Why You Should Eat Resistant Starch for a Healthy Microbiome

Starch Is Naturally Eaten by Bacteria

Many scientists think of the complex ecosystem of microbial organisms in our intestines as an entirely separate and important organ within the body.^[1] The millions of organisms that ideally live in harmony in our gut require a sufficient supply of food, referred to as “Microbiota-Accessible Carbohydrates” or MAC.^[2] Microbiota-Accessible Carbohydrates consist of fiber or resistant starch. Resistant starch is a special type of fiber in carbohydrate-containing foods that is difficult for the small intestines to break down and use as energy.

Starch Is Metabolized by the Microbiota in the Gut

Resistant starch is fermented by the microorganisms in the intestines to further promote their growth. In fact, approximately 60% of the bulk of our stool is gut bacteria.^[3] This explains why even a slight increase in dietary fiber can significantly increase the mass and frequency of bowel movements. If we do not eat enough resistant starch/fiber in our diets, we are essentially starving our beneficial microbial co-inhabitants.  

Resistant starch is metabolized by microbes in the gut to produce molecules called short chain fatty acids, such as acetate, butyrate, and propionate. These short chain fatty acids have significant health benefits, including cancer fighting benefits and anti-inflammatory effects.^[4,5] Diets high in resistant starch lead to higher levels of short chain fatty acids and may offer protection against colon inflammation and disease.^[6] The dietary fiber that is fermented by our gut microorganisms is referred to as “prebiotics,” leading to the production of beneficial short chain fatty acids and other molecules, including serotonin and deoxycholic acid.^[7,8]

Eating resistant starch may even improve problems with insulin regulation, including insulin resistance and diabetes.^[9] Some skin diseases, including acne vulgaris, rosacea, and hidradenitis suppurativa are associated with insulin resistance.^[10-12] It is plausible that higher dietary intake of resistant starch and subsequent improvement in insulin resistance may alleviate symptoms in these skin conditions. However, more clinical research is required to evaluate these possible connections.

Healthy Foods Contain Resistant Starch

Even after just one serving of resistant starch, the microbial composition of our gut microbiome begins to diversify to contain more of the bacteria that eat resistant starch and away from a predominance of pathogenic and harmful microbial species.^[13,14] Unfortunately, the Western diet is relatively low in resistant starch and fiber and high in saturated fat and refined carbohydrates, leading to gut dysbiosis. In order to improve gut homeostasis and fruitful growth of beneficial bacteria, try to incorporate foods high in resistant starch into your daily diet.