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How Resistant Starch Affects Our Microbiota

Posted by Brad Dennis, Ph.D. on

How Resistant Starch Affects Our Microbiota

Almost all of the carbohydrates that we eat are starches. These long chains of glucose can be found in potatoes, grains, and many other foods. However, there are different types of starches, depending on their nutritional value, divided into three basic categories.

There is easily digestible starch, slowly digestible starch, and resistant starch that cannot be digested. This last type of starch goes through our digestive tract and remains completely unchanged. Over the last couple of decades, there have been many studies performed on resistant starch, as scientists want to find out what its properties are and what effects, if any, it actually has on our body.

How does resistant starch affect our gut?

One of the biggest reasons why resistant starch is the most important type is that it travels through our stomach completely undigested. In the end, it reaches our intestines and colon, in which it can “feed” all of the good bacteria that we have in our gut.

Scientists have discovered that our intestine holds hundreds of different types of bacteria. They are very beneficial to our gut health, and the greater the number of different types is, the better. The microbiota located in our intestines are key to regulating our gut health. The majority of the food we eat is good for feeding around 10% of the cells in our body, while resistant starches and fermented fibers feed the rest.

Resistant starch has been shown to have a positive effect on these bacteria, as it increases their number and the number of types that can be found within our gut.  The main reason why these starches have a positive effect on the bacteria is that they can increase the production of various short-chain fatty acids which are beneficial to the bacteria, including butyrate.

Resistant starch health benefits

There are many studies that show how both humans and animals can benefit from resistant starches, as they improve different metabolic features. A study with pigs as subjects, where they were fed resistant starch on a regular basis, showed that it had growth benefits.

A study on humans looked into how resistant starch affects people with type 2 diabetes. All of the 56 female subjects involved in this clinical trial showed that this supplementation reduced all the symptoms of their disease.

Beans have also been proven to improve insulin sensitivity and blood glucose control. The starchy substance inulin is already used commonly as a prebiotic, sugar substitute, fat substitute, and texture modifier, and it has a great role in improving gastric health.

Resistant starch is also helpful for treating cardiovascular diseases. Studies have shown that RS can reduce the risk of this type of disease in multiple ways. The β-glucan that you can find in barley or oats can greatly reduce the risk of coronary heart disease. Colonic experiments on animals, where they consumed red meat with added resistant starch, demonstrated that it was able to reduce some of the negative side effects of red meat and improve digestion.

A dietary treatment with resistant starch for patients who have type 2 diabetes, impaired fasting glucose or glucose tolerance, has been shown to reduce insulin resistance and fasting insulin, as well as overall insulin and glucose levels after a meal.

The unique effects of resistant starch on microbiomes

Our gastrointestinal tract has a microbiome that helps with the development and differentiation of our immune system. This microbiota system affects the way that our immune system will respond and be able to handle various infections and inflammatory diseases.

There are hundreds of different species of bacteria located in our intestinal microbiota. This system of bacteria has a much stronger and larger amount of metabolic capabilities and degradative enzymes than the host itself. Some of the most dominant species of bacteria have a lot of genes which can encode carbohydrate active enzymes, while being able to switch to multiple energy sources that they can find in the gut, depending on which ones are available. 

Another study has proven that resistant starches have a positive effect on microbiomes by increasing the amount of butyrate located in the large intestine. This study has shown that most of the people who participated had increased levels of butyric acid at the end of the experiment.

As mentioned before, resistant starch intake enhances the amount of butyrate that our gut microbes produce. Given the fact that butyrate functions as a strong anti-inflammatory substance for all the cells in the colon and improves our intestinal stability, it means that all of the toxins that are located in our gut are going to stay there and avoid spreading into the bloodstream, which can cause a lot of health issues.

Resistant starch has also been associated with reducing the risk of people getting colorectal cancer, as it has a couple of mechanisms that support colorectal health: DNA protection, positive gene expression changes, and increased cell death of precancerous or cancerous cells.

Possible side effects

Given the fact that all of these studies show that RS has a lot of potential for treating various health conditions, scientists also investigated the possible side effects of supplementing your food with RS. Early results have shown that resistant starch has no negative effects on our health.

Still, given the fact that RS supplementation is a major change in diet, it’s recommended that people who start begin with very small doses – just a quarter of a teaspoon per day. That amount can be increased gradually as time goes by. Users can expect bloating and increased gassiness; this is normal, as your gut microbiome will start to change, and your body will need to get used to those changes. These studies have calculated that a person will have to reach around 15 grams (or approximately 1 Tablespoon) of RS per day in order to experience the full effects.


These research studies have shown that resistant starch is a brand new food solution for improving health, and it works for both humans and animals. The overall health and number of your gut microbiota will improve, as will your digestive health, and your body will gain increased protected from certain diseases.


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