It is nice to report good news. In this case, the good news is that a recent study of prostate cancer found that drinking coffee reduced risk.

It is always essential to view dietary studies skeptically. There are so many reasons they can be misunderstood, or just plain wrong. The world is too complicated to neatly study it. It is very difficult and ethically dubious to conduct ideally controlled dietary research. A little story about such presumptions might help.

One day a student in the homeopathy class I used to teach in the UCSF medical school inadvertently dramatized the assumptions one can make about research overlooking the requirements of studies in the real world. Seeking to discredit my research credentials, he belligerently demanded to know where my lab was. I pointed out that, despite the advantages to science, people just do not like being locked up in cages for the convenience of scientists.

Wild humans, living in their natural environment, have an annoying habit of eating a variety of mixed up food items with such unpredictability that their eating patterns seem almost whimsical. It is as if they actually select what they eat based upon some internal preference or external appearance. They/we are then extremely poor experimental subjects. I hope he went into basic sciences research or had some humanistically transformative experience. He did apologize, so there is hope for his wizened soul.

Although still far from certain, the most reliable research data comes from intervention studies. One group of people, exactly the same as another group, is treated differently and watched to see what happens. Yes, this is potentially every bit as creepy as the medical student’s thoughtless question. Studies of the long-term effects of dietary differences are essentially impossible. Would you volunteer for a study where someone else would tell you what you could and could not eat for a decade or two?

Despite the inevitable weaknesses, this study is relatively compelling. That is because the effect was proportional to the amount of coffee consumed. In other words, a bit of coffee reduced the risk, while a lot of coffee reduced risk a lot. Six cups a day (not unusual in Scandinavia where the study took place) reduced the risk of developing of prostate cancer by 20% and the death rate from prostate cancer by 60%. Coffee would seem then to prevent the worst forms of prostate cancer.

As the risk reduction persisted when the coffee was decaf, the most likely anti-cancer effect is the antioxidants in the coffee. Now, if that theory holds water (sorry), a cup or two of Mediterranean coffee, which typically has 50x higher levels of antioxidants then the coffee most of us drink, should have really powerful effects. It would also be a more tolerable means to achieve the results. Six cups of coffee a day would have me bouncing off the ceiling, not just the walls. Other studies, including studies of high blood pressure and Alzheimer’s, suggest that coffee has benefits beyond the buzz and flavor desired by so many. The blood pressure study specifically considered Mediterranean-style coffee (finely ground coffee heated in water short of boiling temperatures), which is very different from the coffee most of us drink. Due to the uncertainties of such research, the complexity of compounds in “coffee” and the fact that many people react badly to some types of coffee, further study is warranted. Unlike most medical research, I am sure that recruiting subjects will not be a problem!


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Michael Carlston, MD is an internationally recognized authority in the integration of conventional and complementary medicine in clinical practice, as well as medical education, research and organizational consulting. Practicing in Santa Rosa, California, Dr. Carlston was voted “Best General Physician In Sonoma County, California” by readers of the Sonoma County Independent newspaper and also named one of the outstanding physicians in the Bay Area by San Francisco Focus Magazine. With 30+ years in private practice, his expertise is in nutrition, homeopathy and sports medicine.

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