Plant-based diets, genetic predisposition and risk of non-alcoholic fatty liver disease

BACKGROUND: Diets rich in plant-based foods are associated with lower risks of non-alcoholic fatty liver disease (NAFLD), while the prospective evidence is limited. We aimed to examine longitudinal associations of plant-based diets and genetic susceptibility with NAFLD risk. METHODS: This longitudinal cohort study included 159,222 participants (58.0 ± 8.0 years old, 55.7% female) free of NAFLD in the UK Biobank. We calculated the overall plant-based diet index (PDI), the healthful plant-based diet index (hPDI), and the unhealthful plant-based diet index (uPDI). New-onset NAFLD was the primary outcome. The weighted polygenic risk score was calculated based on risk variants associated with NAFLD. Hazard ratios (HR) and 95% confidential intervals (CI) were estimated by Cox proportional hazards model. Magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) measured liver fat content in a subsample of 20,692 participants (57.5 ± 7.4 years old, 52.6% female) was the secondary outcome. The associations between plant-based diet indices and MRI-PDFF were evaluated using generalized linear models. RESULTS: During a median follow-up of 9.5 years, 1541 new-onset NAFLD cases were documented. Compared to the lowest quintile, multivariable-adjusted hazard ratios (HRs) of NAFLD in the highest quintile were 0.78 (95% confidential intervals [CI], 0.66–0.93, p-trend =0.02), 0.74 (95% CI, 0.62–0.87, p-trend <0.0001), and 1.24 (95% CI, 1.05–1.46, p-trend = 0.02) for overall PDI, hPDI, and uPDI, respectively. For liver fat content, higher overall PDI and hPDI were associated with lower MRI-PDFF, while higher uPDI was associated with higher liver fat content. We observed a significant interaction between hPDI and PRS (p-interaction =0.03), and the NAFLD risk was lowest among participants with the highest hPDI and low genetic risk. CONCLUSIONS: Higher intake of plant-based diets especially healthful plant-based diets was associated with lower NAFLD risk and liver fat content regardless of genetic susceptibility, whereas an unhealthful plant-based diet was associated with higher NAFLD risk and intrahepatic steatosis. These results suggest that the quality of plant-based foods should be highlighted when adopting a plant-based diet. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12916-023-03028-w.