Roughly two-thirds of Americans drink coffee daily, according to a July 2015 Gallup poll. Coffee can stimulate the movement of stool through the intestines by promoting muscular contractions of the bowels. This short-term stimulation is not significant enough to cause diarrhea in most people. However, individuals respond differently to various foods and beverages, and some people might be exceptionally sensitive to the intestinal effects of coffee. Therefore, it's possible that coffee might cause diarrhea, but this effect is generally unlikely.
Caffeine and Beyond
The caffeine in coffee is a nervous system stimulant. One effect of this stimulation is a short-term increase in muscular contractions in the bowel, although not all people experience this effect. Among those who do, drinking coffee can lead to the urge to have a bowel movement shortly afterward. While the bowel stimulating effect of coffee has usually been attributed to its caffeine content, a similar effect has been seen with decaffeinated coffee in at least one study -- although the research on this topic is limited. Nonetheless, it appears that the laxative effect of coffee is mild and is not sufficient to cause diarrhea in most people.
Everyone is Different
While coffee is unlikely to cause diarrhea, that does not mean it's not a problem for you. At least one small study published in the journal "Digestion" in 2001 found that coffee was among the most common foods reported to cause symptoms -- including diarrhea -- in people with irritable bowel syndrome (IBS). If you experience frequent diarrhea, keeping a food diary can help you identify what foods and beverages seem to correlate to your symptoms.
Diarrhea is a common symptom caused by a wide variety of medical conditions, some of which can be serious. See your doctor if you experience frequent diarrhea to determine the cause and appropriate treatment. Seek medical care as soon as possible if you have accompanying symptoms that might indicate a serious problem, including:
-- unintentional weight loss
-- bloody or tarry stools
-- persistent, severe or worsening abdominal pain
-- fever or chills
Reviewed by: Tina M. St. John, M.D.