Starches are large chains of carbohydrates found in the granules of plants. Starches can either be found in straight chains (amylose) or branched chains (amylopectin) and both are a source of dietary carbohydrate and energy. The structure of a starch influences how well it is digested and because of this, not all starches are equally well digested by the enzymes in our digestive system. Starch that passes through the small intestine undigested is a type of dietary fiber that is known as resistant starch.[fn value=1][/fn]

Resistant starches haven been shown to confer health benefits when consumed in the diet. They have been studied for the past 30 years in both animals and humans and support the health of the large intestine as well as systemic organs.[fn value=2][/fn] [fn value=3][/fn]

When resistant starches reach the colon, the microbiota can convert these starches into short chain fatty acids (SCFAs) that:

• Support immune development
• Provide energy for colonic cells
• Promote feelings of fullness
• Create a more acidic environment in the colon, which has been shown to increase the uptake of minerals, such as calcium, as well as inhibit the absorption of toxic compounds and inhibit the growth of certain unwanted bacteria

There has been a significant amount of research performed regarding resistant starch and its health effects recently. Studies show that resistant starch consumption results in a more acidic colonic environment, which is known to inhibit growth of harmful bacteria. Compared to other types of fiber, resistant starch has been shown to be more effective in promoting healthful colonic environment, suggesting resistant starches may be an optimal fuel source for the gut microbiota.[fn value=4][/fn] Other studies show that dietary modifications including adding more resistant starch to the diet influence the makeup of the gut microbiota in such a way that it can modulate inflammation in the colon.[fn value=5][/fn]

Only recently has data highlighted the fact that increasing the resistant starch content of rice, potatoes, and pasta can actually reduce the total caloric content of the food. Studies indicate that creating resistant starch in foods can reduce their caloric content by ~20%, but in some cases as much as 60%![fn value=6][/fn]

Furthermore, fermentation of resistant starch has been shown to promote satiety though alterations in the production of neurochemicals that are responsible for giving us a feeling of “fullness”.[fn value=7][/fn]

Intake of resistant starch has also been found to support healthy blood sugar levels. Subjects consuming resistant starch with their meal had lower levels of post-meal blood glucose and insulin. In adults with untreated borderline diabetes, consuming as little as 6 grams of resistant starch in a meal had beneficial effects on blood glucose levels.[fn value=8][/fn]

Resistant starch intake is difficult to estimate in the standard American diet, although it is estimated to be around 5 grams per day. It has been reported that Europeans and other Western countries consume between 3 to 9 grams of resistant starch per day, whereas intakes in other countries that follow more traditional diets have been estimated to be between 10-20 grams per day.[fn value=1][/fn][fn value=2][/fn]

Cooked/cooled rice and potatoes are very popular sources of resistant starch in the nutrition community because of their limited issues with digestion and because they also serve as a source of “safe” carbohydrates. In order to maximize the resistant starch content of rice, cooking long-grain rice with a rice cooker or by stir-frying 1-2 cups of cooked rice in 1-2 tbsp. of coconut oil—followed by 12-24 hours of refrigeration, will produce maximal amount of resistant starch.[fn value=9][/fn] Reheating your food will NOT destroy the resistant starch as long as the temperature does not exceed 140 degrees Fahrenheit. Additionally, adding an acidic dressing such as some type of vinegar to the rice or potatoes cooked in this fashion seems to also help enhance the resistant starch content and formation.[fn value=10][/fn]

• Pumpernickel bread
• Toasted or stale breads
• Potato starch
• Corn tortillas (Non-GMO)
• Corn flakes (Non-GMO)
• Rice square cereals
• Raw bananas
• Cooked plantains
• Uncooked rolled oats
• Cooked/cooled rice
• Cooked/cooled potatoes
• Cooked/canned white beans
• Cooked lentils

Clearly, not all of the included foods here are healthy choices. I would argue that the healthiest sources of resistant starch are cooked/cooled rice, and cooked/cooled potatoes, as these provide low glycemic index-carbohydrates and have little potential to contain anti-nutrients. I find it fascinating when foods that have long been part of traditional diets are found to have more health benefits than originally thought. Dishes made with cold rice or potatoes have been staple foods of many cultures, and as our understanding of the health supportive effects of consuming resistant starch expand, we see that there is more to these foods than simply serving as a source of carbohydrate.

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