Coffee May Lower Liver Cancer Risk
But true cause and effect haven't yet been proven, one expert says
THURSDAY, Aug. 2, 2007 (HealthDay News) -- People who drink coffee are 41 percent less likely to develop liver cancer compared with folks who don't indulge in the brew, Italian researchers report.
"Moreover, the apparent favorable effect of coffee drinking was found both in studies from southern Europe, where coffee is widely consumed, and from Japan, where coffee consumption is less frequent, and in subjects with chronic liver diseases," the researchers wrote in the August issue of Hepatology.
One expert said it's too early to laud coffee as an anti-cancer agent, however.
"I don't doubt that the association is true, but it is hard to know the cause," said Dr. Alfred I. Neugut, a professor of medicine and epidemiology at Columbia University College of Physicians and Surgeons and co-director of cancer prevention at New York Presbyterian Hospital in New York City. He was not involved in the study.
Without evidence of a real biological mechanism, the finding could be just a statistical artifact, Neugut said. "What's missing from the study is biological plausibility, so one has to have a degree of skepticism," Neugut said.
However, the findings aren't unique: In February, researchers at Japan's National Cancer Center tracked more than 90,000 older adults for 10 years and found that liver cancer rates fell by half in daily coffee drinkers, compared to people who did not consume the drink. That study was published in the Journal of the National Cancer Institute
More than 17,500 new cases of liver or bile duct cancer are diagnosed each year in the United States, according to the American Cancer Society.
In the new study, a team led by Dr. Francesca Bravi, of the Istituto di Ricerche Farmacologiche Mario Negri in Milan, reviewed 10 published studies on liver cancer that included information on how much coffee the patients drank.
They found a 41 percent reduction in the risk for liver cancer among coffee drinkers compared with those who never drank coffee.
Animal and laboratory studies have suggested that certain compounds in coffee may block enzymes involved in cancer detoxification, the Italian team noted. In addition, caffeine has been shown to have favorable effects on liver enzymes, they said, and coffee has also been linked to a lower risk of liver disease and cirrhosis, which can lead to liver cancer.
"Despite the consistency of these results, it is difficult to derive a causal inference on the basis of the observational studies alone," the authors noted.
"The results from this meta-analysis provide quantitative evidence of an inverse relation between coffee drinking and liver cancer," the Italian group concluded. "The interpretation of this association remains, however, unclear and the consequent inference on causality and worldwide public health implications is still open for discussion."
For more information on liver cancer, visit the American Cancer Society.