Malt diastase is an enzyme derived from malted barley or other grains, primarily containing alpha-amylase activity. Its main function is to catalyze the breakdown of starches into simpler sugars, such as maltose and glucose. The rationale for its use in supporting the small intestines is based on its digestive aid properties: by assisting in the pre-digestion of dietary starches, malt diastase can potentially reduce the burden on endogenous intestinal enzymes, facilitating more efficient carbohydrate absorption in the small intestine.

Scientifically, there is moderate evidence supporting the use of supplemental digestive enzymes, including malt diastase, for individuals with impaired starch digestion (e.g., pancreatic insufficiency, certain malabsorption syndromes). Clinical studies have shown that exogenous amylase enzymes can improve carbohydrate digestion and reduce gastrointestinal symptoms such as bloating and discomfort in affected populations. However, for healthy individuals with normal digestive function, the benefit is less clear, as the body typically produces sufficient endogenous enzymes.

While tradition has long included malt extracts in digestive tonics, modern support for malt diastase's role comes from enzyme supplementation studies and its use in managing specific digestive disorders. Overall, the use of malt diastase to support small intestine function is scientifically plausible, particularly in cases of enzyme deficiency, but evidence is not robust across all populations.