The Different Fractions of Resistant Starch

Resistant starch (RS) can be classified into four different fractions based on their physical and chemical properties: RS1, RS2, RS3, and RS4.

1. RS1: This is the physically inaccessible fraction of resistant starch, such as starch trapped in intact plant cells or bound to fibrous cell walls. It is present in whole grains, seeds, and legumes. RS1 is resistant to enzymatic digestion in the small intestine and can therefore reach the large intestine where it can be fermented by gut microbiota. Potential health benefits of RS1 include the promotion of healthy gut microbiota and the reduction of the risk of colon cancer.
2. RS2: This is the resistant starch granule fraction, such as uncooked potato, green banana, and high-amylose maize starch. It is resistant to digestion due to its crystalline structure, and like RS1, it can reach the large intestine where it can be fermented by gut microbiota. RS2 has been shown to improve glycemic control, reduce insulin resistance, and increase satiety.
3. RS3: This is the retrograded starch fraction, such as cooled cooked potato, rice, and pasta. Retrogradation occurs when cooked starch is cooled, causing the starch molecules to re-form into a crystalline structure. RS3 is resistant to digestion in the small intestine and can therefore reach the large intestine where it can be fermented by gut microbiota. Potential health benefits of RS3 include the promotion of healthy gut microbiota, the reduction of postprandial glycemic response, and the reduction of the risk of colon cancer.
4. RS4: This is the chemically modified fraction of resistant starch, such as esterified and cross-linked starches. It is resistant to digestion due to chemical modifications and can reach the large intestine where it can be fermented by gut microbiota. The potential health benefits of RS4 are similar to those of other RS fractions.

Overall, the potential health benefits of resistant starch consumption include the promotion of healthy gut microbiota, improved glycemic control, increased satiety, reduced energy intake, and the reduction of the risk of colon cancer. However, more research is needed to fully understand the health benefits and optimal intake levels of resistant starch.