How does coffee prevent liver fibrosis? biological plausibility for recent epidemiological observations

Abstract

The published epidemiological data demonstrating an inverse relationship between coffee (and potentially other caffeinated beverage) consumption and liver fibrosis and its downstream complications are weighty and rapidly accumulating. Several excellent recent reviews examine this evidence in great detail (1–3), and the overwhelming conclusion is that this inverse relationship is real – coffee drinking reduces liver fibrosis. Among the strongest studies to support this observation are the findings that, after adjustment for confounders, individuals in the highest quintile of caffeine consumption had less than one third the risk of ALT elevation of those in the lowest quintile (odds ratio (OR) 0.31, 95% CI 0.16–0.61) (4) and, perhaps more importantly, advanced liver fibrosis from chronic liver diseases of various etiologies is associated with reduced coffee and total caffeine consumption (5) with one study showing that the odds of having cirrhosis decreased with increasing daily consumption of coffee in a step-wise manner from an OR of 0.47 (95% CI 0.20–1.10) for patients consuming 1 cup of coffee per day to an OR of 0.16 (95% CI 0.05–0.50) for patients consuming 4 cups per day, compared to lifetime abstainers as the reference (OR 1.0) (6). Demonstrating the clinical significance of coffee consumption, Freedman and colleagues found that among patients with advanced fibrosis, those who consumed no coffee had a risk of hepatic decompensation or hepatocellular carcinoma (HCC) of 11.1 per 100 patient-years compared to just 6.3 per 100 patient-years in those consuming ≥ 3 cups of coffee per day, with no beneficial effect seen with tea or other sources of caffeine (7). Coffee consumption has also been shown to be associated with a lower risk of fatty liver disease (8), metabolic syndrome (9), and ultimately hepatocellular carcinoma (10). As a clinician or scientist interested in the pathogenesis of liver fibrosis, one may very well ask whether these findings are of great value.