Nigella sativa supplementation and non-alcoholic fatty liver disease: A systematic review of clinical trials

OBJECTIVE: Based on the results of previous studies, the effects of N. sativa on some of the non-alcoholic fatty liver disease's (NAFLD) biomarkers were positive; however, there were conflicting results regarding other variables. Therefore, the present systematic review of clinical trials was designed to clarify whether N. sativa effectively prevents the progression of NAFLD. MATERIALS AND METHODS: A search of four databases (Scopus, PubMed, Medline, and Google scholar) was conducted to identify the clinical trials that assessed the effects of N. sativa supplementation on NAFLD. The outcome variables of interest were biomarkers of hepatic steatosis, liver enzymes, insulin resistance, and inflammation. RESULTS: Overall, four randomized clinical trials (RCTs) were included. In three studies, hepatic steatosis grade decreased significantly after N. sativa supplementation. Serum levels of liver enzymes reduced significantly in three of four included trials. In the only study that examined the effect of N. sativa on insulin resistance parameters, all variables related to this factor were significantly reduced. In two included studies that measured biomarkers of inflammation, the serum levels of tumor necrosis factor α (TNF-α), high-sensitive C-reactive protein (hs-CRP), and interleukin 6 (IL-6) decreased significantly after intaking N. sativa supplements. CONCLUSION: Although the efficacy of N. sativa on liver enzymes and the grade of hepatic steatosis was reported in some of the included studies, more well-designed clinical trials are needed to determine the definitive effects of N. sativa on NAFLD. The present study provides suggestions that help to design future studies in this field.