What is Resistant Starch?

Resistant Starch is the new 'It' nutrient. Does this compound live up to its purported health benefits?

Resistant starch is a type of prebiotic fiber that cannot be digested by the body.

But that doesn't mean it's not broken down. Rather, an army of bacteria in our gastrointestinal tract ferments the starch into health-benefiting components.

What is Starch?

There are three primary types of carbohydrates: Sugar, Starch, and Fiber.

Sugar is the simplest form, made of just a single molecule that is broken down quickly and increases your blood sugar just as fast. These are the carbohydrates to have least often as they can negatively impact our health.

Fiber is a complex carbohydrate: the part of a plant that our body cannot digest. Fiber is found in the strong cell walls of the plant, and the types we usually eat are cellulose, hemicellulose, and pectin. Fiber helps us stay full, helps keep us regular, helps lower cholesterol, and provides many other benefits. These long-chain carbohydrates are broken down into metabolites by the bacteria in our gut, forming Short Chain Fatty Acids (SCFAs) that are important for our health.

Starch is also a complex carbohydrate, made of long chains of glucose polymers. They are usually found in starchy vegetables such as beans, potatoes, peas, and corn, as well as in cereal grain products such as bread, flour, oats, and barley. Some are digested quickly and some more slowly.

Most starches can be broken down by the body and used for energy (calories), however, resistant starch cannot. Because of this, resistant starch is classified as a fiber.

What is Resistant Starch?

Resistant Starch (RS) is the part of the starch molecule that cannot be digested in the small intestines and is instead fermented in the colon by bacteria.

There are four types of resistant starch:

Type 1: Found in seeds, legumes, grains, fruits, and vegetables, this type is surrounded by fibrous cell walls, making it indigestible.

Type 2: This type of RS is made of densely packed ungelatinized starch molecules. Having these granules so tightly aligned keeps them from being broken down by enzymes.

This type of RS is found in corn starch, raw potatoes, green bananas, and Jerusalem artichokes.

Type 3: Also called Retrograde starch, Type 3 RS is when starchy foods are cooked and cooled. The cooling process allows RS to develop. The swelling of the starch molecules (gelatinization) during heating 'deforms' the fiber so that we cannot break it down.

Foods that contain Type 3 RS when cooked and then cooled include potatoes, rice, beans, lentils, and oats.

Good news: Heating back up your already cooked-and-cooled food will not cause it to lose its resistant starch content!

Type 4 and 5: These are starch granules made more resistant by a man-made process.

What are the health benefits of Resistant Starch?

Research is finding more and more health benefits from including resistant starch in our diet.

Just like with other fibers, fermentation of resistant starch by bacteria in our gut forms short-chain fatty acids (SCFAs), including butyrate, acetate, and propionate.

These SCFAs are incredibly important to our health.

Here are just some of the health benefits resistant starch and SCFAs have been found to promote:

1. Digestion. SCFAs are the primary fuel source of the intestinal epithelial cells. These cells line the intestines and absorb the nutrients from digested foods. When fed ample SCFAs, these cells can stay healthier and more efficient at absorbing nutrients, electrolytes, and fluids.

   
   

2. Immunity. The intestinal epithelial cells also help keep harmful microbes from entering our bloodstream. Keeping these cells healthy and fueled with SCFAs helps them stay linked tighter together, strengthening the gut barrier and reducing the risk of harmful microbes getting into the bloodstream.

   
   

3. Gut microbiome. RS can help bolster the community of beneficial bacteria in our gut microbiome by providing a healthy medium for them to ferment and feed on.

   
   

4. Improved blood glucose levels. Some studies are showing that a diet high in RS may help improve insulin sensitivity and fasted blood sugar levels. This is because foods with a high RS content have less digestible starch and therefore a lower glycemic index, so they don't increase our blood sugar as much.

   
   

5. Improved insulin sensitivity and appetite regulation. SCFAs upregulate the expression of gut peptides such as glucagon-like peptide (GLP-1) and peptide YY (PYY), which help regulate appetite, glucose, and insulin homeostasis.

   
   

   GLP-1 helps make you feel more satisfied by suppressing glucagon secretion, delaying gastric emptying, and interacting with appetite-regulating centers within the hypothalamus and the brain. PYY also acts on our appetite-regulating centers.

   
   

   PYY also helps clear glucose from muscle and fat tissues.

   
   

6. May improve your lipid profile and impact how we burn fats. Since SCFAs that are unused in the gut will be absorbed and travel in the bloodstream, the RS we eat can have a wider impact. The SCFAs propionate and acetate are thought to play a role in lipid (fat) metabolism in the liver. Some studies indicate that these SCFAs may help increase the oxidation of fatty acids (more burning of fat) as well as reduce how much fat we store.

   
   

   Research shows that consuming RS may impact our lipid profile by helping reduce total cholesterol, LD cholesterol, and perhaps even triglycerides. Though, more studies are needed as the results are mixed.

How to include more Resistant Starch in your diet

There are many ways to help boost your intake of resistant starch daily - and no, it doesn't mean you have to eat raw beans! Blerg.

Batch-cook oatmeal.

Make a big batch of oatmeal, let it cool, and refrigerate for the week. Take out a portion each day and reheat with a bit of water or milk of choice to help with the texture. Add berries and nuts.

Eat green-ish bananas.

The bananas don't have to be fully green, but adequately underripe is the goal. Eat with a dollop of nut butter or slice into your previously-cooked-then-cooled oatmeal.

Cook a few sweet potatoes ahead of time.

By baking/roasting or boiling then mashing, letting cool, then refrigerating, you can enjoy these as high resistant-starch snack or part of a meal. Feel free to add your seasoning of choice!

Add raw potatoes to a salad

Shred raw sweet or white potatoes and sprinkle on your salad or chop into matchsticks and eat a small amount with hummus as a snack.

Raw potatoes in small amounts are perfectly safe to eat. Stick to around 1/4 to 1/3 cup to avoid a stomach ache. You can also use 1 to 2 Tbsp raw potato starch powder to add to a smoothie or yogurt.

Eat cooked beans twice per week

Other than resistant starch, beans and legumes provide us with many benefits. They are high in plant-based protein, fiber, and many vitamins and minerals. Beans have been shown to help improve glycemic control, reduce inflammation, improve your lipid profile, reduce blood pressure, and improve your gut health.

Batch-cook barley for the week

Be sure to purchase whole barley, not 'pearled' barley (which has had the outer, nutritious grain shell stripped away and is considered more refined).

Cook, cool, and refrigerate this high-nutrient grain for a quick add-on to your salads and meals.

Bottom Line

Resistant starch is an excellent addition to the diet and can improve our health in many ways.

Be sure to watch for symptoms as you add in different resistant starch-packed foods, as some of them (like raw potatoes) may cause gas and discomfort. Try smaller amounts if you find this an issue.

Note that when it comes to beans, the more consistent you are with eating them, the less these symptoms will persist!

As with increasing fiber, going too quickly may cause constipation. Begin including these foods in small amounts and slowly increase. Be sure to drink plenty of water as well!

Sources

1. National Research Council (US) Subcommittee on the Tenth Edition of the Recommended Dietary Allowances. Recommended Dietary Allowances: 10th Edition. Washington (DC): National Academies Press (US); 1989. 4, Carbohydrates and Fiber.

2. Bojarczuk A, Skąpska S, Khaneghah A, et al. Health benefits of resistant starch: A review of the literature. Journal of Functional Foods. 2022. Vol 93. Volume 93. https://doi.org/10.1016/j.jff.2022.105094.

3. Sajilata, M.G., Singhal, R.S. and Kulkarni, P.R. (2006), Resistant Starch–A Review. Comprehensive Reviews in Food Science and Food Safety, 5: 1-17. https://doi.org/10.1111/j.1541-4337.2006.tb00076.

4. Snelson M, Jong J, Manolas D, et al. Metabolic Effects of Resistant Starch Type 2: A Systematic Literature Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2019;11(8):1833. Published 2019 Aug 8. doi:10.3390/nu11081833

5. Topping DL, Clifton PM. Short-chain fatty acids and human colonic function: roles of resistant starch and nonstarch polysaccharides. Physiol Rev. 2001 Jul;81(3):1031-64. doi: 10.1152/physrev.2001.81.3.1031. PMID: 11427691.

6. Nogal A, Valdes AM, Menni C. The role of short-chain fatty acids in the interplay between gut microbiota and diet in cardio-metabolic health. Gut Microbes. 2021;13(1):1-24. doi:10.1080/19490976.2021.1897212

7. Walsh, S. K., Lucey, A., Walter, J., Zannini, E., & Arendt, E. K. (2022). Resistant starch—An accessible fiber ingredient acceptable to the Western palate. Comprehensive Reviews in Food Science and Food Safety, 21, 2930–2955. https://doi.org/10.1111/1541-4337.12955

8. Mullins AP, Arjmandi BH. Health Benefits of Plant-Based Nutrition: Focus on Beans in Cardiometabolic Diseases. Nutrients. 2021;13(2):519. Published 2021 Feb 5. doi:10.3390/nu13020519