Vitamin D deficiency may be linked to the development of nonalcoholic fatty liver disease, according to a recent study.
Researchers performed a systematic review of 17 case-control and cross-sectional studies, assessing the association between nonalcoholic fatty liver disease (NAFLD) and serum levels of 25-hydroxy vitamin D (25[OH]D). Included studies were selected from PubMed and EMBASE databases and published before April 22, 2013, evaluated vitamin D levels among cases and controls, and were based in North America (six studies), Asia (four studies) and Europe or Israel (seven studies).
Most studies indicated that vitamin D deficiency was more prevalent among patients with NAFLD than controls. This association lost statistical significance after adjustment for confounders in two studies, and two studies indicated an inverse association between NAFLD, as indicated independently by ALT and vitamin D levels.
Investigators also conducted a pooled analysis including 11 studies, with nine assessing continuous vitamin D levels in 4,855 patients and 7,939 controls, and nine assessing categorical vitamin D in 5,202 patients and 8,520 controls.
Analysis of continuous vitamin D indicated that those with NAFLD had average 25(OH)D levels 0.36 ng/mL lower than controls (P<.01). Assessment of categorical vitamin D indicated that patients with NAFLD were 26% more likely than controls to be vitamin D-deficient (OR=1.26; 95% CI, 1.17-1.35). Deficiency was more prevalent and more severe among Western participants with NAFLD than Eastern patients. Results were not impacted by the exclusion of individual studies, and no evidence of publication bias was observed (P=.32).
“We have demonstrated that vitamin D deficiency is prevalent in NAFLD subjects, suggesting that vitamin D may play a role in the development of the disease,” the researchers concluded. “The anti-inflammatory and immune-modulatory properties of vitamin D provide plausible mechanisms by which vitamin D may impact on disease progression and severity in NAFLD.
“Future research should focus on investigating prospectively the association between vitamin D and NAFLD, as well as on randomized controlled trials of vitamin D supplementation in NAFLD subjects.”