Although you can take resistant starch as a supplement powder, you can find resistant starch naturally in oats, cooked then cooled rice, and beans. Green bananas and plantains are higher in resistant starch, but the starch turns to sugar as the banana ripens.
A 2022 article in Cancer Prevention Research looked at how resistant starch and aspirin might affect the risk of cancer in people with Lynch syndrome. People were given 30 grams of resistant starch to take every day for four years, then the researchers followed up about 20 years later. Even though the resistant starch didn’t decrease the risk of colorectal cancer, it did reduce the risk of other cancers that are often linked with Lynch syndrome.
The bacteria in your gut break down resistant starch and produce butyrate, which can protect against cancer, especially the types of cancer linked to inherited mutations. The researchers also believed that resistant starch might reduce cancer by lowering harmful secondary bile acids.