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2013-08-30

Coffee: Friend or Foe?

Here are two interesting and almost contradictory studies on coffee. In the first study, researchers report that heavy coffee consumption of more than 28 cups weekly (an average of 4 cups daily) was associated with an increased risk of "all-cause" mortality among men. This association was more pronounced for those under 55 years of age.

Previous studies had suggested an association between heavy coffee consumption and all-cause mortality and coronary heart disease, but many of these older studies are compromised, because heavy coffee drinkers were also smokers, two habits that went hand in hand in the yesteryears. When adjusted for smoking, coffee didn't appear to be too harmful, and in fact, most of the more recent studies suggested that coffee consumption offers a number of potential benefits as I discussed in a number of posts in the last few years:




In the multivariate analysis, men who drank more than 28 cups of coffee had a statistically significant 21% increased risk of all-cause mortality (but in women, the risk was not statistically significant). In men younger than 55 years of age, drinking more than 28 cups per week was associated with a 56% increased risk of death compared with nondrinkers. In younger women, such heavy consumption increased the risk of death 113% compared with those who did not drink coffee.

Overall, there was no association between coffee consumption and cardiovascular mortality, and noncardiovascular mortality includes a lot of different things (cancer, suicides, accidents, infections, etc.). It's not clear why only noncardiovascular mortality increased, but it's likely a correlation, not a cause-effect relationship.

Despite the limitations of the study, up to about 28 cups a week doesn't seem harmful at all. However, the lead author makes a point to note that a cup of coffee as measured is an 8-oz cup, and not the super-sized 20-ounce cups typical of Starbucks (the Venti size) and other coffee chains. This contradicts a number of other studies that previously suggested that the health benefits of coffee kick in after about 4-5 cups daily, like the next study below. Of course, with everything, it's the dose that makes the poison, so finding a balanced consumption is best, but in this case the "toxic" dose and "health-promoting" dose seems to be the same! Hmmm...
 Source: Association of coffee consumption with all-cause and cardiovascular disease mortality

The next study of discussion involved 1001 prostate cancer survivors (of which 630 met the criteria for inclusion in the statistical analysis), aged 35-74 years old at the time of diagnosis. This study found that, at 4 or more cups of coffee daily, bioactive compounds in coffee and tea had preventative effects on prostate cancer recurrence or reduced progression of the disease. The research team found men who drank four or more cups of coffee daily had a 59% reduced risk of prostate cancer recurrence and/or progression (compared to those who drank only one cup or less per week). This is not the first time coffee consumption has been linked to prostate cancer risk, as I discussed a couple years ago.

Source: Coffee and tea consumption in relation to prostate cancer prognosis

Where does that leave us? Well, most of the better designed studies of recent years suggests health benefits, but we can't ignore the negative studies. Until we can understand things more, I don't see any reason for anyone to change their current consumption rates.

Enjoy your long weekend, and the last weekend of the summer! (...yes, I still talk like a student, as if I've had the last couple months off.)  :)

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