Can caffeine in drinks such as Mountain Dew and Dr. Pepper cause diarrhea?

C.S.

It is not common to suffer from diarrhea, which is characterized by very loose, watery stools, after drinking caffeinated soft drinks or even after drinking coffee. However, some people do get a strong urge to have a bowel movement after consuming caffeine.

If what you are experiencing is the need to have a bowel movement (which may or may not be less formed than a usual stool) after drinking highly caffeinated drinks (such as Mountain Dew), the following mechanisms are likely at play. A common reflex, called the gastrocolic reflex, stimulates the colon to contract after a meal. It is not clear why the body has this reflex, and it is more pronounced in some people. Although drinking a soft drink is not equivalent to a large meal, the carbonation in the drink can distend the stomach and lead to this reflex. In addition, caffeine can also stimulate the intestine, resulting in forceful colonic contractions and a bowel movement after consuming food or beverages with a high caffeine content.

If you are having true diarrhea, it is likely due to some other problem and you should see a doctor who can order the necessary tests to make the diagnosis.