Ripe bananas are relatively high in fiber with one medium banana containing 3 g fiber, mostly in the form of soluble fiber to met about 10 percent of daily fiber needs.

Soluble fiber soaks up water and turns to gel during digestion, which helps bulk up your stool and guard against constipation and diarrhea; soluble fiber attaches to cholesterol particles and takes them out of the body, helping to reduce overall cholesterol levels and the risk of heart disease.

(Sources of Information: ncbi.nlm.nih.gov, medlineplus.gov & webmd.com)