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One study 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.
For the study, 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.
Related: 9 Incredible Health Benefits Of Coffee
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 because they lower levels of acid-producing compounds, but you may not want to drink them for other reasons. Manufacturers of those coffees usually treat raw coffee beans with steam or other chemical solvents, such as ethyl acetate and dichloromethane, prior to roasting. (Check out what happened when one writer swapped her morning coffee for matcha tea.)
So, if you want to enjoy coffee but don't want to expose yourself to chemical solvents, the easiest thing to do is try dark-roasted coffees first. But which one should you buy? Here are a few tips on reading labels.
Look for geographic names
Some coffee companies are explicit and label coffees as "medium roast" or "dark roast." Others, however, use coffee terminology to describe their roasts, and more often than not the names are geographic.
Medium-dark roasts include Viennese, Full City, Light French, Continental, After-Dinner, and European. The next level up includes French (like this organic, Fair Trade option from Equal Exchange), Espresso, Italian, and Turkish roasts, followed by Neopolitan or Spanish roasts. Those last two have been roasted so long at such high temperatures that they usually taste burned or charred.
Another upside to drinking darker roasts is that they have less caffeine, which can trigger stomach irritation. But if caffeine continues to irritate your stomach, opt for dark-roasted decaf. (Here are some surprising things that happen when you quit caffeine.)
(Not into coffee? Consider trying a kombucha tea slushie for a super subtle caffeine boost.)
Pay attention to color
Coffee beans start out green and then turn brown as they're roasted, gradually growing darker until they're nearly black for the darkest roasts. If you're shopping somewhere that allows you to see the beans before you buy them, you can usually tell by looking at the color whether it's a dark or a medium roast. (Watch out for these 8 ways you're ruining the health perks of your coffee.)
Remember the trifecta
While you're shopping for stomach-friendly coffee, remember to buy certified-organic coffee (grown without pesticides), Fair Trade Certified coffee (grown by farmers in developing countries who were paid above-market rates for their crops), and shade-grown or Bird Friendly coffees (which were grown under shade canopies that serve as habitats for native birds). Not only are these better for the planet, but they've also been shown to have higher levels of antioxidants.