Starch digestion: A comprehensive update on the underlying modulation mechanisms and its in vitro assessment methodologies

Background: Starch is the predominant carbohydrate in our diets and its impact on human health is intricately linked with its digestive process. However, despite major advancements in the field, important inconsistencies in how starch digestion is described and studied in vitro still persist. Scope and approach: Our main objective was to provide up-to-date insights on starch digestion and fermentation in the human gastrointestinal tract, as well as related physiological responses and main drivers of variability (including inter-individual variations and structural and compositional differences between foods). A critical appraisal of digestion models and future work priorities is also presented. This work is the product of an international collaboration within the INFOGEST research network. Key findings and conclusions: Starch digestion is accomplished by the concerted action of luminal and brush-border hydrolases. Mechanical and biochemical transformations occurring throughout oral, gastric and intestinal phases can be determinant, contributing to different extents to the digestive process depending on food properties and individual characteristics. Numerous methodologies, with varying complexity and capacity to reproduce key digestive processes (e.g., gastric emptying), are currently available. Some in vitro digestibility outcome measures can be closely correlated with the outcomes of in vivo studies, demonstrating the promising potential of these approaches. However, the physiological relevance of in vitro starch digestion studies is often compromised by the lack of methodological consensus (particularly for oral digestion) and omission of key enzymatic events. Therefore, the need to develop harmonized guidelines and validate in vitro protocols adapted to starch digestion studies stand out as priority areas for future work.