Arabinoxylan is a type of hemicellulose, a non-starch polysaccharide found in the cell walls of cereal grains such as wheat, rye, and barley. Its primary relevance to the small intestine stems from its function as a dietary fiber and prebiotic. Scientific studies have shown that arabinoxylan is resistant to digestion in the upper gastrointestinal tract, including the small intestine, and reaches the colon relatively intact where it is fermented by the gut microbiota. However, some fermentation and interaction with gut microbes can begin in the distal small intestine.

Evidence suggests that arabinoxylan can modulate the gut microbiota, enhance the growth of beneficial bacteria (such as Bifidobacteria and Lactobacilli), and promote the production of short-chain fatty acids (SCFAs), which are important for intestinal health. While most of these effects are pronounced in the colon, some prebiotic effects may influence the environment of the distal small intestine as well. There is also evidence that arabinoxylan may help regulate intestinal transit time and improve gut barrier function, which could indirectly support small intestine health.

However, the majority of the scientific evidence focuses on arabinoxylan's role in overall gut health and colonic fermentation rather than direct, targeted effects on the small intestine specifically. Therefore, while there is moderate scientific support for its use in supporting gut and intestinal health, the evidence for benefits exclusive to the small intestine is limited.