L ast year, I talked about what's good and what's bad about caffeine, the number-one drug in America (see Daily Health News, August 17, 2004). One of the benefits: A study at the National Institute of Diabetes & Digestive & Kidney Diseases suggested that caffeine could help prevent liver damage. Now a new study carries this premise even further: Japanese researchers have found that regular coffee drinking is associated with a reduced risk for liver cancer.

The results were published in the February 16, 2005 issue of Journal of the National Cancer Institute.

A Cup of Joe a Day

Using the large-scale Japan Public Health Center-based prospective study, Manami Inoue, MD, and her colleagues at the National Cancer Center in Tokyo identified 250 men and 84 women newly diagnosed with a type of liver cancer. They analyzed these patients according to their coffee intake, gender, diet, lifestyle factors, incidence of hepatitis virus infection and previous history of liver disease.

Researchers discovered that...

• Men and women who drank coffee on a daily or almost daily basis were much less likely to develop liver cancer than those who never drank coffee. The risk in the almost-never drinkers was 547 cases per 100,000 people over a 10-year period, versus 214 cases per 100,000 daily drinkers.

• The likelihood of liver cancer declined according to the amount of coffee consumed, from those who drank none at highest risk to drinkers of five-plus cups daily at lowest risk.

• The association of more coffee with less cancer persisted even when other lifestyle considerations, such as gender, diet, lifestyle factors, incidence of hepatitis virus infection and previous history of liver disease, were factored in.

Caffeine? Antioxidants? Or Something Else?

How does coffee confer these benefits? Dr. Inoue says that it is impossible to say for sure, as coffee is rich in antioxidants as well as caffeine. (Decaffeinated coffee is rarely consumed in Japan.) Other as-yet unidentified substances in coffee also may be responsible, though Daily Health News contributing editor Andrew L. Rubman, ND, believes that the caffeine and the chlorogenic acid, a compound found in the coffee, are what's responsible.

The researchers did not find any association between green tea -- also a rich source of caffeine and commonly consumed in Japan -- and a reduced incidence of liver cancer. Dr. Inoue explains that this may be because coffee and green tea do not contain the same antioxidants. In several animal studies, coffee compounds such as chlorogenic acid have demonstrated a protective effect against liver cancer.

Love Your Liver

It is much too soon to recommend that people change their coffee-drinking habits, says Dr. Inoue, and they should certainly not do so on the basis of this study alone. Further research is necessary to determine exactly why coffee has this protective effect and whether the effect occurs in populations other than the one studied here.

In the meantime, no need to stop that early morning cup of coffee on account of your liver. The American Liver Foundation also has 50 other suggestions on protecting your liver at www.liverfoundation.org/db/articles/1021.

Sources

• Manami Inoue, MD, section head, epidemiology and prevention division, Research Center for Cancer Prevention and Screening, National Cancer Center, Tokyo, Japan.
• American Liver Foundation, www.liverfoundation.org