Great question! Coffee is a natural diuretic (makes you have to pee), and for many people it also has a laxative effect (makes you have to poop). This is partly because the main active component in coffee is caffeine, and also because of other aspects such as the high acidity of coffee. Caffeine stimulates your digestive system and prompts bowel movements. If your coffee is hot, it will further relax your system due to the temperature, increasing the laxative effect. Common side effects from drinking coffee include stomach upset, diarrhea, increased heart and breathing rate, jitters and restlessness, and difficulty sleeping, among others.
The American Academy of Pediatrics recommends that children and adolescents do not drink any caffeine, because we don’t know how it affects growing brains and bodies. Instead, they suggest sticking to water, milk, and juice in limited amounts. Reducing your coffee intake will help to alleviate unwanted symptoms, including the unpleasant digestive side effects. Slowly decreasing your coffee intake can help to avoid any unwanted caffeine withdrawal symptoms (like a headache).