TUESDAY, Dec. 8, 2009 (HealthDay News) -- Having a few more cups of coffee and running that extra mile each day can reduce a man's risk of dying of prostate cancer, two studies indicate.
The case for coffee and physical activity as prostate cancer preventatives is far from proven, according to the research reported Tuesday at an American Association for Cancer Research meeting in Houston. But data from the Health Professionals Follow-Up Study show a clear association with both daily activities.
"I wouldn't recommend that people change their coffee-drinking habits based on this study," said Kathryn M. Wilson, a research fellow in epidemiology at the Harvard School of Public Health, and lead author of one report. "But if you like coffee, there is no compelling reason to cut back at this point."
Her data on the nearly 50,000 men in the study showed how common a diagnosis of prostate cancer has become since widespread screening began. In the 20 years from 1986 to 2006, 4,975 cases of prostate cancer were diagnosed, affecting just about 10 percent of the men in the study.
But only 846 of those cancers were life-threatening, because they had spread beyond the prostate gland or were growing aggressively, Wilson said. And while the study found just a weak relationship between consumption of six or more cups of coffee a day and a reduced risk of all forms of prostate cancer (down about 19 percent), the reduction for the aggressive form was much more marked -- 41 percent.
And there was a clear relationship between the amount of coffee consumed and prostate cancer risk, Wilson said: "The more coffee you drank, the more effect we saw."
The caffeine in coffee doesn't seem to be the link, since the same reduction was seen for consumption of decaffeinated coffee, she said. Instead, "it has something to do with insulin and glucose metabolism," Wilson said. "A number of studies have found that coffee is associated with a reduced risk of diabetes."
This study is just a starting point for establishing a relationship between coffee and prostate cancer, Wilson stressed. "At this point, we would just like to confirm whether it exists in different populations," she said. "We hope that this study drives more research so that we really know what is going on."
The other study, by Stacey A. Kenfield, a research associate at the Harvard School of Public Health, looked at the levels of physical activity among 2,686 men in the study who were diagnosed with prostate cancer. It found, as many other studies have, that exercise is good for overall health, with a 35 percent lower death rate for men who reported three or more hours a week of vigorous physical activity, such as jogging, biking, swimming or playing tennis.
And the death rate from prostate cancer, specifically, for men who exercised vigorously -- five or more hours per week -- was 56 percent lower than for those who did not.
"This is the first study to show an effect of physical activity not only on overall survival, but on prostate cancer survival," she said.
It's already well known how physical activity reduces overall mortality, Kenfield said. "It affects immune function and reduces inflammation, among the major processes involved. But it's not clear yet how it is related to prostate cancer and survival."
Details on prostate cancer are provided by the U.S. National Cancer Institute.