For those who get their health guidance from the nightly news on television, this week’s health tip from Diane Sawyer (ABC), Katie Couric (CBS), and Brian Willams (NBC) was that drinking coffee — and even decaffeinated coffee at that — could prevent prostate cancer.
This piece of wisdom is being derived from yet another analysis of data collected as part of the Health Professionals Follow-up Study, which has been tracking data from nearly 48,000 men employed as health professionals since 1986. The data in question were reported by Wilson et al. in the on-line version of the Journal of the National Cancer Institute.
According to the abstract of the paper by Wilson et al.:
- The analysis is based on only 5,035/47,911 patients (10.5 percent) who were actually diagnosed with prostate cancer, of whom 642/47,911 patients (1.3 percent) got fatal or metastatic prostate cancer.
- The average coffee intake of participants in 1986 was 1.9 cups per day.
- Compared to men who did not drink coffee at all, the men who drank ≥ 6 cups of coffee per day had
- A lower adjusted relative risk (ARR = 0.82) for a diagnosis of prostate cancer.
- A much lower ARR (of 0.40) for lethal prostate cancer .
- Drinking coffee was not associated with risk for diagnosis with localized or low-grade cancers.
- Drinking coffee was only weakly inversely associated with risk for high-grade cancer.
- The inverse association with lethal cancer was similar for regular and decaffeinated coffee.
- The age-adjusted incidence rates of all prostate cancers were
- 425/100,000 person-years for men who drank ≥6 cups of coffee per day
- 519/100,000 person-years for men who drank no coffee at all
- The age-adjusted rates of fatal or metastatic prostate cancer were
- 34/100,000 person-years for men who drank ≥6 cups of coffee per day
- 79/100,000 person-years for men who drank no coffee at all
The most insightful statement we have seen about this study to date comes from Ian Thompson, the lead investigator for the Prostate Cancer Prevention Trial and a professor in the Department of Urology at the University of Texas Health Science Center at San Antonio, who is quoted on Bloomberg.com as saying, “The wrong take-home message is ‘Drink more coffee and you won’t get prostate cancer.’ ”
There are numerous possible reasons for a finding like this … and it is very certainly possible that something in coffee (or perhaps even something in certain types of the instant coffee that many people drink) has a protective effect against prostate cancer. To quote Dr. Thompson again, “It’s an interesting observation. The proper result for this would be for folks in the drug discovery business to look at coffee to see if there may be something [that could be used as a drug to prevent prostate cancer].”
We have all previously been seduced by the idea that selenium, certain vitamins, certain types of foods, etc., could prevent prostate and other cancers. To data there is no evidence to support such findings from carefully designed clinical trials. It seems equally unlikely that just drinking coffee really does prevent prostate cancer. What is much more likely is that people who drink relatively large amounts of coffee have a series of other lifestyle behaviors which, when taken all together, really might be associated with a reduction in risk for prostate cancer (and perhaps certain other disorders). However, identifying that complete series of behaviors may be near to impossible.