Systematic Review and Meta-analysis: The Role of Diet in the Development of Nonalcoholic Fatty Liver Disease

BACKGROUND & AIMS: The association of nonalcoholic fatty liver disease (NAFLD) with dietary factors is well estab-lished but not thoroughly investigated. This systematic review and meta-analysis synthesizes available evidence regarding the effect of nutrition on the presence and severity of NAFLD. METHODS: A literature search was conducted identifying studies published between January 1985 and May 2021. We included studies with a dietary assessment and anthropometry based on validated tools, performed by a qualified dietitian or a trained health professional. We examined dif-ferences between patients with NAFLD and healthy controls as well as patients with NAFLD and nonalcoholic steatohepatitis (NASH). Risk of bias was assessed with the Risk Of Bias In Non-randomised Studies of Interventions (ROBINS-I) tool. RESULTS: There were 60 eligible studies with 100,621 patients. The risk of bias was moderate for the majority of studies (41/60; 68%). According to meta-analyses, total caloric intake was higher in patients with NAFLD compared with controls (mean difference, 78.08; 95% confidence interval, 41.03-115.13). Macronutrient (protein, fat, and carbohydrate) consumption as proportion of total caloric intake and daily intake of fiber, caffeine and vitamins E, A, and C did not signifi- cantly differ between patients with NAFLD and controls. Soft drink consumption had a trend towards association with the presence of NAFLD. However, the odds ratio was 4.4 and the confidence intervals very wide. Finally, there was no significant difference in any comparison between patients with NAFLD and NASH, although the number of patients was relatively small. All meta-analyses had significant heterogeneity. CONCLUSIONS: Overall, despite high heterogeneity among studies, this meta-analysis demonstrated that higher caloric intake is positively associated with NAFLD, whereas diet composition in macronutrients was not associated with the presence or severity of the disease.