A growing body of scientific research indicates that imbalances in the gut microbiota are associated with chronic health conditions such as diabetes, metabolic syndrome, obesity, and irritable bowel syndrome. To treat these health conditions, imbalances in the gut microbiota must be corrected. One way to accomplish this is by selectively feeding beneficial gut bacteria with prebiotics. Prebiotics are carbohydrates that are indigestible to humans and reach the colon intact, where they serve as fuel for gut bacteria. Resistant starch is a special type of prebiotic that has demonstrated great potential in the treatment of metabolic, digestive, and inflammatory disorders.
What is resistant starch?
Resistant starch is a type of dietary starch that is indigestible in the human digestive tract. This means that it reaches the colon intact (it “resists” digestion), where it feeds beneficial gut bacteria. This means that we humans do not obtain a significant amount of calories from resistant starch; rather, our gut bacteria receive the nutritive benefits.
There are four types of resistant starch (1):
RS (Resistant Starch) 1: This type of resistant starch is bound up in the cell walls of plants such as whole grains and legumes.
RS2: This starch is high in amylose, a polysaccharide that is indigestible in the raw state. However, RS2 does become digestible to humans when it is cooked, but this also removes the resistant starch health benefits. RS2 is found in unripe green bananas, potatoes, and plantains.
RS3: This is also referred to as retrograde resistant starch because it is formed when Type 1 or 2 RS is cooked and subsequently cooled. Heating the starch makes it digestible, but cooling it before eating causes the starch to revert back to the form that is most beneficial to our gut bacteria. Cooked and cooled white rice, potatoes, and legumes are included within this RS category.
RS4: This type of resistant starch is synthetic (such as “hi-maize resistant starch”) and is not recommended because it has not traditionally been a part of the human diet.
When you eat foods that contain one of these forms of resistant starch, the RS travels to the large intestine where bacteria digest the starch and subsequently create metabolites and have biochemical effects that improve our own health.
The health benefits of resistant starch
Increases levels of beneficial gut bacteria
Supplementation with resistant starch increases levels of Lactobacilli, Bifidobacteria, and Bacteroidetes, while decreasing levels of pro-inflammatory Firmicutes in the gut. (2) These bacteria produce short-chain fatty acids, such as butyrate, that support the health of enterocytes and have anti-inflammatory effects on the intestine.
RS increases levels of peptide YY and glucagon-like peptide (GLP-1) which may promote satiety and inhibit overeating. (3)
Improves insulin sensitivity and lowers blood glucose
In insulin-resistant subjects, RS supplementation has been found to improve insulin sensitivity. (4) Insulin resistance is a key component of metabolic syndrome, diabetes, overweight, and obesity, so the potential of RS to correct this underlying dysfunction is an exciting discovery!
Promotes weight loss
Resistant starch may increase the thermic effect of food, or the increase in metabolic rate after ingestion of a meal, thereby increasing the body’s total energy expenditure. It also increases the oxidation of fat for fuel and reducing fat storage in adipocytes (fat cells); together, these effects may promote weight loss. (5)
The health of the gut is intrinsically linked to the health of the entire body. By reducing inflammation in the gut through the production of butyrate and other anti-inflammatory substances, gut bacteria may also play a role in reducing systemic inflammation. For this reason, RS consumption may have a protective role against inflammatory diseases such as cancer. (6)
How to incorporate resistant starch into your diet
Here are some common food sources of resistant starch:
Green (unripe) bananas
This is personally my favorite form of resistant starch. I take it in the form of green banana flour. The brand I use is Zuvii Green Banana Flour, available below.
Cooked and cooled white rice, legumes, or potatoes
Bob’s Red Mill Unmodified Potato Starch.
I use the Organic Gemini Brand. While it is commonly used for gluten-free and Paleo baking, note that this flour must be consumed raw to obtain the RS health benefits.
I recommend starting with 1 tsp of resistant starch (if in the form of a flour) per day. If you are choosing to obtain resistant starch from plantains or cooked or cooled rice, legumes, or potatoes, I recommend trying ¼ to ½ cup at a time to start. If this causes gas, bloating, or generalized digestive upset, this may indicate that you have SIBO or intestinal dysbiosis. If this is the case, I would recommend first working on addressing the SIBO and dysbiosis first using dietary and herbal antimicrobial interventions. Resistant starch could then be slowly added in after gastrointestinal symptoms have started to improve.