a modifying effect of gender and adiposity.