What happens to your body when you suddenly stop drinking coffee? To find out, researchers from University College Cork in Ireland studied 62 people, half of whom regularly drank three to five cups of coffee a day and the other half who didn't usually drink coffee. They examined gut bacteria, metabolites, mood, stress, alertness, learning and memory. Regular coffee drinkers first stopped drinking coffee for two weeks, during which time the researchers measured changes in their bodies and behavior.