"For heavy drinkers, the more coffee they drank, they less likely they were to get the diagnosis of cirrhosis," said Dr. Arthur Klatsky, an investigator with Kaiser's Division of Research and lead author of the study.
Researchers followed more than 125,000 Northern California Kaiser members between 1978 and 1985. Participants, none of whom had liver disease at the outset, filled out a questionnaire that included their alcohol, coffee and tea-drinking habits.
By the end of 2001, 330 participants had been diagnosed with liver disease, and of those, 199 had alcohol-related cirrhosis.
Those who drank one cup of coffee per day were on average 20 percent less likely to have cirrhosis, despite heavy drinking. Drinking two to four cups of coffee reduced risk by 40 percent.
The Kaiser members who drank four or more cups of coffee per day cut their risk of developing liver cirrhosis by an astonishing 80 percent, according to the study, published in the Archives of Internal Medicine.
Tea drinking did not reduce risk of developing the liver disease, and those whodeveloped cirrhosis for reasons other than heavy alcohol consumption saw no protective benefits from drinking coffee, researchers found.
It is unclear whether it is the caffeine or something else in coffee that protects the liver from alcohol-induced damage. The researchers did not ask participants whether they drank caffeinated or decaffeinated coffee.
Cirrhosis results in progressive damage and impaired function of the liver. Causes include heavy and chronic alcohol drinking typically three or more drinks per day over a period of years and viruses, such as hepatitis.
More than 5 million people nationwide have cirrhosis, and nearly 28,000 die of chronic liver disease each year, according to the National Center for Health Statistics.
About a quarter of all heavy, chronic drinkers develop cirrhosis of the liver, and it is not known why some escape the disease, Klatsky said.
"The first message is this may be some clue as to why some people who drink a lot of alcohol get cirrhosis and some don't," Klatsky said.
Liver cells leak certain enzymes when they are damaged. A high level of these enzymes indicate cirrhosis.
Kaiser researchers first reported the protective qualities of coffee and cirrhosis in 1993 in a much smaller study. The two Kaiser studies and others suggest that coffee somehow protects the liver so it does not secrete these enzymes.
While researchers noted that people do not always tell the truth on questionnaires, "it seems unlikely that underreporting of alcohol intake is the entire explanation" for the findings, they wrote in the study.
The take-home message is not that people can Irish up their coffee with no ill effects, Klatsky warned.
But coffee by itself is not such a bad thing in this case.
"A person concerned about their liver certainly doesn't have to cut out coffee," Klatsky said. "In general, coffee gets a bad rap."
Contact Rebecca Vesely at firstname.lastname@example.org.