Unlike typical carbohydrates which are digested and turned into glucose within a certain time frame depending on the type of carbohydrate that it is, resistant starch doesn’t behave that way. Instead it acts like an indigestible fiber and “resists digestion”. Resistant starches are made of amylose and don’t get digested in the stomach or small intestine and reach the large intestine (colon) intact. And since they are digested more slowly, they are less likely to spike glucose or insulin. Once in the colon, resistant starch is turned into energy boosting, inflammation fighting short chain fatty acids such as butyrate by intestinal bacteria. Butyrate is a preferred energy source for colonic cells and increases our metabolism and decreases colon permeability so that toxins don’t enter your bloodstream. Increasing other short chain fatty acids (SCFAs) such as acetate, and propionate in addition to butyrate, also stimulate blood flow to the colon, increase nutrient circulation, inhibit the growth of pathogenic bacteria, promote the growth of good bacteria, and help us absorb minerals.
Examples of resistant starches
Corn, beans and legumes, tubers, white and sweet potatoes, carrots, un-ripened bananas and plantains, winter squashes, rice, and grains. Technically it could be divided into four groups.
Type 1: starch bound by indigestible plant cell walls, found in beans, grains and seeds
Type 2: starch that is indigestible in the raw state due to high amylose content. Potatoes, bananas and plantains, but the starch becomes accessible upon heating.
Type 3: Retrograded starch. A starch that has been heated and cooled which makes it more resistant to digestion, found in cooked potatoes, grains, and beans.
Type 4: Industrial resistant starch. Potato starch or hi-maize resistant starch. Not natural and has been chemically modified.
Resistant starch and weight loss
Because resistant starches are incompletely digested, we only extract about 2 calories of energy per gram versus about 4 calories per gram from other starches. Therefore, 100 grams of resistant starch is only 200 calories while 100 grams of another starch gives us 400 calories. Foods high in resistant starch fill you up, without filling you out. Resistant starches appear to lower glucose levels and improve insulin sensitivity which leads to a decreased appetite. When resistant starches increase SCFAs they in turn increase leptin and pancreatic peptide YY (two hormones) both of which suppress our appetite.
Cooking and resistant starches
Rice is the most common exposure of resistant starch in the world. One cup of cooked rice contains around 240 starchy calories that can be quickly turned into fat if they are not burned off. However, Suhair James, an undergraduate chemistry student form the College of Chemical Sciences in Sri Lanka discovered a new way of cooking rice that cut its calories by as much as 50% and decreased the amount of digestible starch by 15 times! His work was presented to the National Meeting and Exposition of the American Chemical Society. His solution was quite simple. He added about a teaspoon of coconut oil to boiling water before adding a cup of rice. The oil works by interacting with the starch molecules and changes its architecture. Cooling (refrigeration) for 12 hours will lead to the oil forming hydrogen bonds between the amylose molecules outside the rice grains which turns it into a resistant starch! Therefore, three major observable benefits occurred from Mr. James’ study.
- How the addition of oil while cooking changed the amount of resistant starch.
- The effect of cooling on increasing resistant starch content.
- How the above two processes cut the calorie content of rice by 50%.
Other benefits of resistant starches
It brings down cholesterol and triglyceride levels. It adds bulk and water to your stool. In developed countries like ours, we consume about 3-9 grams of resistant starch per day. In developing countries, the intake of resistant starches tends to be about 30-40 grams per day. However, a word of caution. If you are unaccustomed to resistant starch it is best to gradually increase the amount of resistant starch in your diet otherwise gas, bloating, and cramps will occur. If symptoms like this do happen, it is likely that the person is low in SCFAs. There is also a supposed benefit with sports performance and resistant starches. It is believed that during long endurance events, utilizing a low glycemic carb source like resistant starch can limit insulin spikes and maximize fat burning as a source of energy during the event. One company UCAN makes such a starch from non-GMO corn. Although it is an industrial resistant starch there is evidence of its ability to maintain blood glucose levels during seven hours of prolonged exercise to no more than a 4% drop in blood sugar. In comparison to manufactured sports drinks and gels which are high in sugar, UCAN is light years ahead of them functionally and their “Super Starch” prevents the glycemic roller coaster effect that those other products contribute to. Those sugar/insulin spikes lessen our ability to access the stored fat we have that we use for energy during prolonged activities.
Resistant starches are like a superfood for the digestive system and beyond. It can provide the substrate for the body to make essential short chain fatty acids that help our immune system, and overall health. They give us a feeling of satiety by balancing hormones associated with hunger and cravings such as insulin, glycogen, leptin, and ghrelin.