- Resistant starch is a special type of carbohydrate that is not digested in the small intestine, but reaches the large intestine, where it serves as food for beneficial intestinal bacteria.
- Regular consumption of resistant starch can help lower blood sugar levels, improve digestion, reduce the production of inflammatory factors and promote gut health by producing short‑chain fatty acids, especially butyrate.
What is resistant starch?
Resistant starch is the part of starch that resists digestion in the small intestine and passes undigested to the large intestine, where the gut microbiome ferments it, similar to fibre. This fermentation produces short‑chain fatty acids (SCFAs), especially butyrate, which positively affects the intestinal lining and overall health.
Each type has a different structure and health effects and may respond differently to food processing. Resistant starch can be found in various fresh and processed foods, but the amount can vary considerably depending on the processing method, temperature, water content or storage time.
Based on their physical and chemical properties, resistant starches are divided into five types:
- RS1 - physically inaccessible starch, surrounded by plant cell walls (e.g., whole cereals, seeds, legumes).
- RS2 - native starch with a crystalline structure resistant to enzymes (e.g., green bananas, raw potatoes).
- RS3 - so‑called retrograded starch, which is formed when starchy foods are cooked and then cooled (e.g., cooled rice, potatoes or pasta).
- RS4 - chemically modified starch resistant to digestion (added to foods as a functional ingredient).
- RS5 - complexes of starch with lipids or other molecules (e.g., proteins or polyphenols) that significantly increase resistance to enzymatic degradation.
What are the health benefits of resistant starch?
Resistant starch works a little differently in the body than regular carbohydrates—instead of being absorbed quickly and raising blood sugar levels, it travels to the large intestine, where it becomes "food" for beneficial bacteria. Because of this, it can have a number of positive effects on our health.
1. Supporting a healthy digestion and the microbiome
Resistant starch behaves similarly to fibre in the gut. It is not digested in the small intestine but only in the large intestine, where gut bacteria ferment it. These bacteria produce substances such as butyrate, which:
- nourish intestinal cells,
- can reduce the production of inflammatory markers,
- improve the intestinal environment (for example, by lowering the pH, which helps prevent the overgrowth of harmful bacteria),
- and can also help with constipation or irregular bowel movements.
For example, in one meta‑analysis of studies, people who ate more resistant starch had higher stool volume and more beneficial bacteria such as Bifidobacterium and Faecalibacterium.
2. Helps with blood sugar
Resistant starch breaks down slowly, so it doesn't cause spikes in glycaemia after eating. It may therefore be helpful for people with type 2 diabetes, prediabetes or insulin resistance.
Results of some studies:
- People with diabetes who took RS2 had a lower glycaemic response and insulin levels after meals and fasting.
- The effect was strongest at a dose of 20–40g per day and in overweight people.
- There was also a long‑term reduction in Hba1c (glycated haemoglobin). Glycated haemoglobin is the best indicator for assessing glycaemia in the long term. A lower value also means a lower glycaemic response after a meal.
3. It may reduce the production of inflammatory substances
Chronic inflammation is involved in many diseases, from diabetes to cardiovascular disease. Some types of resistant starch (mainly RS2) have been shown in research to help reduce levels of inflammatory substances in the body, for example:
- TNF-α and IL‑6 - inflammatory molecules associated with insulin resistance
- CRP - a marker of overall inflammation (reductions have been seen mainly in people with diabetes)
- There was also an overall increase in the body's antioxidant capacity
The effect was greater when people consumed more than 20 grams of RS per day for at least 6 weeks.
4. It helps with lowering "bad" cholesterol (LDL)
Some research shows that resistant starch (especially RS2) can slightly lower total and LDL cholesterol, the latter of which is associated with a higher risk of cardiovascular disease.
- In studies, people who took RS had several units lower total and LDL cholesterol than those who did not.
- Again, the effect was more potent at higher doses (20g or more) and with longer durations of use (4 weeks or more).
5. May help with satiety and weight
Because resistant starch digests more slowly and ferments in the intestines, it can:
- increase satiety after meals,
- reduce cravings for sweets or extra portions,
- and, in some people, even contribute to a slight weight loss.
For example, one study showed that people who consumed biscuits with added resistant starch felt fuller for longer than after eating conventional biscuits. However, the effect of resistant starch on fat reduction is inconsistent, and it cannot be said that increased intake will promote weight loss.
How many grams of resistant starch should we eat?
There is currently no official recommended daily allowance of resistant starch, as there is for fibre (25–30g/day). Nevertheless, research shows that a certain amount needs to be taken in for health effects, often more than the normal diet provides.
How much do we normally take in?
In Europe, the average daily intake of resistant starch is around 3‑6g. In China, it is as high as 15 g/day, and in some African regions, as high as 30g/day, mainly due to the higher consumption of rice and pulses.
What are the proven benefits?
According to available studies, the health effects of resistant starch depend on the amount in the diet:
- 10‑20g/day - can aid digestion and slightly affect glycaemia.
- 20‑40g/day - can have stronger effects, such as reducing blood sugar levels and inflammation or improving the health of the microbiome.
- Some clinical studies have used doses above 40g/day, especially when testing specific dietary supplements or functional foods.
To give you an idea...
- 100g of cooled cooked rice contains approximately 2‑3g of resistant starch.
- 1 green banana can contain up to 4‑5g of RS.
- Special foods fortified with RS (e.g. with added HI‑MAIZE®) may contain more than 5 g RS per serving.
What to watch out for when increasing intake
If you are not used to a higher intake of fibre or resistant starch, it is recommended to start slowly — that is, with smaller amounts (e.g., 5–10 g per day) and gradually increase. Suddenly introducing a high dose may cause bloating, flatulence or changes in bowel movements in more sensitive individuals — but this is a normal adaptation of the gut microbiome and usually resolves after a few days.
Resistant starch foods
Resistant starch can be found in a variety of natural and processed foods, but the amount can vary significantly depending on the processing method, temperature, water content or storage time. Below is an overview of the richest sources, along with simple tips on using them in practice.
1. Oatmeal
Oats are one of the best ways to increase your intake of resistant starch.
- 100g of cooked oatmeal contains approximately 3.6g of RS.
- Let them cool after cooking or stand overnight—this will increase the resistant starch content even more.
For example, prepare 'overnight oats' — oatmeal soaked overnight in milk or yoghurt.
2. Cooked and cooled rice
Rice is affordable and suitable for preparing in bulk.
- It is best to boil the rice, let it cool (e.g., overnight), and then reheat it or use it in salads.
- Brown rice also has more fibre, magnesium and other minerals than white rice.
For example, prepare a portion several days in advance — you will save time and increase the resistant starch content..
Watch out when cooling rice. In general, it is advisable to cool rice quickly and not leave it at room temperature for long periods. Rice can sometimes contain Bacillus cereus bacteria, which, if the conditions are right, can start to grow after cooking and produce toxins that may cause food poisoning or indigestion.
3. Other whole grain cereals
Whole grain cereals such as barley or sorghum are great sources of RS and fibre. In addition to RS, they also contain B vitamins, selenium and other antioxidants.For example, replace your usual side dish once a week with barley groats.
4. Legumes
Legumes such as beans, lentils, peas or soybeans contain naturally high amounts of RS (about 1–5g per 100g cooked). Add legumes to soups and salads or use them as a major protein source in meatless meals.
5. Boiled and cooled potatoes
Potatoes that are left to cool after cooking significantly increase their RS content. Let them sit for at least a few hours (ideally overnight in the fridge) and use them in potato salad or roast them the next day — the RS is retained.
6. Green bananas
Unripe bananas (green) contain a lot of RS2. As the banana ripens, the starch changes to simple sugars — the greener the banana, the more RS.
If you buy a green banana and want to preserve its RS content but don’t get to eat it, you can freeze it. The RS will remain the same amount during the freezing period.
7. Potato starch (raw)
Raw potato starch contains up to 80% RS. Just 1–2 tablespoons a day can be added to yoghurt, smoothies or overnight oats. It naturally thickens the food.
Important: Do not cook it — high temperatures degrade RS. Start with smaller amounts and monitor your digestive response.
8. Hi‑Maize (resistant starch from corn)
Hi‑Maize is a special type of corn starch that contains 40–60% RS. It is commonly added to a variety of foods (baked goods, cookies, beverages), but can also be purchased on its own. Add a spoonful to porridge, smoothies or homemade baked goods.
9. Other starchy foods (after cooling)
By cooking and then cooling, you can also increase RS in foods such as pasta or sweet potatoes.
Prepare a larger batch of side dishes on the weekend, let them cool and use them throughout the week.
Bottom line
Resistant starch is an interesting food component that is often overlooked. Yet, based on dozens of high‑quality studies, it has proven effects on various aspects of health:
It promotes healthy digestion and the nourishment of intestinal cells through butyrate production.
It improves the composition of the gut microbiome, in particular increasing the amount of beneficial bacteria.
It helps reduce post‑meal glycaemia and may also reduce fasting sugar levels in the long term, especially in people with type 2 diabetes or metabolic syndrome.
In some cases, it reduces inflammatory markers and LDL cholesterol levels.
It may promote satiety and, in some people, contribute to weight loss.
The good news is that you don’t need to look for resistant starch in specialised supplements — you just need to adapt your regular foods: for example, eat cooked and cooled rice, potatoes or pasta, and include more legumes, whole grains or green bananas. With a little planning, increasing your daily RS intake is easy without radical changes to your diet.
