The researchers found that coffee seems to be connected to lower blood levels of gamma-glutamyltransferase -- known as GGT -- a liver enzyme involved in the secretion and absorption of bile that has been linked to liver cancer.

Residents of Finland drink more coffee per capita than Japanese, Americans, Italians and other Europeans, so researchers studied 60,323 Finnish participants ages 25 to 74 who were cancer-free at baseline. The Finns were included in seven independent cross-sectional population surveys conducted between 1972 and 2002 and followed up through June 2006.

The participants were surveyed on their coffee consumption and other dietary habits. Data on subsequent cancer diagnoses was collected from the country-wide Finnish Cancer Registry.

The study, published in the July issue of Hepatology, reported a significant inverse association between coffee drinking and the risk of primary liver cancer. The researchers found that the multi-variable hazards ratio of liver cancer dropped for each group that drank more coffee.

"The biological mechanisms behind the association of coffee consumption with the risk of liver cancer are not known," the authors said in a statement.