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 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.
This research does provide a clue that coffee drinking might reduce the likelihood of a man being diagnosed with a more advanced prostate cancer, although there is still more research to do to confirm this and to uncover which component of coffee could be responsible.
The researchers do not recommend that men cultivate a heavy coffee drinking habit on the back of this research, not least because a high caffeine intake can cause other health problems.
"But if you like coffee, there is no compelling reason to cut back at this point" adds Kathryn M. Wilson, a research fellow in epidemiology at the Harvard School of Public Health, and lead author of one report.
The researchers documented the regular and decaffeinated coffee intake of nearly 50,000 men every four 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*. They also examined the cross-sectional association between coffee consumption and levels of circulating hormones in blood samples collected from a subset of men in the cohort.
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 same reduction was seen for consumption of decaffeinated coffee, ruling out a link to caffeine in coffee.
Instead, "it has something to do with insulin and glucose metabolism," Wilson said. "A number of studies have found that coffee has effects on insulin and glucose metabolism as well as sex hormone levels, all of which play a role in prostate cancer. It was plausible that there may be an association between coffee and prostate cancer.
This association might also help understand the biology of prostate cancer and possible chemoprevention measures.
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 for men who exercised vigorously was 12 percent lower than for those who didn't -- a figure that did not quite reach the level of statistical significance because the numbers were small, Kenfield explained.
Nevertheless, "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."
* CLICK HERE for the American Cancer Society’s Revised Prostate Cancer Screening Guidelines: What Has--and Hasn't--Changed
Materials for this write-up were sourced from the websites of the American Association for Cancer Research, Reuters and MedlinePlus