A new report, published in the August edition of the journal Hepatology, boils down the findings from 10 studies on coffee and liver cancer.
The studies were reviewed by researchers including Francesca Bravi, ScD of the Istituto di Ricerche Farmacologiche "Mario Negri" in Milan, Italy.
Together, the studies included 2,260 people with liver cancer and nearly 240,000 people without liver cancer. Participants lived in Greece, Italy, or Japan.
Participants reported their coffee-drinking habits. The data show that coffee drinkers were 41% less likely to have been diagnosed with liver cancer than people who don't drink coffee.
For every daily cup of coffee people drank, their odds of having been diagnosed with liver cancer dropped by 23%, compared with people who never drink coffee.
People who drank a lot of coffee were 55% less likely to have been diagnosed with liver cancer than those who didn't drink any coffee.
What's a lot of coffee? That depends on which of the 10 studies you look at. Some of the studies defined high coffee consumption as three or more daily cups. Others set the bar lower, at more than one daily cup.
The fact that liver cancer was rarer among coffee drinkers a world apart -- in Greece, Italy, and Japan -- suggests that the coffee findings weren't a fluke or a local phenomenon, note Bravi and colleagues.
They speculate that coffee perks up liver enzymes and may cut cirrhosis and liver cancer.
But Bravi's team doesn't promise that drinking coffee will prevent liver cancer. They note that people with various digestive and liver diseases might choose not to drink coffee for reasons that aren't reflected in the data.
Whether or not coffee prevents liver cancer "remains open to discussion," write Bravi and colleagues.