The story of resistant starch continues to evolve. It is exciting to see new natural food sources of RS2 resistant starch emerge. Hopefully they will have a wider variety of taste and process tolerance than previously available.
The United States Department of Agriculture has been developing wheat hybrids with higher levels of resistant starch. These hybrids have been shown to produce pasta with acceptable quality (i.e., pasta firmness). It also ferments in the large intestine of animals (likely similar to other types of resistant starch although a comparison has not yet been done). Dr. Brittany Hazard just published a new study describing her recent work with the USDA. In addition, Arcadia Biosciences, Inc. just received a U.S. patent on October 6, 2015 (U.S. Patent No. 9,150,839) for its wheat high in resistant starch.
A group in India is now testing resistant rice starch. They have shown that their new rice hybrid developed through traditional breeding techniques has a higher amount of resistant starch than regular rice: it had a lower impact on glycemic response (incorrectly called Glycemic Index) in this 2016 clinical study.
Resistant starch from potatoes is being used by many advocates of low carb and paleo diets. It is the least expensive source and readily available. Contrary to what has been promoted within some communities, a small amount of research has been done with resistant potato starch, primarily in animals.