7 signs your body could be sensitive to coffee

You Really, Really Have To Pee

Caffeine can also affect sensitive people's GI tract, causing some rather unpleasant side effects. "People who are caffeine sensitive may notice stomach upset when they drink caffeine while others may notice diarrhea," Hutlin says. "Studies are mixed on why this happens — whether it may be a shift in hormones when caffeine is consumed, or other compounds in coffee could stimulate the bowels."