Data from an intervention study of ten NAFLD patients in which ethanol was measured in the portal vein blood of patients infused with a selective alcohol dehydrogenase inhibitor before a mixed meal test was performed showed that the first-pass effect obscures the level of endogenous ethanol production, suggesting that microbial ethanol could be considered to be involved in the pathogenesis of NAFLD. The gene discussed is AKR1A1; the disease is metabolic dysfunction-associated steatotic liver disease.