What makes a starch “resistant”?

Resistant starch is a type of starch that isn’t fully broken down and absorbed, but rather turned into short-chain fatty acids by intestinal bacteria.

This may lead to some unique health benefits. To get the most from resistant starch, choose whole, unprocessed sources of carbohydrate such as whole grains, fruits, vegetables, and beans/legumes.

All starches are composed of two types of polysaccharides: amylose and amylopectin. (For more on polysaccharides, see All About Carbohydrates.)

Amylopectin is highly branched, leaving more surface area available for digestion. It’s broken down quickly, which means it produces a larger rise in blood sugar (glucose) and subsequently, a large rise in insulin.

Amylose is a straight chain, which limits the amount of surface area exposed for digestion. This predominates in RS. Foods high in amylose are digested more slowly. They’re less likely to spike blood glucose or insulin.

Thus, resistant starch is so named because it resists digestion.

While most starches are broken down by enzymes in our small intestine into sugar, which is then absorbed into the blood, we can’t fully absorb all kinds of starch.

Some starch — known as resistant starch (RS) — isn’t fully absorbed in the small intestine. Instead, RS makes its way to the large intestine (colon), where intestinal bacteria ferment it.

Resistant Starch is similar to fiber, although nutrition labels rarely take RS into account.

Cassava starch