There are various ways that starch can be resistant to digestion, which has led to the categorization of RS into five types (RS1–RS5), with RS2 being the most studied supplemental form.[1][2]
- RS1: Starch that is protected within plant cell walls, such as in seeds, grains, or legumes.
- RS2: Starch granules that are indigestible due to their dense crystalline structure, like those found in green bananas and raw potatoes.
- RS3: Retrograded starch, which is formed when certain starchy foods — like potatoes, oatmeal, and rice — are cooked and then cooled.
- RS4: Starch that has been chemically modified and may be found as a food additive in some commercially made breads or pastries.
- RS5: Starch that has been complexed with fats, which can be made artificially or occur naturally when starches are cooked in the presence of fats.
Current research suggests that the different types of RS likely produce unique effects, but more research is needed to understand these differences.[3][4]