Resistant Starch 101: A Complete Beginner’s Guide

You might have heard of starchy foods, like sweet potatoes, rice and other tasty carbs. But what is resistant starch, and why is it so good for your gut?

Many carbohydrate-rich foods contain starches, which are essentially long chains of glucose (sugar). Starchy foods range from highly refined, like tortillas and pasta, to whole grains and vegetables, like potatoes, plantains and carrots. Resistant starch is different. It isn’t a digestible carbohydrate, and it can radically transform your gut bacteria for the better.

Read on to find out how resistant starch works, how to consume it and all the ways to support a healthy gut microbiome.

What is resistant starch?

Resistant starch is a type of starch that’s “resistant” to digestion—your body can’t break it down. This type of starch is similar to dietary fiber because it can’t be fully digested.^[1]

Usually, digestive enzymes in your small intestine break down starchy foods and turn them into glucose. Starches consist of two types of polysaccharides called amylose and amylopectin. Foods that are higher in amylopectin are easily digestible starches. Meanwhile, foods high in amylose digest far more slowly.

Foods that are considered resistant starches are higher in amylose. Instead of being broken down like other carbs, resistant starch moves through the stomach and small intestine undigested, and arrives intact in the colon (the largest part of the large intestine).

Once the resistant starch arrives in the large intestine, your good gut bacteria feed on the starch and ferment it. Through that fermentation process, your gut bacteria produce something called butyrate (butyric acid).^[2]

Butyrate is a short-chain fatty acid that is an energy source for your enterocytes, or cells that line the GI tract.^{[3] [4]}

Fun fact: Grass-fed butter is a high-butyrate food, which is one reason why it’s such an important element in Bulletproof Coffee.

The benefits of resistant starch

Resistant starch acts more like a prebiotic than a typical starch.^[5] A prebiotic is what your good gut bacteria (probiotics) eat.

Along with strengthening digestive health by feeding all that good intestinal bacteria, there are several resistant starch benefits, including:

Reduces insulin resistance

Since resistant starch isn’t absorbed, your insulin doesn’t rise like other starches and cause blood sugar spikes. A 2012 study found that obese men who were given 15-30 grams of resistant starch a day for four weeks showed increased insulin sensitivity compared to a control group who took zero resistant starch.^[6]

Insulin sensitivity (aka low insulin resistance) is a good thing. If you have high insulin resistance due to chronically elevated blood glucose, you’re at risk of serious conditions like type 2 diabetes, metabolic syndrome, heart disease and obesity.^[7][8]

Burns fat and curbs hunger

Intake of resistant starch could help you control your weight. One study found that women who ate pancakes made with a resistant starch plus protein burned more fat after the meal than women who ate pancakes without resistant starch.^[9]

Another study found that adding resistant starch to meals could provide greater satiety, causing you to eat fewer calories.^[10]

Keeps you regular

If you deal with constipation, eating resistant starch may help get things moving again. A 2019 study found that resistant starch in the form of green bananas improved chronic constipation in children and adolescents.^[11]

Keep reading to look at the different types of resistant starch. In the meantime, if you’re looking for a gut health supplement that supports healthy digestion and contains collagen protein, check out new Bulletproof Gut Health Collagen Protein.

The types of resistant starch

There are four types of resistant starch, and some may work better for you than others. They include:

• RS1: This type of resistant starch is embedded in the coating of seeds, nuts, grains and legumes like lentils and beans. However, these foods don’t work for everyone: Gluten and grains contain varying amounts of inflammatory proteins and antinutrients that can affect people, even if they aren’t sensitive to gluten.
• RS2: Type 2 is the fermentable fibers in green bananas and raw potatoes.
• RS3: This type of resistant starch is made when some of the naturally occurring raw starches in white potatoes and rice are cooked and then allowed to cool.
• RS4: This is man-made resistant starch, or what you might see on a food label of a manufactured, processed food like bread or cake. The label might say polydextrin or modified starch. Man-made isn’t always a bad thing—one study found that a soluble fiber called resistant dextrin improved insulin resistance in women with type 2 diabetes.^[12]

The best sources of resistant starch

Foods high in resistant starch, like cooked and cooled white potatoes and legumes, aren’t ideal for people with certain dietary restrictions or food sensitivities. If you don’t eat nightshades or feel gastrointestinal side effects like bloating after eating legumes, pay attention to how you feel and adjust accordingly.

Here’s more detail about different foods you can use to create resistant starch recipes:

• Raw potato starch: Bob’s Red Mill Potato Starch is a good brand. To retain the resistant starch, don’t cook it—rather, dissolve the granules in cold or lukewarm water or a smoothie.
• Cooked and cooled white rice: The rice can be reheated—doing so won’t destroy the resistant starch.^[13] Try this recipe for cooled low-carb rice mixed with coconut oil.
• Green bananas and raw plantains (including green banana and plantain flours): When choosing bananas, go for the greenest ones, which are just unripe bananas. They might not taste as good, but they’re the highest in resistant starch. Try this recipe for White Chocolate and Raspberry Keto Cake that uses green banana flour.

How to introduce resistant starch into your diet

Some people respond well when they introduce resistant starch into their diet, while for others, it just doesn’t work. It can take six weeks or more for your body to get used to it, so start small. If you have too much, too soon, one of the tell-tale side effects of resistant starch is gas and bloating.

What about resistant starch, keto diets and carbs? Good news: Resistant starch is keto-friendly because it bypasses digestion, so it isn’t broken down like a typical carbohydrate—which means it won’t spike your blood sugar.

Here are some ideas to get started:

• Meal prep a batch of white rice at the beginning of the week. Cooling it will allow resistant starch to develop, and reheating doesn’t decrease the amount of resistant starch.
• Add one tablespoon of raw potato starch to no-cook foods, like smoothies and kefir. Heads up that white potatoes are nightshades and naturally contain higher levels of lectins, proteins which can contribute to inflammation, so pay attention to how you feel after having it.
• Blend green bananas or plantains into smoothies. If you can’t use them before they ripen, freeze them.
• Add green banana flour to desserts like No-Bake Protein Brownie Bites.

And remember, if resistant starch doesn’t work for you, you can also get get similar gut-friendly benefits with a prebiotic supplement.

How much resistant starch should you eat?

Although the estimated daily intake of resistant starch by Americans is about 5g per day, that’s far below the optimal amount. Actually, to obtain its health benefits, the recommended amount is a minimum of 6g per meal.^[14]

Can you eat too much resistant starch? Since it acts similarly to fiber in the body, you could experience minor gas and bloating if you eat higher levels of resistant starch.

Prebiotic and Probiotic Support

Bulletproof InnerFuel Prebiotic works as a prebiotic like a resistant starch to support healthy digestion and a thriving gut microbiome. If you’re worried about resistant starch on keto, InnerFuel is a great alternative because it’s keto-friendly. It’s also formulated to be super gentle on the digestive tract, which is great news for digestibility.

Even better: If you want prebiotics and probiotics all in one serving, plus collagen protein, reach for Bulletproof Gut Health Collagen Protein. It’s unflavored, so it’s an easy add-in for anything from coffee to smoothies.

Want to learn more about how to take care of your gut? Find out how to improve gut health and support your microbiome. For more details about different types of gut-friendly foods, like insoluble and soluble fiber, check out our guide to why fiber matters (and how to get more of it).

This article has been updated with new content.