Feb. 15, 2005 -- There's more good news for the roughly 100 million Americans who couldn't imagine getting through the day without their coffee fix. Recent studies have shown that regular coffee consumption may lower the risk of developing diseases such as diabetes and Parkinson's. Now comes word that it may also protect against two common cancers.
Two separate studies, reported in the Feb. 16 issue of The Journal of the National Cancer Institute, examined the impact of coffee drinking on cancer risk.
Researchers in Japan found that regular coffee drinkers had about half the incidence of liver cancer as people who never drank coffee. And a study from the Harvard School of Public Health showed that drinking decaf, but not caffeinated, coffee appeared to have a similar impact on colorectal cancer risk.
Is Decaffeinated Coffee Really Best?
In the Harvard study, researchers examined data from two large, ongoing health trials involving 134,000 people. The participants were questioned about their coffee, tea, and caffeine consumption at different time periods over the course of 15 years.
Researcher Karin B. Michels, ScD, and colleagues found no association between consumption of caffeinated coffee or tea and colorectal cancer risk. But people who regularly drank two or more cups of decaffeinated coffee a day had about half the rate of rectal cancer as people who never drank decaffeinated coffee.
Michels tells WebMD that she initially thought the apparent protection could be explained by the fact that the decaffeinated coffee drinkers tended to have healthier lifestyles than the people who drank caffeinated coffee. But tea drinkers in the study also tended to have healthier habits, but had the same cancer risk as people who drank caffeinated coffee.
Even though she says now she believes that decaffeinated coffee may have unique cancer-fighting benefits, the researcher is not yet recommending that people switch from high-test to low.
"I would definitely like to see more studies that focus on decaffeinated coffee," she says.
Coffee and Liver Cancer
The second study, reported by researchers from Tokyo's National Cancer Center, involved 90,500 middle-aged and elderly men and women living in Japan. More than 300 of the participants developed liver cancer during a 10-year period.
The researchers reported that people who drank coffee every day or almost daily had about half the liver cancer risk as those who never drank coffee. The more coffee people drank the lower their risk. And the protective benefits appeared to extend to those with chronic hepatitis C and B infections. They are at very high risk for developing liver cancer.
The study did not distinguish between caffeinated and decaffeinated coffee consumption, because few Japanese people drink decaffeinated coffee.
Nutritional epidemiologist Nancy Potischman, PhD, tells WebMD that the fact that liver cancer is common in Japan adds strength to the findings. The cancer is relatively rare in the United States, with about 15,000 cases diagnosed annually.
She also found it compelling that the more coffee people drank the more they seemed to be protected from liver cancer.
"That is a good indication of a real effect and not just something that is seen by chance," she says. "As an epidemiologist I always want to see more evidence, but these findings are very compelling."