The effects of low carbohydrate diets on liver function tests in nonalcoholic fatty liver disease: A systematic review and meta-analysis of clinical trials

Background: Although several observational and experimental studies have examined the effects of low carbohydrate diets (LCDs) on nonalcoholic fatty liver disease (NAFLD), there are considerable inconsistencies among studies. We summarized the effect of LCDs on liver function tests, including intrahepatic lipid content (IHLC), alanine transaminase (ALT), aspartate aminotransferases (AST), and gamma-glutamyl transferase (GGT) in patients with NAFLD. Materials and Methods: PubMed, ISI Web of Science, Scopus, and Google Scholar databases were searched for relevant publications until July 2014, resulting in ten relevant papers that were included in meta-analysis. Related articles were found by searching Medical Subject Heading terms of “NAFLD” in combination with “low carbohydrate.” For this meta-analysis, we used mean differences and standard errors of liver function biomarkers. Summary effect and corresponding confidence interval (CI) were estimated using random effect models. Heterogeneity between studies was assessed using Cochran’s Q- and I-squared tests. Results: Our search led to ten eligible papers that evaluated serum ALT levels (n = 238), nine reported serum AST levels (n = 216), five reported serum GGT concentrations (n = 91), and four assessed IHLC (n = 50). LCD decreased IHLC by −11.53% (95% CI: −18.10, −4.96; I² = 83.2%). However, the effect of LCD on liver enzymes was not significant. Mean differences for the effects of LCDs on ALT, AST, and GGT were −4.35 IU/L (95% CI: −12.91, 4.20; I² = 87.9%), −1.44 IU/L (95% CI: −4.98, 2.10; I² = 61.4%), and −7.85 IU/L (95% CI: −29.65, 13.96; I² = 99.4%), respectively. Conclusion: LCD consumption in subjects with NAFLD led to a significant reduction in IHLC, but did not significantly affect the concentration of liver enzymes.