Omega-3 supplementation and non-alcoholic fatty liver disease: a systematic review and meta-analysis
Non-alcoholic fatty liver disease (NAFLD) is a frequent accompaniment of obesity and insulin resistance. With the prevalence approaching 85% in obese populations, new therapeutic approaches to manage NAFLD are warranted. A systematic search of the literature was conducted for studies pertaining to the effect of omega-3 polyunsaturated fatty acid (PUFA) supplementation on NAFLD in humans. Primary outcome measures were liver fat and liver function tests: alanine aminotransferase (ALT) and aspartate aminotransferase . Data were pooled and meta-analyses conducted using a random effects model. Nine eligible studies, involving 355 individuals given either omega-3 PUFA or control treatment were included. Beneficial changes in liver fat favoured PUFA treatment (effect size = −0.97, 95% CI: −0.58 to −1.35, p <0.001). A benefit of PUFA vs. control was also observed for AST (effect size = −0.97, 95% CI: −0.13 to −1.82, p = 0.02). There was a trend towards favouring PUFA treatment on ALT but this was not significant (effect size = −0.56, 95% CI: −1.16 to 0.03, p = 0.06). Sub-analyses of only randomised control trials (RCTs) showed a significant benefit for PUFA vs. control on liver fat (effect size = −0.96, 95% CI: −0.43 to −1.48, p <0.001), but not for ALT (p = 0.74) or AST (p = 0.28). There was significant heterogeneity between studies. The pooled data suggest that omega-3 PUFA supplementation may decrease liver fat, however, the optimal dose is currently not known. Well designed RCTs which quantify the magnitude of effect of omega-3 PUFA supplementation on liver fat are needed.