Many patients with non-alcoholic fatty liver disease (NAFLD) also have low vitamin D levels. In fact, a recent meta-analysis found that NAFLD patients were 26% more likely to be vitamin D deficient compared with control subjects.
When corrected, levels of 25-hydroxy vitamin D >25 ng/mL have been associated with a 43% lower risk of type 2 diabetes mellitus compared with levels <14 ng/mL. Additionally, vitamin D supplementation has been shown to improve insulin resistance modestly versus placebo.
A review article in the February 2015 issue of the World Journal of Gastroenterology indicated that low vitamin D levels are closely linked to and potentially causative of NAFLD. The authors, who are affiliated with the University of Maryland School of Medicine in Baltimore and Medstar Washington Hospital Center in Washington, DC, summarized vitamin D’s role in NAFLD as follows:
· Vitamin D may improve insulin secretion and decrease insulin resistance.
· Vitamin D appears to reduce adipose tissue inflammation.
· Vitamin D has been linked to less hepatic inflammation.
· Vitamin D down-regulates hepatic fibrosis.
These are potential mechanisms through which vitamin D may alter NAFLD’s progression from a relatively benign precursor condition to fibrosis and steatosis.
Current clinical evidence suggests that vitamin D may prevent NAFLD’s progression. One study even indicated that patients treated with vitamin D supplementation experienced a significant decrease in markers of inflammation.
Still, clinical trials that evaluate the direct effect of vitamin D supplementation on NAFLD are needed. Until those studies are completed, vitamin D supplementation is not formally recommended for NAFLD patients, but it appears promising.