Resistant starch
Resistant starch (RS) is starch, including its degradation products, that escapes from digestion in the small intestine of healthy individuals.[1][2] Resistant starch occurs naturally in foods, but it can also be added as part of dried raw foods, or used as an additive in manufactured foods.[3]
Some types of resistant starch (RS1, RS2 and RS3) are
Resistant starch has similar
Origin and history
The concept of resistant starch arose from research in the 1970s
The European Commission-supported-research eventually led to a definition of resistant starch.[8][12]
Health effects
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).[11] 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.[11][13]
The fermentation of resistant starch produces
Studies have shown that resistant starch supplementation was well tolerated.[17] 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,[18] an amount exceeding the total recommended intake for dietary fiber of 25–38 grams per day.[19] When isolated resistant starch is used to substitute for flour in foods, the glycemic response of that food is reduced.[20][21]
There is limited evidence that resistant starch can improve fasting glucose, fasting insulin, insulin resistance and sensitivity, especially in individuals who are diabetic, overweight or obese.[22][23][24][25][26] 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."[27][28]
Resistant starch may reduce appetite, especially with doses of 25 grams or more.[29]
Resistant starch may reduce
There is limited evidence that resistant starch might improve
Starch structure
Plants store starch in tightly packed granules, consisting of layers of amylose and amylopectin.[36] 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.[37]
Starch granule characteristics[38] 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 Tapioca 4-35 Oval, Truncated 62-73 Potato 5-100 Oval, Spherical 59-68 Wheat 1-45 Round, Lenticular 58-64 Rice 3-8 Polygonal, Spherical
Compound granules68-78 High amylose maize 5-30 Polygonal, Irregular
Elongated63-92 (not gelatinized in boiling water)
Raw starch granules resist digestion, e.g., 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.[39] 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.[40]
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.[41]
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.[42]
Definition and categorization
This section is missing information about which chemical modifications resist digestion: phosphate crosslink, "acid dextrinization" (and yes, resistant dextrin should be created to redirect on here). (December 2023) |
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 five types:[9]
- RS1 – Physically inaccessible or undigestible resistant starch, such as that found in seeds or legumes and unprocessed whole grains. This starch is bound within the fibrous cell walls of the aforementioned foods.
- RS2 – Resistant starch is inaccessible to enzymes due to starch conformation, as in green bananas, raw potatoes, and high amylose corn starch.
- RS3 – Resistant starch that is formed when starch-containing foods (e.g. rice, potatoes, pasta) are cooked and cooled. 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.
- RS5 – Starches that are complexed with lipids.[43][44]
Processing effects
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.[45] Whole grain wheat may contain as high as 14% resistant starch, while milled wheat flour may contain only 2%.[46] Resistant starch content of cooked rice was found to decrease due to grinding; resistant starch content of oats dropped from 16 to 3% during cooking.[20]
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),[9] as in cooked and cooled cereals and potatoes (e.g., potato salad).[47][48] Cooling boiled potatoes overnight at 4 °C (39 °F) was found to increase the amount of resistant starch by a factor of 2.8.[49]
High amylose varieties of corn, wheat, barley, potato and rice have been naturally bred to increase the resistant starch content that will survive baking and mild extrusion processing, which enables the delivery of resistant starch in processed foods.[50]
Nutritional information
Resistant starch is considered both a dietary fiber and a functional fiber, depending on whether it is naturally in foods or added.
Examples of naturally occurring resistant starch[56] Food Serving size
(1 cup is ≈227 grams)Resistant starch
(grams)grams per 100 grams (%) Banana flour,[57] 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) High amylose RS2 wheat resistant starch 1/4 cup (30 g) 5.0 16.7 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.[58]
Uses
In food
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][47][59][60][61] 8.5 grams/day for Italians[62] and 10–15 grams/day in Indian and Chinese diets.[8][63] 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.[13] 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.[64]
RS2 resistant starch from high amylose wheat and high amylose corn can be baked into foods, usually replacing flour or other high glycemic carbohydrates.[65][66]
Isolated
Isolated and extracted resistant starch and foods rich in resistant starch have been used to fortify foods to increase their dietary fiber content.[47][59][67] Typically, food fortification utilizes RS2 resistant starch from high amylose corn or high amylose wheat, 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.[9]
Resistant starch has a small particle size, white appearance, bland flavor and low water-holding capacity.[9] 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.[68] It has also been used for its textural properties in imitation cheese.[69]
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.[70]
References
- PMID 1425538.
- PMID 12749342.
- ISBN 978-0-309-08525-0.
- .
- ISSN 0190-8286. Retrieved 13 June 2023.
- ^ Elsevier, Dorland's Illustrated Medical Dictionary, Elsevier.
- S2CID 205689161.
- ^ ISBN 978-1-84569-177-6.
- ^ PMID 33412740.
- PMID 1330528.
- ^ .
- PMID 19094263.
- ^ PMID 21831780.
- PMID 12480096.
- PMID 12570825.
- PMID 11157351.
- PMID 34871343.
- S2CID 205689161.
- ISBN 9780309085250. Retrieved 30 July 2015.
- ^ .
- .
- S2CID 216082637.
- S2CID 225468482.
- S2CID 221844639.
- PMID 31168050.
due to potential confounding, individual variations and gut microbiota composition, this result should be carefully considered and be confirmed by further study
- 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.
- S2CID 231703336. Retrieved 20 February 2022.
- S2CID 49303895.
- PMID 32293469.
- PMID 35096939.
- PMID 33437217. Retrieved 20 February 2022.
- PMID 34967190. Retrieved 20 February 2022.
- S2CID 247010531.
- ISBN 978-1-891127-01-4.
- .
- ISBN 1-85573-731-0.
- PMID 24096569.
- S2CID 82219048.
- S2CID 25974073.
- .
- S2CID 219498577.
- S2CID 233839696.
- ISBN 978-1420043853.
- PMID 11160546.
- ^ .
- PMID 15713053.
- PMID 1609748.
- S2CID 91869134.
- ISBN 978-0-615-28524-5. Retrieved 16 March 2011.
- ISBN 978-1-56676-932-7. Retrieved 16 March 2011.
- ISBN 978-0309085373.
- ISBN 978-3-13-141841-8. Retrieved 16 March 2011.
- 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.
- .
- ^ "Federal Register | Food Labeling: Revision of Reference Values and Mandatory Nutrients". 2 November 2007. Retrieved 18 March 2011.
- ^ a b 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.
- PMID 18155991.
- ISBN 978-0-8493-2387-4.
- PMID 9924275.
- PMID 20460244.
- PMID 25919227.
- PMID 24228189.
- PMID 35102419.
- ^ 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.
- PMID 25331334.
- .
- .