The more coffee a person drinks, the lower their risk of developing liver cancer, suggests a large study.

University of Helsinki researchers found that coffee seems to be connected to lower blood levels of gamma-glutamyltransferase (GGT), a liver enzyme involved in the secretion and absorption of bile that has been linked to liver cancer.

The researchers studied 60,323 Finnish participants aged 25 to 74 — all had no cancer at the start of the study — in seven surveys between 1972 and 2002. Participants were tracked until June 2006.

People who participated in the study had to complete questionnaires about their medical history, diet and lifestyle, and income.

They were also asked how many cups of coffee they drank a day and divided into groups based on those findings. The groups were broken into 0-1 cup, 2-3 cups, 4-5 cups, 6-7 cups and eight or more cups per day.

After an average period of follow-up of 19.3 years, 128 people involved in the study were diagnosed with liver cancer.

Researchers found that in the groups that drank the most coffee, the risk of developing liver cancer was the lowest, and that the risk was highest in those who drank less than two cups of coffee per day.

Those who had high blood levels of GGT and drank the least amount of coffee daily had the highest risk of liver cancer.

The reasons behind the seemingly protective role of coffee are unclear. "The biological mechanisms behind the association of coffee consumption with the risk of liver cancer are not known," the authors write. They caution that the findings do not prove excessive coffee drinking staves off liver cancer.

The study is to be published in the July issue of the journal Hepatology.