They showed that a person's risk of alcohol-induced liver cirrhosis dropped by more than a fifth with every daily cup of coffee. But coffee did not reduce the risk of other types of cirrhosis.
The finding corroborates outcomes of smaller studies that highlighted an inverse relationship between coffee consumption and risk of cirrhosis attributed to alcohol.
The study of 125,580 adults compared the outcomes of a survey into alcohol and coffee consumption with rates of cirrhosis over 22 years of follow-up.
During this time, 330 cases of liver cirrhosis were detected, 199 of which were related to heavy alcohol consumption. The researchers found that with each additional daily cup of coffee, the risk of alcohol-associated cirrhosis fell by 22 per cent.
They also showed that levels of liver enzymes associated with hepatocellular damage were lower than expected among heavy drinkers if they also had a high coffee intake.
They assessed 37,620 people for aspartate aminotransferase (AST) and 69,904 for alanine aminotransferase (ALT), which are typically found at high levels in people with a history of heavy alcohol consumption.
Heavy alcohol drinkers were the most likely to have higher-than-average levels of these enzymes. But heavy drinkers who averaged four or more cups of coffee a day were half as likely to have elevated AST and ALT levels as those who drank one cup of coffee a day or less.
The findings suggest that coffee drinking may account for the variability in cirrhosis susceptibility among heavy drinkers, although how remains unclear.
Tea consumption had no effect on the risk of alcohol-associated liver cirrhosis, making it likely that a component of coffee other than caffeine is responsible.
Lead researcher Dr Arthur Klatsky, from Kaiser Permanente in California, said: 'There is no solid basis for explaining the apparent protection by coffee, nor can we say whether it is more likely an effect by caffeine or another coffee ingredient. The major thrust should be to try to determine the coffee component involved and how it works.'
Arch Intern Med 2006; 166: 1,190-5
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