The effects of fish oil plus vitamin D3 intervention on non-alcoholic fatty liver disease: a randomized controlled trial

Purpose: The present study aimed to investigate fish oil plus vitamin D3 (FO + D) supplementation on biomarkers of non-alcoholic fatty liver disease (NAFLD). Methods: In a 3-month randomized controlled trial, 111 subjects with NAFLD, aged 56.0 ± 15.9 y, were randomized into FO + D group (n = 37), fish oil group (FO, n = 37) or corn oil group (CO, n = 37). The subjects consumed the following capsules (3 g/day), which provided 2.34 g/day of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) + 1680 IU vitamin D3 (FO + D group), or 2.34 g/day of EPA + DHA (FO group), or 1.70 g/d linoleic acid (CO group). Results: Using multivariable-adjusted general linear model, there were significant net reductions in serum alanine aminotransferase (ALT), and triacylglycerol (TAG) and TNF-α levels in the FO + D and FO groups, compared with the control group (P < 0.05). The supplemental FO + D also showed significant reductions in insulin (− 1.58 ± 2.00 mU/L vs. − 0.63 ± 1.55 mU/L, P = 0.050) and IL-1β (− 6.92 ± 7.29 ng/L vs. 1.06 ± 5.83 ng/L, P < 0.001) in comparison with control group. Although there were no significant differences between FO + D and FO groups regarding biochemical parameters, supplemental FO + D showed decreases in ALT (from 26.2 ± 13.5 U/L to 21.4 ± 9.6 U/L, P = 0.007), aspartate aminotransferase (AST, from 22.5 ± 7.0 U/L to 20.2 ± 4.0 U/L, P = 0.029), HOMA-IR (from 3.69 ± 1.22 to 3.38 ± 1.10, P = 0.047), and TNF-α (from 0.43 ± 0.38 ng/L to 0.25 ± 0.42 ng/L, P < 0.001) levels following the intervention. Conclusion: The present study demonstrated that groups supplemented with FO + D and FO had similar beneficial effects on biomarkers of hepatocellular damage and plasma TAG levels in subjects with NAFLD, while in the FO + D group, there were some suggestive additional benefits compared with FO group on insulin levels and inflammation. Trial registration: ChiCTR1900024866.