Wonder Bread, cake, and noodles: Those are among the many highly digestible starches in American diets. Among their problems, researchers believe eating these rapidly digested starches could contribute to chronic disease including Type 2 diabetes. (1) Eating starchy foods regularly can also make you overweight.
“The average American consumes 133 pounds of flour a year in their food (down from 146.8 pounds in 1995); that’s more than a third of a pound per person per day, and some of us consume much more,” says Mark Hyman, MD, in Food: What the Heck Should I Eat?. “And that doesn’t include all the other grains and potatoes.” (Hyman wrote the forward to my book Align Your Health.)
He notes that our bodies were never meant to handle this much starch. “It’s a toxic drug dose that leads to obesity, heart disease, type 2 diabetes, dementia, and even cancer,” he says.
Yet like with most things, there’s an exception to every rule. And Hyman will be the first to tell you there’s an exception to the starch-will-make-you-fat-and-sick theory, called resistant starch.
Gut Health 101
To understand resistant starch, we need to back up a bit and understand the importance of gut health and its far-reaching implications on overall health.
“When I say it all starts in your gut, I mean almost everything!” says Vincent Pedre, MD, in Happy Gut. “Headaches, migraines, allergies, autoimmunity, weight gain, acne, skin rashes, yeast infections, hormonal imbalances, fatigue, immune challenges, even the way you sense pain—they all relate to the condition and health of your gut.”
Underlying gut health is your microbiome, a diverse ecosystem of bacteria that must stay in the correct balance. Maintaining healthy gut flora becomes crucial for nearly every system in your body, including your immune system. [Consider that about 70 percent of your immune system resides in your gut.] (2)
“We’re talking about more than five hundred different species of microorganisms residing in the human gut and totaling in the trillions…whose delicate balance not only influences gut function but also our overall health,” says Pedre. “A disruption in our gut flora then opens the door for unfriendly microbes to step in and take over.” He notes dysbiosis (or gut imbalances) paves the path for numerous gut conditions including intestinal permeability or leaky gut.
Lots of things can disrupt your gut-flora balance, including chronic stress, antibiotics overuse, and a bad diet. To rebalance your microbiome – to have that right balance of good flora that support a healthy gut and healthy body – demands the right diet, including plenty of fermented and cultured foods rich in probiotics.
These live microorganisms, found in foods including yogurt and kimchi but also in supplements, help create and restore a healthy balance among your gut flora. Research shows probiotics can benefit various diseases, ameliorate skin conditions, improve your immune system, and so much more. (3) In other words, probiotics can help restore gut balance.
Probiotics are living organisms, and they need something to feed on. Prebiotics are what probiotics eat. [All prebiotics are fiber, but not all fiber is a prebiotic.]. To be a prebiotic, it must resist small intestinal absorption, become fermented by your gut flora, and stimulate healthy gut flora. (4)
Prebiotics fall several categories, and each variety feeds a different type of gut flora. And that brings us to resistant starch, one of those prebiotic categories. (5)
What is Resistant Starch?
“Resistant starch is a form of fiber that is feasted upon by the good bacteria in your colon,” says Jonny Bowden, PhD, in The 150 Healthiest Foods on Earth. “That’s why it’s considered a prebiotic fiber—it’s food for the probiotics that live in your gut and that you want to thrive and survive.”
Put another way, resistant starch is a fermentable dietary fiber and the portion of starch your amylase enzymes (that break down carbohydrates) don’t break down in your small intestine. Instead, resistant starch heads to your colon, where gut flora ferment it. (6)
In Food, Hyman says two scientists discovered resistant starch in the 1980s after wondering why legumes, which are high in carbohydrate, don’t create a dramatic rise in blood sugar like other higher-carbohydrate foods do.
Here’s what they learned: Legumes are rich in what they termed “resistant starch,” because these starches resist digestion in your small intestine and don’t get metabolized as fat like other starches would.
According to Rudy Mawer, MSc, among the highest foods in resistant starch include oats, cooked and cooled rice, legumes, green bananas (sorry, once they ripen, the resistant starch turns to sugar), and cooked-then-cooled potatoes. (7) [For a more comprehensive list, scroll to the bottom of this article.]
Overall, Americans don’t eat these types of foods high in resistant starch. Instead, we eat fully cooked potatoes, rice, pasta, breakfast cereals, and bread, which are low in resistant starch. These highly digestible starches, which are low in resistant starch, raise your blood sugar and insulin levels. (1)
That’s unfortunate, since researchers find resistant starch offers both practical and health benefits. Resistant starch can easily replace regular starch in baked goods, reducing the caloric density and glycemic index in food.
Eating foods high in resistant starch can also benefit or improve various conditions including satiety (keeping you full for fewer calories), your lipid profile, insulin sensitivity, glycemic control, and metabolic syndrome. (8)
Let’s briefly look at a few of those benefits.
Resistant Starch for Gut Health
Most research on resistant starch focuses on gut health, particularly colon health. Your colon contains up to 1,000 different species of bacteria. This intestinal flora create energy by fermenting the carbohydrates not digested in your upper gut, including resistant starch.
When resistant starch beelines to your colon and your gut bugs fermented that starch, they produce several things including three short-chain fatty acids (SCFAs): Acetate, propionate, and butyrate. (4)
Among their benefits, research shows these short-chain fatty acids (SCFA) can positively impact intestinal barrier function, gut peptide secretion, and immune function. (9)
Butyrate is the key player here. This SCFA becomes the main energy source for your colon cells, (10) and Hyman says butyrate can also prevent cancer, speed up your metabolism, and reduce inflammation.
“Among its many roles, butyrate protects your intestinal barrier by dialing down potential gut problems like leaky gut,” says Pedre. “The SCFAs your colon cells don’t use head to your bloodstream and then liver where they provide additional anti-inflammatory benefits. When these colon bacteria ferment [resistant starch], they also boost good gut flora that crowd out the bad microbes, which can help with metabolism, mood, immunity, and weight management.” (11)
In other words, you want more butyrate, and a great way to get optimal amounts of this SFCA is to help your good gut bugs flourish with prebiotics including resistant starch.
“When your good bugs flourish, they can then replicate, producing vitamins, regulating your hormones, excreting toxins and creating healing compounds that keep your gut healthy and functioning properly,” says Hyman. “Bad bugs and yeast overgrowth, on the other hand, overload your system with toxins called lipopolysaccharides (LPS) that subsequently trigger inflammation, insulin resistance, pre-diabetes and ultimately weight gain.” (12)
Resistant Starch for Insulin Resistance and Diabetes
Resistant starch earns its limelight for gut health, but it carries other benefits, too, including stabilizing blood sugar (glucose) and insulin levels, making it an ideal staple for people with insulin resistance or Type 2 diabetes.
Insulin resistance “is an undesirable state of affairs that happens when the cells no longer pay attention to insulin,” say Bowden and Steven Masley, MD, in Smart Fat. “The cells, particularly the muscle cells, close their doors when insulin comes calling with its sugar payload. The sugar winds up going to the fat cells (and everyone knows how that story ends). Insulin resistance… is a hallmark of both diabetes and obesity, and a big risk factor for heart disease.”
A 2017 report from the Centers for Disease Control and Prevention (CDC) found over 100 million American adults are now living with diabetes or prediabetes, (13) and those statistics are only doomed to increase with our processed, sugary diet filled with quickly digestible starches.
One strategy to reduce insulin resistance that leads to pre-diabetes and Type 2 diabetes is to increase intake of high-fiber foods, including those with resistant starch.
Research shows eating foods with resistant starch results in lower post-meal glucose concentrations and subsequent insulin response compared with consuming foods containing ordinary starch. Additionally, eating fewer digestible starches may decrease glycemic response during a subsequent meal, which scientists call the “second meal effect.” (1)
Put another way: Resistant starch stabilizes blood sugar to reduce cravings, keep you full longer, and reduce the dramatic insulin spikes that lead to insulin resistance and eventually Type 2 diabetes.
Research verifies this. For patients with impaired fasting glucose, impaired glucose tolerance, or newly diagnosed Type 2 diabetes, resistant starch can reduce fasting insulin and insulin resistance and post-meal glucose levels. (14)
Another study – a single-blinded, randomized, parallel nutritional intervention with 20 insulin resistant subjects – found resistant starch treatment could improve insulin sensitivity, waist circumference, and fat storage. (15)
Resistant Starch and Chronic Disease
Beyond Type 2 diabetes, research is still emerging about resistant starch’s impact on various diseases, but a few studies show promise about resistant starch’s wide-ranging health benefits.
One found resistant starch improved colonic inflammation and enhanced growth of healthy intestinal bacteria in ulcerative colitis, making it a therapeutic option for people with chronic inflammatory bowel diseases. (16)
Another study found a high-resistant starch diet can slow down chronic kidney disease progression while improving oxidative stress and inflammation, both markers for many other diseases. (17)
Researchers find resistant starch might even impact cancer formation. One study looked at particular foods and breast cancer risk. They found certain resistant starch-containing foods – specifically, whole wheat bread, legumes, and boiled potato – might reduce breast cancer risk, whereas higher intake of white bread and biscuits could increase breast cancer risk. (18)
Resistant Starch for Fat Loss
Resistant starch can also help you lose weight. In Eat Fat, Get Thin, Hyman says it can help you get and stay lean by reducing insulin spikes after you eat, increasing fat burning, and reducing fat storage. (The same mechanisms that help people with insulin resistance and diabetes stabilize blood sugar levels.)
Research supports Hyman’s argument. Among other mechanisms, studies show resistant starch can increase satiety and lower your body mass index (BMI). (1)
Researchers believe resistant starch can help you lose weight via several variables:
- Lower calorie content – replacing rapidly digestible starch with resistant starch reduces the energy density of your diet.
- Increase satiety – you feel fuller for fewer calories.
- Increase energy expenditure or fat oxidation – replacing rapidly digestible starch with resistant starch may promote fat mobilization as the result of reduced insulin secretion. (1)
In one acute randomized, single-blind crossover study, researchers gave 20 healthy young adult males either 48 grams of resistant starch or a placebo between two mixed meals on two separate occasions.
Compared with the placebo, participants using resistant starch ate significantly lower amounts of food. Researchers concluded that 48 grams of resistant starch over a 24-hour period could help manage metabolic syndrome and appetite. (19)
Another one – this one an acute, randomized double-blind, crossover study – compared how four dietary fibers (including resistant starch) and a low-fiber treatment impacted satiety among 20 healthy participants. While researchers concluded that different types of dietary fiber impact satiety differently, resistant starch was a clear winner for keeping participants full. (20)
How to Get Resistant Starch
If you want to get the many benefits of resistant starch for weight loss, managing blood sugar, gut health, reducing your risk for disease, or all of the above, you’ve got a few ways to fit more into your diet. The most obvious: Increase foods high in resistant starch.
“Interestingly, the way you prepare starch-containing foods affects their starch content, as cooking or heating destroys most resistant starches,” says Mawer. “However, you can ‘recapture’ the resistant starch content of some foods by letting them cool after cooking.” (21)
I mentioned earlier that potatoes are a highly digestible staple in American diets, but it depends on how you prepare them. Cooked correctly, they can become a good source of resistant starch.
“If you’re going to eat [potatoes], cook and cool them first,” says Mark Hyman, MD, in Food. “You can gently heat them up again before digging in. The cooking and cooling creates resistant starch, which is good for your gut bacteria, helps your metabolism, and lowers the glycemic index of the food.”
One study showed cooling boiled potatoes overnight almost tripled their resistant starch. (22)
Researchers find the variety of potato you use doesn’t really matter. One study looked at three potato varieties (Yukon Gold, Dark Red Norland, and Russet Burbank, either baked or boiled at three temperatures. Researchers then analyzed starch content and found resistant starch content varied by cooking method and temperature but not variety. In other words, all three varieties had the same amount of resistant starch. (23) [White potatoes, notably, have more resistant starch than sweet potatoes.] (24)
An easier way to fit more resistant starch into your diet is with a supplement. You’ll typically find resistant starch as potato starch, which Mawer notes is the most condensed type of resistant starch. (21)
If you supplement, researchers find you can consume up to 50 grams of resistant starch without adverse effects, although experts urge caution in the beginning to start slowly and find your own tolerance. (4)
“Banish any notions that loading up on [resistant starch] will help you ditch 10 pounds by this weekend,” says Pedre. “Too much too soon will create miserable bloating, discomfort, and abdominal pain.” (11)
Hyman recommends using one to two tablespoons of potato starch in eight ounces of water once or twice daily. He recommends Bob’s Red Mill Unmodified Potato Starch (not potato flour), a potato starch contains that provides about eight grams of resistant starch per tablespoon. You might also add resistant starch to protein smoothies, coconut kefir, or coconut yogurt.
Athletes and Resistant Starch
If you’re any type of athlete – an endurance trainer, a CrossFitter, if you lift heavy – you probably utilize carbohydrates around your workout. How might resistant starch impact your workout?
Researchers find modifying starches creates varying metabolic and performance outcomes:
- Fast-digesting carbohydrates rapidly raise glucose and insulin levels, helping to restore glycogen stores following exercise (and potentially benefiting subsequent exercise).
- Slow digesting starches, on the other hand, blunt glucose and insulin response and increase utilization of free fatty acids (FFAs) during exercise, yet researchers find no effect on performance versus faster-absorbing carbohydrates. (25)
Everyone is different, so your results may vary cycling carbohydrates around your workout. In general, I recommend using resistant starch-heavy foods (or potato starch) before your workout. The slowly absorbing carbohydrate might help sustain energy during your workout. After your workout, incorporate more faster-absorbing carbohydrates, which may more easily replenish glycogen levels.
A Comprehensive List of Resistant Starch Foods
According to Alan Christianson, NMD, here are the top 30 sources of resistant starch:
- Raw oats
- Navy beans
- Northern beans
- Cannellini beans
- Adzuki beans
- Kidney beans
- Black beans
- Garbanzo beans
- Lima beans
- Pearl barley
- Green bananas
- Banana Peels
- Sushi rice
- Pumpernickel bread
- Rye bread
- Corn tortillas
- Sourdough bread
- Cooked millet
- Brown rice
- Rice pasta
- Pinto beans
- Hi-maize flour (26)
The Take-Home about Resistant Starch
I’m weary of overhyped ingredients that promise all sorts of health miracles, but resistant starch has enough research to substantiates its benefits for gut health, blood sugar management, and so much more.
Based on our evolving understanding about resistant starch, you might be able to fit more traditionally forbidden foods (such as white rice and white potatoes) into your plan, but that doesn’t give you license to overindulge in these foods. Too much can raise blood sugar and insulin levels, with all their repercussions.
If you’re curious, I suggest experimenting with resistant starch in small quantities: Say, try a small amount of white potatoes (properly cooked) during a meal. For someone extremely insulin resistant, even that small amount might create problems. Proceed accordingly.
As we learn more about the gut microbiome’s wide-reaching implications – as Pedre says, it can impact almost everything – you’ll want to implement a variety of nutrients including probiotics, dietary fiber, and prebiotics to support healthy gut balance.
Resistant starch isn’t a magic bullet to reverse Type 2 diabetes, restore gut health, or lose weight. But incorporated intelligently – worth repeating: Start slowly if you incorporate a resistant starch supplement – into a healthy eating plan that includes plenty of non-starchy vegetables, clean protein, and healthy fats, it might nudge the needle a little bit in your favor.