Photo by nate steiner/FlickrCC
I tried to follow a few of the articles back to the full paper, but was unsuccessful. Sometimes the abstract was available free online, but not the full paper--at least in the two I pursued. I am always looking for a definition of "a cup" or "a serving" and the brew strength. As we've discussed, coffee strength varies considerably, and caffeine content varies enormously among coffees.
I'd like researchers to be specific about strength (grams per liter) and caffeine content (if that's presumed to be the important constituent for the study) and serving size.
Another source for peer-reviewed articles on coffee and health is Cosic.org which is funded by a small number of European coffee roasters.
It's mostly happy news. Read carefully, but most of us can enjoy another cup.
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At least for the Circulation article they mention, the researchers used data from the USDA (in 1984) to come up with the following for caffeine levels (per "cup"): coffee, 137mg; tea, 47mg; "can or 12oz bottle of soda", 46mg; 1oz chocolate candy, 7mg. They added each up and divided by a weight of caffeine per frequency of each food eaten by each patient, according to diet questionnaire and some weekly diet journals.
Not really sure how we decide that an 8oz can and a 12oz bottle of soda have the same caffeine level, but I would suspect that most medical researchers will just use the USDA numbers, since they're available and "official." The researchers in this article do mention that their caffeine data is "supplemented by other sources," but they do not name any.
-- K Sargent, MD
Jerry, Cosic.org isn't the only source for coffee research which is funded by members of the coffee industry, nor the only one with "mostly happy news" about coffee and caffeine. Vanderbilt University's Institute of Coffee Studies is funded by the Brazilian Coffee Assn, alaong with other coffee growers, starting with $6 million, which pays for ("sponsors")research on coffee's health benefits.
Sponsored studies invariably produce results favorable to the economic interests of the sponsor. Coffee growers want to sell more coffee!
Ethic Soup has some excellent articles on coffee and caffeine, including health risks at:
http://www.ethicsoup.com/caffeine-the-worlds-most-popular-drug.html