Fungal protease is an enzyme derived from fungi, commonly Aspergillus species, and is used in dietary supplements to aid protein digestion. Its primary role in supporting the small intestines relates to its ability to break down dietary proteins into smaller peptides and amino acids, facilitating their absorption in the small intestine. There is scientific evidence indicating that supplemental proteases, including those from fungal sources, can increase protein digestibility, especially in individuals with suboptimal digestive enzyme production (e.g., pancreatic insufficiency, aging adults). Several in vitro and human studies have shown that fungal proteases remain active at the pH range found in the stomach and small intestine, supporting their functionality in the digestive tract.

However, the direct evidence that fungal protease supplementation specifically improves small intestine health or function in otherwise healthy individuals is limited. Most research focuses on general protein digestion and nutrient absorption rather than clinical outcomes related to small intestinal health. Fungal proteases are widely used in the food industry and in enzyme therapy for digestive support, and they are considered safe for most people. While there is a plausible scientific basis for their use and some supporting data, the strength of evidence is moderate and not conclusive for targeted small intestine health beyond their general digestive support role.