Resistant Starch in Rice: Its Biosynthesis and Mechanism of Action Against Diabetes-Related Diseases

Rice with a high resistant starch (RS) content is one the most commonly used, effective, and safe functional foods, which can be used to prevent diabetes and its related complications in humans. Based on the health benefits (highest to lowest), the types of RS can be categorized as follows: RS1> RS3> RS5> RS4> RS2. Here, we discuss the biosynthesis and mechanism of action [processing changes, biochemistry, and glycemic index (GI)] of the five RS types present in rice as well as their potential of preventing diabetes-related diseases, based on reports published from 2004 to 2021 in PubMed, CNKI, and ISI Web of Science databases. High-RS rice has gained considerable interest owing to the advantages it offers as a staple food product and its potential for controlling appetite with satiety, lowering glucose levels in the stomach and small intestine, and increasing the short-chain fatty acid content in the large intestine, which helps combat metabolic syndrome by controlling gluconeogenesis, promoting glycogenesis, maintaining glucose and lipid homeostasis, and improving pancreatic function. Rice is an important source of RS (>3%, GI<55) and can help prevent diabetes. However, certain types of rice have a high GI (>85), which may induce metabolic syndrome. The RS content of rice ranges from 0.1% to 25.4% and the GI ranges from 44 to 132, which has many factors relating in the white rice. In this review, we discuss the diversity in RS content based on the biosynthetic mechanism and the mechanism of action of high-RS rice in diabetes. We also discuss potential limitations of rice breeding programs and the methods that can be used to ensure the availability of effective, yet palatable, high-RS rice.