Interaction Between Alcohol Use and Metabolic Risk Factors for Liver Disease: A Critical Review of Epidemiological Studies

Coexistence of alcohol use and metabolic risk—the 2 commonest population risk factors for nonviral chronic liver disease—is a growing concern. Clinical evidence and mechanistic evidence point to considerable supraadditive interaction effects for the development and progression of chronic liver disease between hazardous alcohol use and metabolic abnormalities including obesity, diabetes, and the metabolic syndrome (MetS). Intermittent binge drinking once monthly or more often seems to be associated with progression of liver disease even when average alcohol intake is within the currently allowed limits for a diagnosis of nonalcoholic fatty liver disease (NAFLD), and supraadditive interaction between binge drinking and the MetS has been reported. There are contradictory findings regarding the association between low alcohol use and liver steatosis, but, clearly, the mechanisms of alcoholic hepatotoxicity extend beyond simple fat accumulation. The presence of liver steatosis seems to amplify alcoholic hepatotoxicity. Recent longitudinal studies of NAFLD subjects report low alcohol use associated with both increased fibrosis progression and an elevated risk for liver cancer and severe liver disease. There is no clear safe limit of alcohol intake in the presence of NAFLD or metabolic risk. The interaction effects between alcohol and metabolic dysfunction merit increased attention in public health policy, individual counseling, and risk stratification. Based on current evidence, a strict dichotomization of liver disease into either pure alcoholic or nonalcoholic may be inappropriate.