Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals. Resistant starch occurs naturally in foods but is also added to foods by the addition of dried raw foods, and isolated or manufactured types of resistant starch.
Some types of resistant starch (RS1, RS2 and RS3) are fermented by the large intestinal microbiota, conferring benefits to human health through the production of short-chain fatty acids, increased bacterial mass, and promotion of butyrate-producing bacteria.
Origin and history
The concept of resistant starch arose from research in the 1970s and is currently considered to be one of three starch types: rapidly digested starch, slowly digested starch and resistant starch, each of which may affect levels of blood glucose.
Resistant starch does not release glucose within the small intestine, but rather reaches the large intestine where it is consumed or fermented by colonic bacteria (gut microbiota). On a daily basis, human intestinal microbiota encounter more carbohydrates than any other dietary component. This includes resistant starch, non-starch polysaccharide fibers, oligosaccharides, and simple sugars which have significance in colon health.
The fermentation of resistant starch produces short-chain fatty acids, including acetate, propionate, and butyrate and increased bacterial cell mass. The short-chain fatty acids are produced in the large intestine where they are rapidly absorbed from the colon, then are metabolized in colonic epithelial cells, liver or other tissues. The fermentation of resistant starch produces more butyrate than other types of dietary fibers.
Modest amounts of gases such as carbon dioxide, methane, and hydrogen are also produced in intestinal fermentation. One review estimated that the acceptable daily intake of resistant starch may be as high as 45 grams in adults, an amount exceeding the total recommended intake for dietary fiber of 25–38 grams per day. When isolated resistant starch is used to substitute for flour in foods, the glycemic response of that food is reduced.
There is weak evidence that resistant starch can improve fasting glucose, fasting insulin, insulin resistance and sensitivity, especially in individuals who are diabetic, overweight or obese.  In 2016, the U.S. FDA approved a qualified health claim stating that resistant starch might reduce the risk of type 2 diabetes, but with qualifying language for product labels that limited scientific evidence exists to support this claim. Because qualified health claims are issued when the science evidence is weak or not consistent, the FDA requires specific labeling language, such as the guideline concerning resistant starch: "High-amylose maize resistant starch may reduce the risk of Type 2 diabetes. FDA has concluded that there is limited scientific evidence for this claim."
Plants store starch in tightly packed granules, consisting of layers of amylose and amylopectin. The size and shape of the starch granule varies by botanical source. For instance, the average size of potato starch is approximately 38 micrometers, wheat starch an average of 22 micrometers and rice starch approximately 8 micrometers.
|Starch granule characteristics|
|Starch||Diameter, microns (micrometers)||Granule Shape||Gelatinization temp, °C|
|Maize / corn||5-30||Round, Polygonal||62-72|
|Waxy maize||5-30||Round, Polygonal||63-72|
|High amylose maize||5-30||Polygonal, Irregular
|63-92 (not gelatinized in boiling water)|
Raw starch granules resist digestion, i.e., raw bananas, raw potatoes. This does not depend on the amylose or amylopectin content, but rather the structure of the granule protecting the starch.
When starch granules are cooked, water is absorbed into the granule causing swelling and increased size. In addition, amylose chains can leak out as the granule swells. The viscosity of the solution increases as the temperature is increased. The gelatinization temperature is defined as the temperature at which maximum gelatinization or swelling of the starch granule has occurred. This is also the point of maximum viscosity. Further cooking will burst the granule apart completely, releasing all of the glucose chains. In addition, viscosity is reduced as the granules are destroyed. The glucose chains can reassociate into short crystalline structures, which typically involves rapid recrystallization of amylose molecules followed by a slow recrystallization of amylopectin molecules in a process called retrogradation. 
Plants produce starch with different types of structure and shape characteristics which may affect digestion. For instance, smaller starch granules are more available to enzyme digestion because the larger percentage of surface area increases the enzyme binding rate.
Starch consists of amylose and amylopectin which affect the textural properties of manufactured foods. Cooked starches with high amylose content generally have increased resistant starch.
Definition and categorization
Resistant starch (RS) is any starch or starch digestion products that are not digested and absorbed in the stomach or small intestine and pass on to the large intestine. RS has been categorized into four types:
- RS1 – Physically inaccessible or undigestible resistant starch, such as that found in seeds or legumes and unprocessed whole grains.
- RS2 – Resistant starch is inaccessible to enzymes due to starch conformation, as in green bananas and high amylose corn starch
- RS3 – Resistant starch that is formed when starch-containing foods are cooked and cooled, such as pasta. Occurs due to retrogradation, which refers to the collective processes of dissolved starch becoming less soluble after being heated and dissolved in water and then cooled.
- RS4 – Starches that have been chemically modified to resist digestion
Processing may affect the natural resistant starch content of foods. In general, processes that break down structural barriers to digestion reduce resistant starch content, with greater reductions resulting from processing. Whole grain wheat may contain as high as 14% resistant starch, while milled wheat flour may contain only 2%. Resistant starch content of cooked rice may decrease due to grinding or cooking.
Other types of processing increase resistant starch content. If cooking includes excess water, the starch is gelatinized and becomes more digestible. However, if these starch gels are then cooled, they can form starch crystals resistant to digestive enzymes (Type RS3 or retrograded resistant starch), such as those occurring in cooked and cooled cereals or potatoes (e.g., potato salad). Cooling a boiled potato overnight increases the amount of resistant starch.
Resistant starch is considered both a dietary fiber and a functional fiber, depending on whether it is naturally in foods or added. Although the U.S. Institute of Medicine has defined total fiber as equal to functional fiber plus dietary fiber, U.S. food labeling does not distinguish between them.
|Examples of naturally occurring resistant starch|
(1 cup is ≈227 grams)
|grams per 100 grams (%)|
|Banana flour, from green bananas||1 cup, uncooked||42–52.8||~20.9 (dry)|
|Banana, raw, slightly green||1 medium, peeled||4.7|
|High amylose RS2 corn resistant starch||1 tablespoon (9.5 g)||4.5||47.4 (dry)|
|Oats, rolled||1 cup, uncooked (81.08 g)||17.6||21.7 (dry)|
|Green peas, frozen||1 cup, cooked (160 g)||4.0||2.5|
|White beans||1 cup, cooked (179 g)||7.4||4.1|
|Lentils||1 cup cooked (198 g)||5.0||2.5|
|Cold pasta||1 cup (160g)||1.9||1.2|
|Pearl barley||1 cup cooked (157 g)||3.2||2.03|
|Cold potato||1/2" diameter||0.6 – 0.8|
|Oatmeal||1 cup cooked (234 g)||0.5||0.2|
The Institute of Medicine Panel on the Definition of Dietary Fiber proposed two definitions: functional fiber as "isolated, nondigestible carbohydrates that have beneficial physiological effects in humans", and dietary fiber as "nondigestible carbohydrates and lignin that are intrinsic and intact in plants." They also proposed that the prior classifications of soluble versus insoluble be phased out and replaced with viscous versus fermentable for each specific fiber.
Starch has been consumed by people and animals for thousands of years. Thus, foods containing resistant starch are already commonly consumed.
It has been estimated that average resistant starch intake in developed countries ranges from 3–6 grams/day for Northern Europeans, Australians and Americans, 8.5 grams/day for Italians and 10–15 grams/day in Indian and Chinese diets. The higher consumption of starch-containing foods like pasta and rice likely accounts for higher intake of resistant starch in Italy, India and China.
Several studies have found that the traditional African diet is high in resistant starch. Rural black South Africans consume an average of 38 grams of resistant starch per day by having cooked and cooled corn porridge and beans in their diets.
Isolated and extracted resistant starch and foods rich in resistant starch have been used to fortify foods to increase their dietary fiber content. Typically, food fortification utilizes RS2 resistant starch from high amylose corn, RS3 resistant starch from cassava and RS4 resistant starch from wheat and potato, as these sources can survive varying degrees of food processing without losing their resistant starch content.
Resistant starch has a small particle size, white appearance, bland flavor and low water-holding capacity. Resistant starch typically replaces flour in foods such as bread and other baked goods, pasta, cereal and batters because it can produce foods with similar color and texture of the original food. It has also been used for its textural properties in imitation cheese.
Some types of resistant starch are used as dietary supplements in the United States. RS2 from potato starch and green banana starch maintain their resistance as long as they are consumed raw and unheated. If they are heated or baked, these types of starch may become rapidly digestible. RS2 resistant starch from high amylose corn can be consumed raw or baked into foods.
- Asp NG. (1992). "Resistant starch. Proceedings from the second plenary meeting of EURESTA: European FLAIR Concerted Action No. 11 on physiological implications of the consumption of resistant starch in man. Crete, 29 May-2 June 1991". European Journal of Clinical Nutrition. 46 (Suppl 2): S1–148. PMID 1425538.
- Topping, D. L.; Fukushima, M.; Bird, A. R. (2003). "Resistant starch as a prebiotic and synbiotic: state of the art". Proceedings of the Nutrition Society. 62 (1): 171–176. doi:10.1079/PNS2002224. PMID 12749342.
- National Academy of Sciences. Institute of Medicine. Food and Nutrition Board. (2005). Chapter 7 Dietary, Functional, and Total Fiber in Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein and Amino Acids. Washington DC, USA: National Academies Press. pp. 339–421. ISBN 978-0-309-08525-0.
- Brouns, Fred; Kettitz, Bernd; Arrigoni, Eva (2002). "Resistant starch and "the butyrate revolution"". Trends in Food Science & Technology. 13 (8): 251–261. doi:10.1016/S0924-2244(02)00131-0.
- Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
- Grabitke, Hollie A.; Slavin, Joanne L. (2009). "Gastrointestinal Effects of Low-Digestible Carbohydrates". Critical Reviews in Food Science and Nutrition. 49 (4): 327–360. doi:10.1080/10408390802067126. PMID 19234944. S2CID 205689161.
- Birkett, A. M.; Brown, I. L. (2007). Chapter 4: Resistant Starch and Health in Technology of Functional Cereal Products. Boca Raton, Florida, USA: Woodhead Publishing Limited. pp. 63–85. ISBN 978-1-84569-177-6.
- Sajilata, M. G.; Singhal, Rekha S.; Kulkarni, Pushpa R. (January 2006). "Resistant Starch – A Review". Comprehensive Reviews in Food Science and Food Safety. 5 (1): 1–17. doi:10.1111/j.1541-4337.2006.tb00076.x.
- Englyst, H. N.; Kingman, S. M.; Cummings, J. H. (October 1992). "Classification and Measurement of Nutritionally Important Starch Fractions". European Journal of Clinical Nutrition. 46 (Suppl 2): S33–50. PMID 1330528.
- Sharma, Alka; Yadav, Baljeet Singh; Ritika (2008). "Resistant Starch: Physiological Roles and Food Applications". Food Reviews International. 24 (2): 193–234. doi:10.1080/87559120801926237.
- Asp, N.-G.; van Amelsvoort, J. M. M.; Hautvast, J. G. A. J. (1996). "Nutritional Implications of Resistant Starch". Nutrition Research Reviews. 9 (1): 1–31. doi:10.1079/NRR19960004. PMID 19094263.
- Bird, A.; Conlon, M.; Christophersen, C.; Topping, D. (2010). "Resistant starch, large bowel fermentation and a broader perspective of prebiotics and probiotics". Beneficial Microbes. 1 (4): 423–431. doi:10.3920/BM2010.0041. PMID 21831780.
- Pryde, Susan E.; Duncan, Sylvia H.; Hold, Georgina L.; Stewart, Colin S.; Flint, Harry J. (2002). "The microbiology of butyrate formation in the human colon" (PDF). FEMS Microbiology Letters. 217 (2): 133–139. doi:10.1111/j.1574-6968.2002.tb11467.x. PMID 12480096.
- Andoh, Akira; Tsujikawa, Tomoyuki; Fujiyama, Yoshihide (2003). "Role of Dietary Fiber and Short-Chain Fatty Acids in the Colon". Current Pharmaceutical Design. 9 (4): 347–358. doi:10.2174/1381612033391973. PMID 12570825.
- Cummings, John H.; Macfarlane, George T.; Englyst, Hans N. (2001). "Prebiotic digestion and fermentation". Am J Clin Nutr. 73 (suppl): 415S–420S. doi:10.1093/ajcn/73.2.415s. PMID 11157351.
- Grabitske, HA; Slavin, JL (2009). "Gastrointestinal effects of low-digestible carbohydrates". Critical Reviews in Food Science and Nutrition. 49 (4): 327–360. doi:10.1080/10408390802067126. PMID 19234944. S2CID 205689161.
- "Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids". Institute of Medicine, US National Academy of Sciences. 2013. Retrieved 30 July 2015.
- Ashwar, Bilal Ahmad; Gani, Adil; Shah, Asima; Wani, Idrees Ahmed; Masoodi, Farooq Ahmad (2015). "Preparation, health benefits and applications of resistant starch – a review". Starch – Stärke. 68 (Epub 4 June 2015): 287–301. doi:10.1002/star.201500064.
- Lockyer, S.; Nugent, A.P. (2017). "Health effects of resistant starch". Nutrition Bulletin. 42: 10–41. doi:10.1111/nbu.12244.
- Wang, Yong; Chen, Jing; Song, Ying-Han; Zhao, Rui; Xia, Lin; Chen, Yi; Cui, Ya-Ping; Rao, Zhi-Yong; Zhou, Yong; Zhuang, Wen; Wu, Xiao-Ting (5 June 2019). "Effects of the resistant starch on glucose, insulion, insulin resistance, and lipid parameters in overweight or obese adults: a systemic review and meta-analysis". Nutrition & Diabetes. 9 (1): 19. doi:10.1038/s41387-019-0086-9. PMC 6551340. PMID 31168050.
due to potential confounding, individual variations and gut microbiota composition, this result should be carefully considered and be confirmed by further study
- Meenu, Maninder; Xu, Baojun (9 July 2018). "A critical review on anti-diabetic and anti-obesity effects of dietary resistant starch". Critical Reviews in Food Science and Nutrition. 59 (18): 3019–3031. doi:10.1080/10408398.2018.1481360. PMID 29846089. S2CID 44110136.
- Balentine, Douglas (13 December 2016). "Letter announcing decision for a health claim for high-amylose maize starch (containing type-2 resistant starch) and reduced risk of type 2 diabetes mellitus (Docket Number FDA-2015-Q-2352)". www.regulations.gov. U.S. Food and Drug Administration. Retrieved 16 December 2016.
there is limited credible scientific evidence for a qualified health claim for high-amylose maize resistant starch and reduced risk of type 2 diabetes
- "FDA Approve Claim That High-Amylose Maize Resistant Starch Reduces Type 2 Diabetes Risk". Food Ingredients, CNS Media BV, Arnhem, The Netherlands. 19 December 2016. Retrieved 9 January 2017.
- Vahdat, M.; Hosseini, S.A.; Khalatbari Mohseni, G.; Heshmati, J.; Rahimlou, M. (15 April 2020). "Effects of resistant starch interventions on circulating inflammatory biomarkers: a systematic review and meta-analysis of randomized controlled trials". Nutrition Journal. 19 (1): Article 33. doi:10.1186/s12937-020-00548-6. PMC 7158011. PMID 32293469.
- AACC (1999). "CHAPTER 1: Starch Structure". Starch Structure in "Starches". St. Paul, Minnesota, USA: American Association of Cereal Chemists. pp. 1–11. doi:10.1094/1891127012.001. ISBN 978-1-891127-01-4.
- Svihus, B.; Uhlen, A.K.; Marstad, O.M. (2005). "Effect of starch granule structure, associated components and processing on nutritive value of cereal starch: a review". Animal Feed Science and Technology. 122 (3–4): 303–320. doi:10.1016/j.anifeedsci.2005.02.025.
- Taggart, Pauline (2004). "12". In Eliasson, Ann-Charlotte (ed.). Starch as an ingredient: manufacture and applications. Starch in food, Structure, function and applications. Boca Raton FL: CRC Press. p. 380. ISBN 1-85573-731-0.
- Wang, Shujun; Copeland, Les (1 November 2013). "Molecular disassembly of starch granules during gelatinization and its effect on starch digestibility: a review". Food & Function. 4 (11): 1564–80. doi:10.1039/C3FO60258C. PMID 24096569.
- Wang, Shujun; Li, Caili; Copeland, Les; Niu, Qing; Wang, Shuo (2015). "Starch retrogradation: a comprehensive review". Comprehensive Reviews in Food Science and Food Safety. 14 (5): 568–585. doi:10.1111/1541-4337.12143.
- Zaman, Siti A.; Sarbini, Shahrui R. (2015). "The Potential of Resistant Starch as a Prebiotic" (PDF). Critical Reviews in Biotechnology. 36 (3): 578–84. doi:10.3109/07388551.2014.993590. PMID 25582732. S2CID 25974073.
- Berry, C. S. (1986). "Resistant starch: Formation and measurement of starch that survives exhaustive digestion with amylolytic enzymes during the determination of dietary fibre". Journal of Cereal Science. 4 (4): 301–314. doi:10.1016/S0733-5210(86)80034-0.
- Finocchiaro, E. Terry; Birkett, Anne; Okoniewska, Monika (2009). 10 – Resistant Starch in Fiber Ingredients: Food Applications and Health Benefits. CRC Press. pp. 205–248. ISBN 978-1420043853.
- Bednar, G. E.; Patil, A. R.; Murray, S. M.; Grieshoop, C. M.; Merchen, N. R.; Fahey, G. C. (2001). "Starch and Fiber Fractions in Selected Food and Feed Ingredients Affect Their Small Intestinal Digestibility and Fermentability and Their Large Bowel Fermentability In Vitro in a Canine Model". The Journal of Nutrition. 131 (2): 276–286. doi:10.1093/jn/131.2.276. PMID 11160546.
- Fuentes-Zaragoza, E.; Riquelme-Navarrete, M. J.; Sánchez-Zapata, E.; Pérez-Álvarez, J. A. (2010). "Resistant starch as functional ingredient: A review". Food Research International. 43 (4): 931–942. doi:10.1016/j.foodres.2010.02.004.
- Sáyago-Ayerdi, S. G.; Tovar, J.; Osorio-Díaz, P.; Paredes-López, O.; Bello-Pérez, L. A. (2005). "In Vitro Starch Digestibility and Predicted Glycemic Index of Corn Tortilla, Black Beans, and Tortilla−Bean Mixture: Effect of Cold Storage". Journal of Agricultural and Food Chemistry. 53 (4): 1281–1285. doi:10.1021/jf048652k. PMID 15713053.
- Muir, J. G.; O'Dea, K. (1992). "Measurement of resistant starch: factors affecting the amount of starch escaping digestion in vitro". The American Journal of Clinical Nutrition. 56 (1): 123–7. doi:10.1093/ajcn/56.1.123. PMID 1609748.
- Jo Ann Tatum Hattner; Susan Anderes (2009). Gut Insight: probiotics and prebiotics for digestive health and well-being. p. 45. ISBN 978-0-615-28524-5. Retrieved 16 March 2011.
- Lloyd W. Rooney; Lusas, Edmund W. (2001). Snack Foods Processing. Boca Raton: CRC. p. 134. ISBN 978-1-56676-932-7. Retrieved 16 March 2011.
- National Research Council (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. National Academies Press. doi:10.17226/10490. ISBN 978-0309085373.
- Jane Higdon (2007). An evidence-based approach to dietary phytochemicals. New York: Thieme Medical Publishers. p. 102. ISBN 978-3-13-141841-8. Retrieved 16 March 2011.
- Bier, Dennis M.; Alpers, David H.; Stenson, William F.; Taylor, Beth Weir (2008). Manual of nutritional therapeutics. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 419. ISBN 978-0-7817-6841-2. Retrieved 16 March 2011.
- Murphy M, Douglass JS, Birkett A. Resistant starch intake in the United States, Journal of the American Dietetic Association 2008; 108:67–78.
- Moongngarm; et al. (2014). "Resistant Starch and Bioactive Contents of Unripe Banana Flour as Influenced by Harvesting Periods and ITS Application". American Journal of Agricultural and Biological Sciences. 9 (3): 457–465. doi:10.3844/ajabssp.2014.457.465.
- "Federal Register | Food Labeling: Revision of Reference Values and Mandatory Nutrients". 2 November 2007. Retrieved 18 March 2011.
- Baghurst, P. A.; Baghurst, K. I.; Record, S. J. (1996). "Dietary Fibre, Non-starch Polysaccharides and Resistant Starch – A Review". Food Australia. 48 (3): Supplement S1–S35.
- Murphy, M. M.; Douglass, J. S.; Birkett, A. (2008). "Resistant starch intakes in the United States". J Am Diet Assoc. 108 (1): 67–78. doi:10.1016/j.jada.2007.10.012. PMID 18155991.
- Baghurst, Katrine I.; Baghurst, Peter A.; Record, Sally J. (2000). Chapter 7.3 Dietary Fiber, Nonstarch Polysaccharide, and Resistant Starch Intakes in Australia in CRC Handbook of Dietary Fiber in Human Nutrition (3 ed.). Boca Raton, Florida: CRC Press LLC. pp. 583–591. ISBN 978-0-8493-2387-4.
- Brighenti, Furio; Casiraghi, M. Cristina; Baggio, Cristina (1998). "Resistant Starch in the Italian Diet". British Journal of Nutrition. 80 (4): 333–341. doi:10.1017/S0007114598001391. PMID 9924275.
- Chen, Liyong; Liu, Ruiping; Qin, Chengyong; Meng, Yan; Zhang, Jie; Wang, Yun; Xu, Guifa (2010). "Sources and Intake of Resistant Starch in the Chinese Diet". Asia Pac J Clin Nutr. 19 (2): 274–282. PMID 20460244.
- O'Keefe, Stephen J. D.; Li, Jia V.; et al. (2015). "Fat, fibre and cancer risk in African Americans and rural Africans". Nature Communications. 6 (Article number 6342): 6342. Bibcode:2015NatCo...6.6342O. doi:10.1038/ncomms7342. PMC 4415091. PMID 25919227.
- Sayago-Ayerdi, S. G.; Torvar, J.; Blancas-Benitez, F. J.; Bello-Perez, L. A. (2011). "Resistant starch in common starchy foods as an alternative to increase dietary fibre intake". Journal of Food and Nutrition Research. 50 (1): 1–12.
- Raigond, P.; Ezekiel, R.; Raigond, B. (2014). "Resistant Starch in Food: A Review". Journal of the Science of Food and Agriculture. Epub 21 Oct 2014 (10): 1968–1978. doi:10.1002/jsfa.6966. PMID 25331334.
- Homayouni, Aziz; Amini, Amir; Keshtiban, Ata Khodavirdivand; Mortazavian, Amir Mohammad; Esazadeh, Karim; Pourmoradian, Samira (2014). "Resistant starch in food industry: A changing outlook for consumer and producer". Starch – Stärke. 66 (1–2): 102–114. doi:10.1002/star.201300110.
- Evans, I. D.; Haisman, D. R. (1982). "The Effect of Solutes on the Gelatinization Temperature Range of Potato Starch". Starch -Stärke. 34 (7): 224–231. doi:10.1002/star.19820340704.
- Birt, Diane F.; Boylston, Terri; et al. (2013). "Resistant Starch: Promise for Improving Human Health" (PDF). Advances in Nutrition. 4 (6): 587–601. doi:10.3945/an.113.004325. PMC 3823506. PMID 24228189.