RODALE NEWS, EMMAUS, PA—Coffee perks you up, lowers your risk of heart disease, and has antioxidants that ward off cancer. It's even a mild painkiller: Drinking a few cups before you exercise can prevent post-workout muscle aches and pains. So you could be missing out if you fall into the crowd of 40 million people who don't drink coffee because of stomach irritation. The good news, according to a new study presented at a recent meeting of the American Chemical Society, if coffee upsets your stomach, you could just be drinking the wrong kind. The researchers found that dark-roasted coffees are easier on the stomach than light or mild roasts because they contain a particular ingredient that keeps your stomach from producing too much acid.

THE DETAILS: A number of companies have come out with "low-acid" coffees catering to people with sensitive stomachs, but no studies have ever been done to show whether these low-acid drinks are free of the compounds in coffee that cause stomach irritation or, for that matter, what the exact compounds are that irritate stomachs. For this study, the researchers took human cells that regulate acid secretion in the stomach and exposed them to different types of coffee: regular, dark-roast, mild, decaffeinated, and low-acid. They found that different compounds in the different roasts had compounds that do indeed cause stomach cells to produce more acid. The main culprits were caffeine and two different plant compounds, catechols and N-alkanoly-5-hydroxytryptamides. But they also found that another compound, N-methylpyridinium (NMP), had the opposite effect. NMP was generated as the coffee beans were roasted, and the longer they roasted, the higher the levels of NMP that were present.

WHAT IT MEANS: These findings should be good news for anyone who's been avoiding coffee because of stomach upset. The researchers found that dark-roasted coffee can contain as much as twice the levels of the stomach-friendly compound NMP as light-roasted coffees, though that can vary depending on the variety of the bean. Their research also found that coffees being marketed as low-acid or easy on the stomach should work. Manufacturers of those coffees usually treat raw coffee beans with steam or other chemical solvents, such as ethyl acetate and dichloromethane, prior to roasting, and the study's authors found that those methods do in fact lower the levels of acid-producing compounds.