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Slices of a sweet potato on a cutting board alongside a whole sweet potato and a knife.

In the world of nutrition, there are few topics more hotly debated than carbohydrates and the “best” ways to get them. These philosophies range from low glycemic to carb cycling to the now well-known ketogenic diet.

You’ve probably also heard about the difference between simple carbs and complex carbs, and the benefits of a high-fiber, low-sugar approach.

Unfortunately, all the physiology jargon and debates have resulted in confusion and an all-out fear of carbohydrates for many. And while the “right” way to include carbs can vary from person to person — or even shift as your body composition or activity levels change — there’s one type of carbohydrate that most of us could stand to include more of in our diets: resistant starch.

A Simplified Lesson on Carbs

An entire series could be written about the structure, function, digestion, and metabolism of carbohydrates. Rather than provide what you can readily find in most physiology textbooks, here’s a quick overview on carbs to help make the information that follows about resistant starch more relevant:

Carbohydrates can be generally classified as simple or complex. Simple carbohydrates are quickly digested and absorbed, and are made up of one molecule (called a monosaccharide) or two molecules (called disaccharides). Complex carbohydrates, which are made up of many of these molecules, are called polysaccharides.

One type of polysaccharide is starch. Starch can be made up of amylopectin, which is quickly broken down and absorbed, and amylose, which is more slowly broken down and absorbed.

Generally, the more slowly starches are broken down and absorbed, the more they are referred to as “healthy” carbs. There is, of course, individual nuance to this, but we are speaking in broad terms here.

Each of the following factors can help slow down the speed of digestion and breakdown of starch:

  • Meal composition: Including fat, protein, and fiber alongside starchy foods can also slow down the digestion of starch due to the combination of foods being consumed at a meal. For example, toast consumed with eggs and avocado would break down more slowly than toast consumed by itself.
  • Soluble fiber: Found in beans, citrus, psyllium husk, and apples, soluble fiber dissolves in water and forms a gel. It’s the type of fiber you’ll see associated with helping to manage cholesterol levels.
  • Insoluble fiber: Found in nuts, beans, cauliflower, and berries, insoluble fiber can be thought of more as roughage and can help absorb water in the stool and aid in moving stool through the gastrointestinal (GI) tract.
  • Generation UCAN: A unique type of starch, this proprietary option is a polysaccharide that takes a long time to break down. It’s fully absorbed and provides a steady stream of glucose without spiking blood sugar. It’s a favorite among those looking to fuel workouts with steady energy or those trying to control food cravings due to blood sugar ups and downs.
  • Resistant starch: Comprised mostly of the slower-absorbed polysaccharide amylose, resistant starch (RS) resists breakdown and absorption in the upper digestive tract. This allows it to travel to the large intestine, or colon, in the lower digestive tract relatively untouched. Although it’s sometimes classified as a fiber in nutrition discussions — it has some of the same benefits of soluble fiber, in particular — resistant starch is not usually accounted for in the fiber content listed in foods.

A Closer Look at Resistant Starch

There are five subtypes of resistant starch, and foods can have a combination of them:

Type 1 is found in whole grains and seeds. Due to the protective properties of the outer layers of these foods, digestive enzymes are not able to reach the starch to break it down. 

Type 2 is high in amylose, which has a structure that makes it difficult for digestive enzymes to break down them down. Good sources of type 2 resistant starch include raw potatoes; unripe, green bananas; corn; and legumes.

Type 3 is sometimes called “retrograded” starch. When foods such as potatoes, oats, pasta, and rice are cooked and then cooled, type 3 RS forms.

Type 4 is made from chemical modification in food processing, normally from corn. It’s often added to processed foods to boost RS content.

Type 5 is when amylose forms a complex with a fat molecule called a lipid. It can act similarly to fiber; some food scientists are exploring ways to increase type 5 RS content in certain foods like rice.

As mentioned earlier, resistant starch travels through most of your upper digestive tract relatively untouched. Most of the functional benefits of RS are the result of how it acts once it reaches your lower digestive tract or colon.

Four Benefits of Resistant Starch

1. Digestive Health

In the colon (or large intestine), RS acts as a food for the beneficial bacteria, or probiotics, that live there. Any useful “food” for these probiotic bacteria are called prebiotics, and the prebiotics (which includes RS) ferment the “food” to help themselves thrive. (In fact, sometimes probiotic supplements taken orally along with RS can help the beneficial bacteria stick to the surface of the RS and better survive the trip through your digestive tract to eventually reach the colon.)

When these beneficial bacteria have more of the RS to ferment as a prebiotic, they can flourish, as well as produce beneficial compounds called short-chain fatty acids, or SCFAs. The short-chain fatty acids that are produced include acetate, propionate, and butyrate.

Butyrate production is boosted with ingestion of RS, providing fuel for the cells of your colon. It can help normalize the function of these cells, and even stimulate abnormal ones to self-destruct.

Butyrate can enhance blood flow to the colon, minimize inflammation, increase uptake of fluid and electrolytes, and support the regeneration of diseased lining in the gut. As a result, butyrate is the subject of a lot of research for its potential benefits in ulcerative colitis and possible benefits to colorectal-cancer risk. (Butyrate plays a surprisingly big role in overall health. Learn more at “The Health Benefits of Butyrate.”)

Resistant starch has also been shown to increase the weight and bulk of feces and help alleviate diarrhea.

2. Blood-Sugar Regulation

In mice, butyrate production as a result of higher resistant-starch intake has been shown to help make cells more sensitive to insulin by fighting insulin resistance. This helps keep blood-sugar levels more stable.

In humans, 30 to 40 grams of resistant starch per day has also been shown to clear sugar out of the bloodstream, even without a boost in insulin (the hormone that the body uses to lower blood sugar).

3. Appetite, Energy Balance, and Body Composition

While some studies on resistant starch’s effect on body composition show mixed results, there are some promising insights.

Eating more resistant starch, for instance, might help control the balance of calories consumed to calories burned. Due to the calories burned in the digestive process, RS is estimated to provide 2.5 calories per gram versus the 4 calories per gram provided by other starches.

As a bonus, resistant starch might also help you have more satiety and feel fuller compared to other starches, likely due to its suspected effect on certain appetite-regulating hormones, such as GLP-1 and PYY.

Studies looking directly at body weight generally show a net effect of resistant starch, though human studies do not take into account the fact that resistant starch increases the weight of stool in the GI tract. A few rodent studies confirmed that this could indicate that body weight (outside of waste) might be lower.

Compared to other starch, RS may also support lean-body mass and reduce fat storage in the deep, metabolically disruptive visceral fat.  

One summary stated:

“There is sufficient evidence in both humans and rats to suggest that, relative to [dietary starch] ingestion, [resistant starch] promotes fat oxidation, decreases carbohydrate oxidation, and prevents fat accumulation specifically in adipocytes.”

In other words, when comparing resistant starch to other starches, resistant starch might help the body burn fat instead of carbs and help control fat gain.

4. Cholesterol

Studies have shown that higher intakes of resistant starch — especially over four weeks or longer — can help lower both total cholesterol and the “bad” LDL-cholesterol. (Caveat: while keeping LDL-cholesterol levels under 100 mg/dL is a prudent goal, going too low in LDL may not necessarily be better.)

At higher doses, RS can even play a role in lowering triglycerides, which can be high from a caloric surplus, particular from high carbohydrate foods that raise blood sugar. 

How Much Resistant Starch Is Needed?

Most of the health benefits of resistant starch are shown at a dose of 30 to 40 grams per day or more. Unfortunately, the average person in the United States consumes only 3 to 8 grams per day, with the primary sources being from foods that are generally low in nutrients compared to their carbohydrate content, such as bread and cereal.

Similar to fiber, it’s important to work slowly to increase the intake of resistant starch. While it’s known to have fewer digestive side effects than fiber when increased quickly, it can still cause some discomfort if your rate of increase is faster than your body’s ability to adjust. Remember, resistant starch does a great job of feeding the beneficial bacteria in your digestive tract, so a quick increase results in more fermentation and gas production.

Here are a few ideas to help bolster your intake of resistant starch:

  • Sneak in more beans. For instance, toss some white beans into ham soup or black beans into dishes made with ground meat. Top salads with lentils, or enjoy homemade refried pinto beans with lime, garlic, and chili powder as side with your breakfast eggs.
  • Add uncooked oats to a post-workout shake or make this overnight oat recipe with coconut or almond milk.
  • Try to buy and use bananas when they still have a green tint to them. As they ripen and turn yellow, the resistant starch changes to regular starch and sugar.
  • Boost your intake of retrograded, type 3 resistant starch by tweaking your side dishes. Try a spin on potato salad: Combine cooked-then-cooled potatoes with salt, olive oil, Dijon mustard, and fresh herbs. Or try chilled pasta salad with veggies, basil, mozzarella and tomatoes instead of hot potato or pasta dishes. Bonus if you’re using a chickpea or lentil-based pasta.
  • Batch-cook oatmeal instead of making it daily. Use the cooked-then-cooled grain throughout your week and mix with a combination of whole foods, including healthy fats sources.
  • Experiment with raw potato flour and green banana flour. These are popular ways to quickly increase the intake of resistant starch. They can be sprinkled into protein shakes, on top of oatmeal, or mixed into other foods once they’re cooked. Be sure to take it slowly with these concentrated RS options to minimize digestive discomfort.

As you work toward a diet that is rich in whole and minimally processed a foods instead of highly refined and processed one, your RS intake will naturally increase from a boost in vegetables, fruit, nuts, beans, and seeds.

Wrapping Up

Despite being bombarded with seemingly conflicting nutrition information and confusion around carbohydrates, there’s a rule of thumb that is simple to go back to:

As much as possible, focus on balancing your plate with ample quality protein from fish, eggs, meat, and poultry; plenty of non-starchy, fibrous vegetable options; flavorful healthy fats such as olive oil, avocado, nuts and seeds; and carbohydrates that are close to their natural forms, such as beans, lentils, potatoes, and fruit.

Instead of fearing carbohydrates, focus on the types that are slow to digest and can work in your favor: high-fiber foods, specialized Generation UCAN energy starch, and foods that provide you with the many health benefits of resistant starch.

Samantha McKinney, RD, CPT

Samantha McKinney has been a dietitian, trainer and coach for over 10 years. At first, her interests and experience were in a highly clinical setting in the medical field, which ended up laying a strong foundation for understanding metabolism as her true passion evolved: wellness and prevention. She hasn’t looked back since and has had the honor of supporting Life Time’s members and nutrition programs in various roles since 2011.

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