Association between vitamin D and non-alcoholic fatty liver disease/non-alcoholic steatohepatitis: results from a meta-analysis.

Abstract

The prevalence and impact of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) have continued to increase in recent years. Previous reports have shown that hypovitaminosis D is associated with the prevalence and severity of non-alcoholic fatty liver disease (NAFLD). The aim of this study was to systematically evaluate the association of vitamin D levels, as measured by serum 25-hydroxy vitamin D [25(OH)D], with NAFLD and NASH. We searched all of the publications that assessed the association between vitamin D and NAFLD/NASH in the PubMed and EMBASE databases up to November 2014. In total, twenty-nine articles met the eligibility criteria, including twenty-seven studies about NAFLD and four studies about NASH, which were identified and included in the meta-analysis. Twenty-nine cross-sectional and case-control studies evaluated the association between vitamin D and NAFLD/NASH. Twenty-three studies provided data for a quantitative meta-analysis. Compared with the controls, the NAFLD patients had significantly lower levels of 25(OH)D (SMD-0.76; 95% CI-0.97 to-0.54) and were 1.26 times more likely to be vitamin D deficient (OR 1.26, 95% CI: 1.15 to 1.38). Compared with the controls, the NASH patients had significantly lower levels of 25(OH)D (SMD-1.30; 95% CI-2.37 to -0.23). Although the cross-sectional studies did not allow us to determine a causal nexus, our meta-analysis found lower serum 25(OH)D levels in NAFLD/NASH patients than in subjects without NAFLD/NASH, which suggests that hypovitaminosis D could play a role in the pathogenesis of NAFLD/NASH. Further studies are required to establish the causality between vitamin D status and NAFLD.