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 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. [4] [5]
Resistant starch has similar physiological effects as dietary fiber, [6] behaving as a mild laxative and possibly causing flatulence. [7]
The concept of resistant starch arose from research in the 1970s [8] and is currently considered to be one of three starch types: rapidly digested starch, slowly digested starch and resistant starch, [9] [10] each of which may affect levels of blood glucose. [11]
The European Commission-supported-research eventually led to a definition of resistant starch. [8] [12]
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 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. [14] [15] The fermentation of resistant starch produces more butyrate than other types of dietary fibers. [16]
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 low-density cholesterol. [30]
There is limited evidence that resistant starch might improve inflammatory biomarkers, including interleukin-6, tumor necrosis factor alpha, and C-reactive protein. [31] [32] [33] [34] [35]
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 granules | 68-78 |
High amylose maize | 5-30 | Polygonal, Irregular Elongated | 63-92 (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]
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]
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]
Resistant starch is considered both a dietary fiber and a functional fiber, depending on whether it is naturally in foods or added. [51] [52] [53] Although the U.S. Institute of Medicine has defined total fiber as equal to functional fiber plus dietary fiber, [54] U.S. food labeling does not distinguish between them. [55]
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]
The 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 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 to 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]
A carbohydrate is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 and thus with the empirical formula Cm(H2O)n, which does not mean the H has covalent bonds with O. However, not all carbohydrates conform to this precise stoichiometric definition, nor are all chemicals that do conform to this definition automatically classified as carbohydrates.
Polysaccharides, or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with water (hydrolysis) using amylase enzymes as catalyst, which produces constituent sugars. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch, glycogen and galactogen and structural polysaccharides such as hemicellulose and chitin.
Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets, and is contained in large amounts in staple foods such as wheat, potatoes, maize (corn), rice, and cassava (manioc).
Dietary fiber or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzymes. Dietary fibers are diverse in chemical composition and can be grouped generally by their solubility, viscosity and fermentability which affect how fibers are processed in the body. Dietary fiber has two main subtypes: soluble fiber and insoluble fiber which are components of plant-based foods such as legumes, whole grains, cereals, vegetables, fruits, and nuts or seeds. A diet high in regular fiber consumption is generally associated with supporting health and lowering the risk of several diseases. Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulins, lignins, chitins, pectins, beta-glucans, and oligosaccharides.
Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life and good health. Poor nutrition is a chronic problem often linked to poverty, food security, or a poor understanding of nutritional requirements. Malnutrition and its consequences are large contributors to deaths, physical deformities, and disabilities worldwide. Good nutrition is necessary for children to grow physically and mentally, and for normal human biological development.
The glycemic (glycaemic) index is a number from 0 to 100 assigned to a food, with pure glucose arbitrarily given the value of 100, which represents the relative rise in the blood glucose level two hours after consuming that food. The GI of a specific food depends primarily on the quantity and type of carbohydrate it contains, but is also affected by the amount of entrapment of the carbohydrate molecules within the food, the fat and protein content of the food, the amount of organic acids in the food, and whether it is cooked and, if so, how it is cooked. GI tables, which list many types of foods and their GIs, are available. A food is considered to have a low GI if it is 55 or less; high GI if 70 or more; and mid-range GI if 56 to 69.
Low-carbohydrate diets restrict carbohydrate consumption relative to the average diet. Foods high in carbohydrates are limited, and replaced with foods containing a higher percentage of fat and protein, as well as low carbohydrate foods.
Inulins are a group of naturally occurring polysaccharides produced by many types of plants, industrially most often extracted from chicory. The inulins belong to a class of dietary fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes. Most plants that synthesize and store inulin do not store other forms of carbohydrate such as starch. In 2018, the United States Food and Drug Administration approved inulin as a dietary fiber ingredient used to improve the nutritional value of manufactured food products. Using inulin to measure kidney function is the "gold standard" for comparison with other means of estimating glomerular filtration rate.
Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch, making up approximately 20–30%. Because of its tightly packed helical structure, amylose is more resistant to digestion than other starch molecules and is therefore an important form of resistant starch.
Amylopectin is a water-insoluble polysaccharide and highly branched polymer of α-glucose units found in plants. It is one of the two components of starch, the other being amylose.
Maltodextrin is a name shared by two different families of chemicals. Both families are glucose polymers, but have little chemical or nutritional similarity.
Prebiotics are compounds in food that foster growth or activity of beneficial microorganisms such as bacteria and fungi. The most common environment concerning their effects on human health is the gastrointestinal tract, where prebiotics can alter the composition of organisms in the gut microbiome.
Alpha-glucosidase inhibitors (AGIs) are oral anti-diabetic drugs used for diabetes mellitus type 2 that work by preventing the digestion of carbohydrates. They are found in raw plants/herbs such as cinnamon and bacteria. Carbohydrates are normally converted into simple sugars (monosaccharides) by alpha-glucosidase enzymes present on cells lining the intestine, enabling monosaccharides to be absorbed through the intestine. Hence, alpha-glucosidase inhibitors reduce the impact of dietary carbohydrates on blood sugar.
A diabetic diet is a diet that is used by people with diabetes mellitus or high blood sugar to minimize symptoms and dangerous complications of long-term elevations in blood sugar.
Refined grains have been significantly modified from their natural composition, in contrast to whole grains. The modification process generally involves the mechanical removal of bran and germ, either through grinding or selective sifting.
The Western pattern diet is a modern dietary pattern that is generally characterized by high intakes of pre-packaged foods, refined grains, red meat, processed meat, high-sugar drinks, candy and sweets, fried foods, industrially produced animal products, butter and other high-fat dairy products, eggs, potatoes, corn, and low intakes of fruits, vegetables, whole grains, pasture-raised animal products, fish, nuts, and seeds.
Weight management refers to behaviors, techniques, and physiological processes that contribute to a person's ability to attain and maintain a healthy weight. Most weight management techniques encompass long-term lifestyle strategies that promote healthy eating and daily physical activity. Moreover, weight management involves developing meaningful ways to track weight over time and to identify the ideal body weights for different individuals.
Pea protein is a food product and protein supplement derived and extracted from yellow and green split peas, Pisum sativum. It can be used as a dietary supplement to increase an individual's protein or other nutrient intake, or as a substitute for other food products. As a powder, it is used as an ingredient in food manufacturing, such as a thickener, foaming agent, or an emulsifier.
Banana flour is a powder traditionally made of green bananas. Historically, banana flour has been used in Africa and Jamaica as a cheaper alternative to wheat flour. It is now often used as a gluten-free replacement for wheat flours or as a source of resistant starch, which has been promoted by certain dieting trends such as paleo and primal diets and by some recent nutritional research. Banana flour, due to the use of green bananas, has a very mild banana flavor raw, and when cooked, it has an earthy, nonbanana flavor; it also has a texture reminiscent of lighter wheat flours and requires about 25% less volume, making it a good replacement for white and white whole-wheat flour.
Oat β-glucans are water-soluble β-glucans derived from the endosperm of oat kernels known for their dietary contribution as components of soluble fiber. Due to their property to lower serum total cholesterol and low-density lipoprotein cholesterol, and potentially reduce the risk of cardiovascular diseases, oat β-glucans have been assigned a qualified health claim by the European Food Safety Authority and the US Food and Drug Administration.
due to potential confounding, individual variations and gut microbiota composition, this result should be carefully considered and be confirmed by further study
there is limited credible scientific evidence for a qualified health claim for high-amylose maize resistant starch and reduced risk of type 2 diabetes