On the one hand, bananas are rich source of dietary fiber, which can reduce constipation. On the other hand, bananas have high starch content, especially in unripe bananas and banana is sticky so it can cause the bowel to stick to rectum wall. In this sense, bananas can cause constipation, especially if you are constipation prone.

It is important to know that consuming ripe bananas in moderate, while combining with other fruits high in fiber will improve bowel movements and is not likely to cause constipation.