Apples are known to cause digestive issues including bloating, cramps, gas, and diarrhea due to their sorbitol content. Sorbitol is a sugar alcohol that cannot be broken down properly in the stomach or small intestine, and instead lands undigested in the large intestines.
The large intestine is tasked with pulling water out of waste products, but too much sorbitol can cause the intestinal wall to release all that water back into the colon. The result is digestive pain including diarrhea, in fact, sorbitol is an active ingredient in many laxatives.
Sweeter red apples may be the tastiest, but tarter green apples contain a lot less sorbitol and are better for people who experience digestive distress. Apples should be avoided entirely by people with irritable bowel syndrome.