Starch digestion in the upper gastrointestinal tract of humans

Starch provides a large proportion of the dietary energy consumed worldwide. The breakdown of dietary starch is driven by α-amylase produced by the salivary glands and pancreatic acini and is completed by a range of brush-border bound enzymes. This enzymatic digestion is aided by mechanical and secretory actions of the gastrointestinal tract. The absorption of the resultant glucose in the small intestine is primarily driven by two separate transport proteins − SGLT1 and GLUT2. The control of processes that govern starch digestion is complex and still not fully understood, although it appears that the human gut has the ability to sense both glucose and non-sweet glucose oligomers. Recent work has also suggested that variations in the genes encoding for α-amylase also appear to be associated with health outcomes. The authors consider the physiological factors that govern starch digestion and absorption, consider other dietary factors that may impact on this process and attempt to highlight the limitations in current knowledge to help focus future research needs in relation to starch digestion the upper gastrointestinal tract.