Systematic review and meta-analysis: The role of diet in the development of non-alcoholic fatty liver disease

ABSTRACT Background The association of non-alcoholic fatty liver disease (NAFLD) with dietary factors is well established 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 differences between NAFLD patients and healthy controls as well as patients with NAFLD and non-alcoholic steatohepatitis (NASH). Risk of bias was assessed with the Robin-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 NAFLD patients compared to controls (MD=78.08, 95%CI:41.03-115.13). Macronutrient (protein, fat and carbohydrate) consumption as proportion of total caloric intake and daily intake of fibre and vitamins E, A and C did not significantly differ between 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, however 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, while diet composition in macronutrients was not associated with the presence or severity of disease.