Coffee may help prevent a common type of liver cancer, suggests a Japanese study. Researchers studied 90,000 people and found that those who drank coffee daily or nearly every day had half the risk of liver cancer than those who never drank coffee. The protective effect occurred in people who drank one to two cups 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. The study appears in the Journal of the National Cancer Institute.