Green banana (unripe banana) is a functional food that has been studied for its effects on the small intestine, primarily due to its high content of resistant starch and dietary fiber. Resistant starch is a type of carbohydrate that resists digestion in the small intestine and reaches the colon, where it is fermented by gut microbiota. This fermentation process produces short-chain fatty acids (SCFAs), such as butyrate, which play important roles in maintaining intestinal health, supporting the intestinal barrier, and modulating inflammation.

Clinical and preclinical studies have shown that green banana flour or green banana-based dietary interventions can help manage diarrhea, especially in children. For example, randomized controlled trials in children with persistent diarrhea demonstrated that green banana supplementation reduced the duration and severity of diarrhea, likely by improving mucosal healing and supporting water and electrolyte absorption in the small intestine. These effects are attributed to the resistant starch content, which enhances the growth of beneficial gut bacteria and the production of SCFAs.

However, while there is scientific evidence supporting the use of green banana for intestinal health, particularly in the context of diarrhea management and gut microbiota support, evidence specifically targeting other small intestine functions is more limited. Overall, the use of green banana is justified by moderate scientific data, especially in pediatric gastrointestinal health and as a prebiotic food.