Having GI distress after a cup of coffee is more than enough reason for some folks to swear off the stuff. Like so many things around food and how our bodies process it, the subject of what causes such distress is often up for debate. Edwin Martinez of Hario USA & Finca Vista Hermosa posited that the negative reactions to coffee could be based in rancid oils or over-roasted beans. Some folks think that maybe it's just sheer acidity in the bean itself.
But a new group of scientists who are studying the nutritional benefits of processed foods versus totally raw foods have found that a stomach-friendly compound called N-methylpyridinium (NMP) that appears in coffee beans only after the roasting process actually decreases the amount of acid that stomach cells produce in response to coffee. To test out stomach cell reaction to coffee, they used a combination of water and solvents to extract compounds from some different coffee blends, then exposed them to the cells. Except for NPM, the cells increased their acid production in response to the compounds.
So maybe darker roasts aren't going to give you the same rainbow of flavors that a medium roast coffee might, but it may be easier on the ol' tum tum -- and if that's a concern for you, choosing a darker roasted bean may be the key to you enjoying a cup of morning java.