*Geek Box: Resistant Starch
Dietary fibre is considered the indigestible structures in edible plants, comprising both soluble and insoluble carbohydrates. Additional components to fibre include prebiotics, and resistant starches [RS], i.e., starches that are resistant to digestion and also pass to the colon, to undergo degradation by bacteria. RS is emerging as a particularly important part of overall fibre intake, and there are five types of RS.
RS1 is physically inaccessible starch that is contained within whole grains, or legumes. RS2 is a starch found in raw potatoes, underripe [green] bananas or plantains, cereals, and other starchy tubers. RS3 is also known as ‘retrograde starch’, formed when foods like potatoes or rice are cooked, and then cooled [the stickiness on the cooled starch is RS3]. RS4 is chemically modified starch to resist digestion. Recently, a fifth type has been added, based on research showing that starch:lipid complexes form when amylose starch binds with a fat.
Some interesting research is emerging to show that such complexes may reduce post-prandial glycaemia, and these complexes may have application in the food industry to make certain products, like oven chips, have less of a blood glucose impact.
Overall, the research to date suggests an enhancement of production of the SCFA butyrate, providing health benefits to the host through the multiple protective benefits of butyrate in the colon. One thing to bear in mind: most nutrition softwares and databases do not have specific data added on resistant starch yet, so it is only dietary fibre that tends to be calculated.