The study, published in the Archives of Internal Medicine, shows that among more than 125,000 people studied for up to 22 years, coffee drinkers were less likely to be diagnosed with alcoholic cirrhosis.
"These data support the hypothesis that there is an ingredient in coffee that protects against cirrhosis, especially alcoholic cirrhosis," the researchers write.
But they aren't recommending that anyone rely on coffee to prevent alcoholic cirrhosis. Not drinking heavily is a better strategy for liver health, the researchers note.
They included Arthur Klatzky, MD. He works in the research division of Kaiser Permanente Medical Care Program of Oakland, Calif.
Coffee and Alcohol
Participants signed up for the study between 1978 and 1985. They were followed until the end of 2001.
Upon joining the study, participants got a checkup and completed surveys about their use of alcohol, coffee, tea, and cigarettes. None had already been diagnosed with liver problems.
Most participants noted drinking light or moderate amounts of alcohol (up to two daily drinks). Only 8% admitted drinking three or more alcoholic drinks per day.
Typical coffee consumption was one to three daily cups, noted by 42% of the group. Another 16% reported drinking four or more daily cups of coffee.
Alcoholic Cirrhosis Rarer
Over the years, 330 participants were diagnosed with cirrhosis; 199 of those cases were alcoholic cirrhosis. The remaining cases of cirrhosis were nonalcohol related.
For every daily cup of coffee that participants reported drinking, they were 22% less likely to have been diagnosed with alcoholic cirrhosis during the study, Klatzky's team reports.
The odds of developing nonalcoholic cirrhosis weren't linked to coffee consumption.
Participants only took the survey once -- when the study started. So the data don't include changes in coffee or alcohol consumption.
People don't always report their drinking habits accurately, note Klatzky and colleagues, adding that participants' alcohol use is "relatively stable."
Was It the Caffeine?
Klatzky's team didn't identify what ingredient in coffee might help protect the liver from alcoholic cirrhosis.
Past studies on caffeine and alcoholic cirrhosis haven't reached any firm conclusions, note Klatzky and colleagues. "In our opinion this issue is quite unresolved," they write, adding that coffee drinkers were more common than tea drinkers in their study.
As an observational study, the study doesn't prove that drinking coffee cuts the chance of developing alcoholic cirrhoses, the researchers caution. They also point out that if coffee protects the liver, the effects of adding cream, milk, sugar, or other substances to coffee aren't yet known.