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Medically reviewed by Elizabeth Barnes, RDNMedically reviewed by Elizabeth Barnes, RDN
Carbohydrates are categorized based on their chemical structure and how the body digests them. Starches are complex carbohydrates composed of multiple units of glucose, or sugars, bonded together. Starches serve as the primary carbohydrate source in most people's diets.
Compared to simple sugars, starches take longer for the body to digest as they must be broken down into single sugar units to be absorbed and used for energy.
Most starches are naturally found in foods like legumes, grains, and potatoes. Manmade sources of starch, such as maltodextrin, are also used in commercial food production and home cooking and are sometimes taken as dietary supplements.
Types
Starches are separated into three groups based on their digestibility, or how quickly they're broken down into glucose, a type of sugar your body uses for energy. Starches must be broken down into glucose before your body can absorb them and use them as a fuel source.
Rapidly Digestible Starch (RDS)
Rapidly digestible starch is broken down into glucose within 20 minutes. This type of starch has a significant affect on blood sugar and can cause a rapid rise in blood glucose levels soon after they're consumed.
RDSs provide a quick source of energy, which may benefit specific populations, such as athletes.
Slowly Digestible Starch (SDS)
Slowly digestible starch is turned into glucose within 20-120 minutes. This starch is more slowly digested, which leads to a slower rise in blood sugar after eating compared to RDS.
SDS is generally considered more beneficial for overall health than RDS because it has less of an effect on blood sugar levels and may reduce the risk of health conditions like diabetes.
Resistant Starch (RS)
Resistant starch resists digestion for at least 120 minutes. Unlike other starches, RS passes through the small intestine undigested into the large intestine, where the gut bacteria break down and ferment the starch.
Resistant starch is further divided into four subcategories:
Resistant starch type 1 (RS1): RS1 is found in foods like whole grain bread, seeds, and legumes.Resistant starch type 2 (RS2): RS2 is concentrated in raw potatoes and green bananas.Resistant starch type 3 (RS3): RS3 forms when certain starchy foods, like potatoes and rice, are cooked and then cooled.Resistant starch type 4 (RS4): RS4 is a manmade starch derived from potato, corn, or tapioca starches.
Similar to SDS, resistant starch is considered better for health than RDS because it has a less significant effect on blood sugar levels.
Benefits
Starches provide an important source of energy and may support health in other ways, too.
Rapidly Digestible Starch (RDS)
Rapidly digestible starches provide a quick energy source and rapidly increase blood sugar levels, which can benefit people who need an easy fuel source during intense activity.
Athletes sometimes use RDS supplements to enhance exercise performance.
When taken as a supplement, fast-digesting modified starches, such as Vitargo®— a supplement derived from corn starch—have been shown to improve exercise performance and replenish levels of glycogen, the storage form of glucose, in muscles.
Carbs with rapid absorption rates and high glycemic indexes (GIs) like maltodextrin—a rapidly digested carb derived from starches like corn starch—are sometimes taken by athletes before or after workouts to increase energy levels and support post-exercise muscle recovery.
For example, maltodextrin is a common ingredient in sports performance supplements, like energy gels, which are commonly used by runners and other competitive athletes.
Slowly Digestible Starch (SDS)
Slowly digestible starches in foods like root vegetables, grains, and legumes are digested more slowly than RDSs.
For most people, SDSs are a better choice than RDSs, as they lead to a slower, more consistent rise in blood sugar. Foods that contain SDS have less of an effect on both short and long-term blood sugar control and could help protect against the development of conditions associated with elevated blood sugar and insulin levels, such as type 2 diabetes and heart disease.
Choosing foods that contain SDS over more rapidly digested carbs can also increase satiety and improve blood sugar control in people with existing health conditions, like diabetes. SDS reduces post-meal blood sugar surges, improving overall glycemic control and reducing the need for diabetes medications like insulin.
Eating more slowly digested carbs, like foods high in SDSs, also leads to a more consistent, slower rise and fall in blood sugar levels, which helps support more sustained energy levels and better mental performance.
Resistant Starch (RS)
Resistant starch differs from RDS and SDS in that it passes through the small intestine intact. This is because RSs are resistant to the action of digestive enzymes and are not digested in the small intestine.
This allows RS to travel to the large intestine, where gut bacteria ferment the starch. This fermentation process produces short-chain fatty acids (SCFAs) like butyrate, acetate, and propionate.
SCFAs positively affect health in several ways. They help maintain the integrity of the intestinal barrier, act as a fuel source for the cells lining the large intestine, regulate inflammation and PH levels in the gut, and support mucus production, all of which are essential to digestive health.
In addition to gut health, SCFAs affect appetite regulation, immune response, cellular function, and sleep, which is why consuming foods that increase the production of these compounds is so important.
Because RS has been shown to be effective in regulating inflammation, reducing appetite, and improving the overall health of the gut, diets high in RS may help protect against common diseases such as inflammatory bowel disease (IBD), diabetes, and obesity.
Eating foods rich in RS, such as RS3, may be particularly beneficial for people with high blood sugar levels. Studies show that consuming foods high in RS3, like cooked and cooled rice, results in a lower post-meal blood sugar spike in people with diabetes compared to freshly cooked rice. This is because the cooling process reduces the content of available carbohydrates in food by turning the carbs into resistant starch, reducing the food's effect on blood sugar.
Sources of Starch
Starches are found in several foods. Some of the most common sources of starch include:
Starchy vegetables, like potatoes, acorn squash, and sweet potatoesCorn and corn productsLegumes, such as peas and black beansGrains, such as wheat, rice, and barleyGrain products, such as bread, cereal, and pastaStarchy snack foods like potato chips, crackers, and cakes
You can also purchase manmade starches derived from starchy foods like potatoes and corn to use in your home cooking. Certain manmade starches are also used as dietary supplements and as ingredients in commercial food production.
For example, maltodextrin is a starch product used to improve the taste and texture of pre-packaged foods. Maltodextrin is sometimes taken as a sports performance supplement by athletes and people looking to boost their exercise or gym performance.
RS3, also known as “retrograded starch,” is not found in raw foods. It's formed when foods like potatoes, rice, and pasta are cooked and cooled.
How To Incorporate Starch Into Your Diet
Most people benefit from adding foods high in SDS and RS, such as complex carbs like root vegetables, whole grains, and legumes, to their diets.
These sources of starch can easily be incorporated into an overall healthy diet and can help improve your health when they replace more refined carbohydrate sources, like white bread and sweets.
Though refined grains, like white pasta and white bread, also contain starch, they lack the beneficial nutrients concentrated in complex carbs, such as fiber, vitamins, and minerals.
This is why most health organizations recommend choosing complex starch sources over refined carb sources.
Your carbohydrate needs depend on factors like your activity levels, body size, and underlying health conditions. The Dietary Guidelines for Americans recommend between 45-65% of your daily calorie intake comes from carbohydrates, like starches. However, some people may follow lower-carb diets for various health reasons.
Side Effects
Starch is an important source of energy in most people's diets. However, choosing the most beneficial types of starch is essential.
Eating too many refined and rapidly digested starch sources can negatively affect health. These starches are quickly absorbed by the body and lack satiating nutrients like fiber. They can lead to increased short and long-term blood sugar, which can raise the risk of developing health conditions like obesity and type 2 diabetes.
Eating too many starchy foods, like potato chips, sweet baked goods, and white bread, can also negatively affect blood sugar control in people with existing health conditions like prediabetes and diabetes.
Aim to choose foods rich in SDS and RS over more refined starch products most of the time. However, some people, such as athletes, may need to consume more rapidly digested sources of carbs.
In some cases, people with certain health conditions may need to limit their starch intake. For example, people with Congenital sucrase-isomaltase deficiency (CSID), a rare condition that affects the body's ability to digest carbohydrates like starches, must follow a starch-free or low-starch diet to control symptoms such as diarrhea and bloating.
People with very high blood sugar and elevated heart disease risk factors, like high triglycerides, may also benefit from limiting starches in their diet.
A Quick Review
Starches are carbohydrates that provide an important source of energy in the diet. There are several types of starches, which differ in terms of their digestibility and effect on blood sugar.
Though all starch types have important uses, most people can benefit from choosing slower digesting starches, like beans, starchy vegetables, and whole grains, over more rapidly digested starch sources, as they're linked with the most health benefits.
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