From Arnold's Pump Club newsletter. A 22,000-Person Study Tested 150 Foods for Gut Health. Coffee Was A Big Winner. Scientists tested 150 foods for their impact on gut bacteria, and coffee ranked first by a wide margin, boosting levels of a bacterium called Lawsonibacter asaccharolyticus by 4.5 to 8 times compared to non-drinkers. Decaf produced nearly identical results, which point researchers toward coffee's polyphenols — specifically, chlorogenic acid — rather than caffeine as the likely driver. That bacterium helps your body produce butyrate, a compound your gut lining depends on to stay intact and keep inflammation in check, which may help explain coffee's long track record of health benefits.