Fiber Science . Research

What Is Resistant Starch? Types, Foods and What the EU Allows

November 3, 2026 · 7 min read
What Is Resistant Starch? Types, Foods and What the EU Allows
TL;DR

Resistant starch is starch that the small intestine cannot digest, so it reaches the large bowel and gut bacteria ferment it. It is found in beans, whole grains, green bananas, high-amylose maize and starchy foods that were cooked and then cooled. The EU allows one health claim: replacing ordinary starch with resistant starch, so that it makes up at least 14% of the starch in a food, gives a smaller rise in blood sugar after the meal. Adding resistant starch on top of a meal did not show that effect. In people, trials did not find that it raises the body's own GLP-1.

Resistant starch is starch that your small intestine cannot digest. It passes into the large bowel, where gut bacteria ferment it, so it counts as fiber. It is found in beans, whole grains, green bananas, high-amylose maize, and starchy foods that were cooked and then cooled.

The EU allows one health claim for it, about blood sugar after a meal, and only when resistant starch replaces ordinary starch in a food.

→ Read: Types of fiber supplements compared

What are the types of resistant starch?

Starch resists digestion for different reasons, and each reason is a type. EFSA, the EU food safety agency, described four in 2011:1

  • RS1 is locked inside plant cells or whole grains, so digestive enzymes cannot reach it. Beans, lentils and coarse whole grains contain it.
  • RS2 is raw starch packed into tight granules. Green bananas and high-amylose maize contain it. Most supplement trials use high-amylose maize, which is 50% to 90% amylose.1
  • RS3 forms when cooked starch cools and its chains pack back together. Cooked and cooled potatoes, rice and pasta contain it.
  • RS4 is starch that has been chemically changed so that it digests less.

Later reviews add a fifth type, RS5, where starch is bound to fat.2 Types 1, 2, 3 and 5 occur in food; types 2, 3 and 4 are also added to foods as ingredients.3

Resistant starch does not form a gel. Most of what it does happens when gut bacteria ferment it in the large bowel.4 Psyllium husk behaves differently: it thickens into a gel and is mostly not fermented.

How is resistant dextrin different?

Resistant dextrin is a different ingredient made from the same raw material. Starch is broken down and the pieces are rejoined with bonds the small intestine cannot digest. The result is a powder that dissolves clear and stays thin in water.5

Wheat dextrin, sold as Benefiber in the US, is one. Fibersol and Promitor are made from corn, and the NUTRIOSE name covers corn, wheat and pea versions.5 Some reviews group these powders with resistant starch, so the two terms are often mixed up. Our page on wheat dextrin covers that fiber in detail.

Comparison matrix of resistant starch, resistant dextrin and psyllium husk across three properties. Psyllium forms a gel in water; resistant starch and resistant dextrin do not. Resistant starch and resistant dextrin are broken down by gut bacteria; psyllium mostly is not. Only resistant starch holds an authorised EU health claim under its own name.

Resistant starch and resistant dextrin both come from starch and are both fermented. Only resistant starch holds an authorised EU claim, and only when it replaces ordinary starch in a food. Sources: EFSA Journal 2011;9(4):2024; Snelson et al., Nutrients 2019; Mysonhimer and Holscher, Advances in Nutrition 2022; EMA ispaghula husk monograph; Commission Regulation (EU) No 432/2012; EU Register of nutrition and health claims.

PropertyResistant starchResistant dextrinPsyllium husk
Forms a gel in waterNoNoYes
Broken down by gut bacteriaYesYesMostly not
Authorised EU health claim under its own nameOne (starch swap)NoneNone

Which EU health claim does resistant starch hold?

One. The EU wording is: “Replacing digestible starches with resistant starch in a meal contributes to a reduction in the blood glucose rise after that meal.”6 A food may carry it only if resistant starch has replaced ordinary starch so that it makes up at least 14% of the total starch.

The claim rests on an EFSA opinion that looked at 16 studies, mostly breads, muffins and snacks made with high-amylose maize in place of normal flour.1 The 14% figure comes from one of them: at least 11.5 g of resistant starch in a serving with 80 g of carbohydrate was needed before blood sugar rose less.

The effect comes from swapping some digestible starch for starch that is not digested, so there is less glucose to absorb. When resistant starch was added to a meal and the digestible carbohydrate stayed the same, it “does not appear to modify” the blood sugar response.1 So the claim belongs to a food made with less ordinary starch. It does not cover a powder stirred into a meal.

The EU refused two other claims for resistant starch: one on digestive health and “prebiotic” activity, and one on butyrate and colon metabolism. EFSA said both effects were too vaguely described to assess.7 Our explainer on how EFSA judges fiber claims covers what a refusal means.

Resistant dextrin holds no authorised claim under its own name. The EU register lists 14 refused submissions for wheat dextrin and 4 for Fibersol-2.7

What does the research on resistant starch show?

Most trials used high-amylose maize powder in small groups for a few weeks.

Blood sugar. A 2023 review of 36 trials in people with type 2 diabetes or prediabetes found smaller blood sugar rises after meals with RS1 and RS2, and lower fasting blood sugar with RS2.2 Two other reviews disagree on fasting blood sugar. One, of 19 trials, found a small drop of 0.09 mmol/L.8 Another, of 22 trials and 670 people, found no change in fasting blood sugar or HbA1c and called the benefit limited.4 They pooled different trials. Taken together, fasting blood sugar changes a little or not at all.

Cooled foods. In 15 healthy adults, white rice cooled for 24 hours and reheated held 1.65 g of resistant starch per 100 g, against 0.64 g when freshly cooked, and raised blood sugar less.9 In 30 women, 250 g of baked and chilled potato lowered blood sugar at 15 and 30 minutes, but the total rise was the same as boiled potato.10 A potato industry group funded that study.

Appetite. In the longest trial we found, 59 adults with prediabetes took 45 g a day for 12 weeks. Appetite, food intake and fullness hormones did not change.11

GLP-1. In people, the trials we found did not show resistant starch raising the body’s own GLP-1. The 12-week trial found no change.11 Two shorter trials found GLP-1 lower after a meal with resistant starch, likely because less glucose was absorbed.1213 The idea that it raises GLP-1 comes mainly from rodent studies.4 No trial has tested resistant starch in people taking a GLP-1 medicine.

Bowel and gut bacteria. A review of healthy adults found more stool weight, about 35 g a day, but no change in how often people went.14 Gut bacteria made more short-chain fatty acids in 16 of 23 trials that measured them.15 The response varied by person and by starch. In 174 young adults, potato starch raised butyrate by 29%, while high-amylose maize raised it by 5%, which was not significant. People who already carried certain bacteria responded more. Procter & Gamble part-funded that study.16

Insulin users. In 32 people with type 1 diabetes, cooled and reheated rice led to more low blood sugar episodes after the meal at a standard insulin dose: 12 against 3 with fresh rice.17 If you dose insulin by carbohydrate, talk to your diabetes team before changing your starchy foods.

How much resistant starch is tolerated?

Trials of resistant starch supplements used 8 to 66 g a day.4 Most of the trials that reported tolerance used 20 to 40 g a day, and in most of them people tolerated it.15 Gas can start lower: in one trial, 12 g a day of resistant starch or resistant dextrin for two weeks raised bloating and gas compared with a control, though the scores stayed low.5

There is no EU daily dose for resistant starch. The claim is a rule about the share of starch in a food. If you add any fiber, start small and build up slowly; our guide on starting a fiber supplement without bloating explains how. If you take a GLP-1 medicine, our page on taking fiber with a GLP-1 medication covers timing.

Who might resistant starch suit?

People who want more fiber from ordinary food. Beans, lentils, whole grains, green bananas and cooked-then-cooled starches all provide it.

People who find gel fibers hard to take. Resistant starch does not thicken a drink.

It is less suited to people who want help with constipation. In trials it added stool weight but did not change frequency. Psyllium has the stronger evidence for regularity.

Resistant starch is starch that feeds gut bacteria instead of being absorbed. Its one EU claim works by replacing ordinary starch, and it does not raise GLP-1 in the human trials so far.

Sources

Footnotes

  1. EFSA Panel on Dietetic Products, Nutrition and Allergies. “Scientific Opinion on the substantiation of health claims related to resistant starch and reduction of post-prandial glycaemic responses (ID 681), ‘digestive health benefits’ (ID 682) and ‘favours a normal colon metabolism’ (ID 783) pursuant to Article 13(1) of Regulation (EC) No 1924/2006.” EFSA Journal 2011;9(4):2024. doi:10.2903/j.efsa.2011.2024. Adopted 12 November 2010. Definition and types RS1 to RS4; high-amylose maize (50% to 90% amylose) is RS2; 16 relevant studies; the 14% condition from Behall and Hallfrisch 2002 (11.5 g RS2 in 80 g total carbohydrate); the effect is due to replacement of digestible carbohydrate, whereas adding RS2 “does not appear to modify” the post-prandial glucose response when glycaemic carbohydrate is kept constant. ↩ ↩2 ↩3 ↩4

  2. Pugh JE, Cai M, Altieri N, Frost G. Frontiers in Nutrition 2023;10:1118229. PMC10085630. Systematic review and meta-analysis: 36 RCTs, 982 participants with type 2 diabetes or prediabetes; five RS types including RS5 (starch–lipid complexes); no RS5 studies found. ↩ ↩2

  3. Patterson MA, Maiya M, Stewart ML. Journal of the Academy of Nutrition and Dietetics 2020;120(2):230-244. PMID 32040399. Narrative review: types 1, 2, 3 and 5 occur naturally in foods; types 2, 3 and 4 can be added as ingredients; cooked-then-chilled foods and high-amylose varieties contain more RS. ↩

  4. Snelson M et al. Nutrients 2019;11(8):1833. PMC6723691. Systematic review and meta-analysis: 22 RCTs, 670 participants, RS2 8 to 66 g/day for 1 to 12 weeks; no significant effect on fasting glucose, HbA1c or insulin resistance; RS does not form gels, its action relates to fermentation in the large intestine; rodent evidence on GLP-1 and PYY cited in the discussion. ↩ ↩2 ↩3 ↩4

  5. Mysonhimer AR, Holscher HD. “Gastrointestinal Effects and Tolerance of Nondigestible Carbohydrate Consumption.” Advances in Nutrition 2022;13(6):2237-2276. PMC9776669. Resistant maltodextrin/dextrin is soluble, fermentable and nonviscous, made from partially hydrolysed starch; NUTRIOSE (corn, wheat or pea), Fibersol and Promitor (corn). Stewart et al. 2010: 20 healthy adults, 12 g/day for 14 days of resistant starch, soluble fibre dextrin or soluble corn fibre raised bloating, cramping and flatulence versus maltodextrin, with low mean scores. ↩ ↩2 ↩3

  6. Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods, consolidated text of 20 August 2025, entry for resistant starch (ID 681, EFSA Journal 2011;9(4):2024). Condition: “The claim may be used only for food in which digestible starch has been replaced by resistant starch so that the final content of resistant starch is at least 14 % of total starch.” ↩

  7. European Commission, EU Register of nutrition and health claims, retrieved 3 November 2026. Resistant starch: ID 682 (digestive health, prebiotic) and ID 783 (normal colon metabolism, butyrate), both non-authorised as not sufficiently defined to be assessed. Wheat dextrin: 14 non-authorised entries. Fibersol-2: 4 non-authorised entries (post-meal glucose, bowel function, triglycerides, LDL cholesterol). ↩ ↩2

  8. Xiong K et al. British Journal of Nutrition 2021;125(11):1260-1269. PMID 32959735. Meta-analysis of 19 RCTs; fasting blood glucose −0.09 mmol/L (95% CI −0.13 to −0.04). ↩

  9. Sonia S, Witjaksono F, Ridwan R. Asia Pacific Journal of Clinical Nutrition 2015;24(4):620-625. PMID 26693746. 15 healthy adults; 0.64 g RS/100 g fresh, 1.65 g/100 g after 24 h at 4 °C and reheating; lower glycaemic response with the cooled rice. ↩

  10. Patterson MA et al. Nutrients 2019;11(9):2066. PMC6769955. 30 women with raised fasting glucose and insulin, 250 g baked-then-chilled vs boiled potato; glucose lower at 15 and 30 min; no difference in glucose area under the curve, GLP-1 or satiety. Funded by the Alliance for Potato Research and Education. ↩

  11. White U et al. Journal of the Academy of Nutrition and Dietetics 2020;120(6):1034-1041. PMC7247949. 59 adults with prediabetes analysed, 45 g/day high-amylose maize for 12 weeks; no effect on appetite, food intake, GLP-1, PYY or ghrelin. ↩ ↩2

  12. Bodinham CL et al. British Journal of Nutrition 2013;110(8):1429-1433. PMID 23507477. 30 healthy men, 48 g RS2; GLP-1 lower after breakfast. ↩

  13. Klosterbuer AS et al. Journal of Agricultural and Food Chemistry 2012;60(48):11928-11934. PMID 23136915. 20 healthy adults, 25 g fibre at breakfast; resistant starch with pullulan reduced glucose, insulin and GLP-1. ↩

  14. Shen D et al. International Journal of Food Sciences and Nutrition 2017;68(2):149-157. PMID 27593182. Meta-analysis in healthy adults: stool wet weight +35.5 g/day; stool frequency not significantly changed. ↩

  15. Sobh M et al. American Journal of Clinical Nutrition 2022;115(3):608-618. PMID 34871343. Systematic review: 39 RCTs, 2,263 participants; mostly RS2 at 20 to 40 g/day; SCFA production increased in 16 of 23 studies. ↩ ↩2

  16. Baxter NT et al. mBio 2019;10(1):e02566-18. PMC6355990. 174 young adults, 2 weeks; potato RS butyrate +29%; high-amylose maize RS +5% (not significant). Part-funded by Procter & Gamble. ↩

  17. Strozyk S et al. Nutrition & Diabetes 2022;12:21. PMC9013350. 32 people with type 1 diabetes; post-meal hypoglycaemic episodes 12 versus 3 at a standard insulin dose. ↩