Effect of Vitamin D Supplement on Nonalcoholic Fatty Liver: A Systematic Review on Randomized Clinical Trials

Fatty liver is a common metabolic disorder that results in abnormal liver function due to the excessive accumulation of fat in the liver cells. Vitamin D can play a role in the improvement of fatty liver symptoms due to its anti-inflammatory, anti-fibrotic, and insulin-sensitizing roles. In this regard, the present study aimed to summarize the data obtained from clinical trials on the effect of vitamin D supplement on various parameters associated with nonalcoholic fatty liver disease.

Published studies during 1990 and 2018 were extracted through searching the scientific databases, including PubMed, Google Scholar, ScienceDirect, Scopus, and Web of Science, using the keywords of NAFLD, Nonalcoholic Fatty Liver Disease, Nonalcoholic Steatohepatitis, Vitamin D, Cholecalciferol, 1, 25 (OH) 2D3, and Calcitriol.

It seems that Vitamin D can improve the symptoms of nonalcoholic fatty liver disease by decreasing the fat content of the liver, levels of alanine transaminase and aspartate transaminase enzymes, preinflammatory cytokines, such as nuclear factor kappa-light-chain-enhancer of activated B cells and tumor necrosis factor-α, and level of a highsensitivity C-reactive protein as an inflammatory factor. In addition, vitamin D can positively affect the symptoms of nonalcoholic fatty liver disease through the improvement of insulin resistance. It can also have positive effects on oxidative stress by the reduction of the level of malondialdehyde and increase of antioxidant capacity.

Vitamin D can play an important role in the prevention and improvement of nonalcoholic fatty liver through various mechanisms.