WASHINGTON – That hot cup of coffee may do more than just provide a tasty energy boost. It also may help prevent the most common type of liver cancer. A study of more than 90,000 Japanese found that people who drank coffee daily or nearly every day had half the liver cancer risk of those who never drank coffee.

The American Cancer Society estimates that 18,920 new cases of liver cancer were diagnosed in America last year and some 14,270 people died of the illness. Causes include hepatitis, cirrhosis, excess alcohol consumption, and diseases causing chronic inflammation of the liver.

Animal studies have suggested a protective association of coffee with liver cancer, so the research team led by Monami Inoue of the National Cancer Center in Tokyo analyzed a 10-year public health study to determine coffee use by people diagnosed with liver cancer and people who did not have cancer.

They found the likely occurrence of liver cancer in people who never or almost never drank coffee was 547.2 cases per 100,000 people over 10 years.

But among people who drank coffee daily there were 214.6 cases per 100,000, the researchers report in this week’s issue of the Journal of the National Cancer Institute.

They found that the protective effect occurred in people who drank one to two cups of coffee a day and increased at three to four cups. They were unable to compare the effect of regular and decaffeinated coffee, however, because decaf is rarely consumed in Japan.

Some studies have suggested caffeine aggravates symptoms of menopause or intensifies the side effects of some antibiotics. But studies have also shown that a skin cream spiked with caffeine lowers the risk of skin cancer in mice.