IngredientsAmylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. Together with amylopectin, it is one of the two components of starch, making up approximately 20–25% of it. Its IUPAC name as a class of compound is (1→4)-α-D-glucan, and it is registered under CAS number 9005-82-7. The compound is classified as a homopolysaccharide, meaning it is composed exclusively of a single monosaccharide monomer (D-glucose).
Amylose is typically the second most abundant component of starch, accounting for 20–30% of its weight, and is generally recognized as a linear or slightly branched molecule with a degree of polymerization (DP) ranging from approximately 1000 to 5000, depending on the source of the starch. Amylose varies in molecular weight across different starch sources, ranging from 1.3 × 105 to 5 × 105, with some molecules exhibiting slight branching through 5–20 chains.
Experimental evidence indicates that amylose is not a straight chain of glucose units but instead is coiled like a spring, with six glucose monomers per turn. It can exist in a disordered amorphous conformation, found both in starch granules and in hydrated amylose (when starch is cooked in water). There are also two different helical forms: starting with purified amylose, it can bind with another amylose molecule in a double helix (A or B form), or it can bind with a guest molecule such as iodine, a fatty acid, or an aromatic compound, known as the V form.
Amylose can also form single-helical complexes with many chemicals (complexing agents) that consist of a hydrophobic moiety, such as alcohols and fatty acids. The amylose single-helical complex, also known as an inclusion complex, has the hydrophobic moiety of the complexing agent located inside the hydrophobic cavity of the helix. When coiled in this fashion, amylose has just enough room in its core to accommodate an iodine molecule. The characteristic blue-violet color that appears when starch is treated with iodine is due to the formation of the amylose-iodine complex.
Starch is the most important source of carbohydrates in the human diet and accounts for more than 50% of carbohydrate intake. It occurs in plants in the form of granules, and these are particularly abundant in seeds (especially the cereal grains) and tubers, where they serve as a storage form of carbohydrates.
Starch is synthesized in green plants as a mixture of two polymers — amylose (≈25%) and amylopectin (≈75%) — in different amounts and with different characteristics, depending on the botanic origin. The major dietary sources include maize (corn), wheat, rice, potato, barley, legumes, and cassava. Amylose content varies substantially by species and cultivar. Standard maize starch contains roughly 25–28% amylose, while conventional waxy maize contains less than 1% amylose. High-amylose maize cultivars, developed through selective breeding and genetic modification, can contain 50–70% or more amylose. High amylose maize starch (HAMS) is a resistant corn starch type 2 (RS2) derived from high amylose maize starch and containing approximately 70% amylose.
Starch is biosynthesized as semicrystalline granules with varying polymorphic types and degrees of crystallinity. The diameters of the microscopic granules in starch range from 2 to 100 μm, and the crystallinity is 15–45%. When water is heated, starch becomes soluble. The granules swell and burst, the semicrystalline structure is lost, and the smaller amylose molecules start leaching out of the granule, forming a network that holds water and increasing the mixture's viscosity. This process is called starch gelatinization.
Amylose is encountered both as a naturally occurring constituent of starchy foods and as a purified or enriched ingredient in commercial preparations. Key forms include:
Amylose, as a distinct molecular entity, was not characterised until the twentieth century. Its identification as the linear fraction of starch is generally attributed to work in the 1940s, particularly studies employing iodine-binding and fractionation techniques. As a specific named compound, it therefore has no independent pre-modern history of use. Its nutritional and functional history is inseparable from the history of starch-rich foods consumed by virtually every human agricultural civilisation.
Starch-containing foods — including grains (wheat, rice, maize, barley, millet, sorghum), tubers (potato, cassava, taro, yam), and legumes (lentils, beans) — have formed the dietary foundation of cultures on every inhabited continent for thousands of years. Starch granules are particularly abundant in seeds (especially cereal grains) and tubers, where they serve as a storage form of carbohydrates. The breakdown of starch to glucose nourishes the plant during periods of reduced photosynthetic activity.
In the context of traditional food processing, cooking methods that affect starch digestibility — and therefore the proportion of amylose that reaches the colon intact — have been practiced unknowingly for millennia. Processes such as cooking and then cooling rice or legumes, fermentation of grain porridges (e.g., ogi in West Africa, fermented rice preparations in East and Southeast Asia), and sun-drying of cooked starchy foods increase retrograded amylose (RS3) content, functionally enriching these foods with resistant starch. The potential of tropical starchy plants such as plantain (Musa paradisiaca), breadfruit (Artocarpus communis), and sweet potato (Ipomoea batatas) for the development of fermented foods was investigated by exploiting the capacity of some lactic acid bacteria to hydrolyze starch. These traditional practices produced foods with modified starch digestibility, though the molecular basis in amylose retrogradation was not understood at the time.
The deliberate cultivation of high-amylose crop varieties is a relatively modern development, arising from plant genetics research in the mid-twentieth century. The identification of the amylose extender (ae) mutation in maize, and later analogous mutations in barley, wheat, and rice, allowed plant breeders to produce staple crops with substantially elevated amylose content. Dietary supplementation with purified or enriched amylose / high-amylose starch preparations is an exclusively modern practice originating in the late twentieth and early twenty-first centuries.
Amylose itself is the primary bioactive component in high-amylose starch preparations. Its physiological actions are largely downstream consequences of its physical resistance to digestion by human small-intestinal enzymes. High-amylose starch is generally resistant to enzymatic digestion in the gastrointestinal tract, and contains an increased fraction of resistant starch (RS), which is a type of dietary fiber.
Starch is a digestible carbohydrate source that is hydrolyzed by the salivary and pancreatic enzyme, α-amylase. As a result of α-amylase activity, starch is broken down into smaller disaccharides and polysaccharides, which are then acted on by brush border enzymes in the small intestine. Brush border enzymes work to break down disaccharides and polysaccharides into monosaccharides such as glucose, fructose, and galactose, which are then absorbed into the bloodstream.
The linear, tightly packed helical structure of amylose within the starch granule limits access of α-amylase to glycosidic bonds. Amylose-rich starches have been reported to be more durable than amylolysis waxy or typical starches. Specifically, in high-amylose native starches: starch can escape digestion by endogenous enzymes in the small intestine when there is a high concentration of amylose (resistant starch type 2).
Amylose participates in multiple categories of resistant starch: Resistant starch type 2 is resistant to digestion on account of ungelatinized starch molecules tightly packed in the endosperm, making their accessibility to digestive enzymes minimal; resistant starch type 3 is composed of retrograded amylose, which forms a tight, crystalline structure that is inaccessible to digestive enzymes; and resistant starch type 5 comprises a complex of amylose and lipids which can be found naturally in starch granules or can be created through chemical modification.
When amylose reaches the colon intact, it is fermented by the resident microbiota, generating short-chain fatty acids (SCFAs) including acetate, propionate, and butyrate. The prebiotic high amylose maize starch (HAMS) alters the gut microbiome profile and metabolites favorably with an increase in bacteria producing short chain fatty acids (SCFAs) that have significant anti-inflammatory effects.
Butyrate, a short-chain fatty acid, plays a pivotal role in supporting gut health by nourishing colonocytes, promoting barrier function, modulating inflammation, and fostering a balanced microbiome. These fatty acids impact the body by binding to receptors on enteroendocrine cells, influencing hormones like glucagon-like peptide-1 and peptide YY, which regulate appetite and insulin sensitivity.
The gut microbiome can be altered using high-amylose maize starch (HAMS), a well-tolerated source of dietary fiber. Following colonic bacterial fermentation, acetylated and butyrylated HAMS (HAMS-AB) releases large amounts of short chain fatty acids (SCFAs), which are anti-inflammatory and immunomodulatory.
Amylose can form gels through non-covalent cross-linking, facilitated by enzymatic polymerization. This process involves the formation of double helices and inclusion complexes, which contribute to the unique properties of the resulting gels. The distinctive structure of amylose provides many physicochemical features utilized in food technology, medicines, and materials research.
Overview: The most extensively studied clinical application of high-amylose starch preparations is their ability to attenuate postprandial blood glucose and improve insulin sensitivity. Evidence ranges from acute single-meal studies to multi-week randomized controlled trials (RCTs).
Postprandial glycemic response: Substantial evidence indicates that high-amylose maize starch (HM) is associated with blood glucose-lowering effects in animal models and human clinical trials. High-amylose wheat lowers the postprandial glycemic response to bread in healthy adults, as demonstrated in a randomized controlled crossover trial published in the Journal of Nutrition.
In a crossover experimental trial: This study examined the effects of resistant starch known as high-amylose maize starch (HM) as wheat flour substitute in Chinese steamed buns on postprandial glycemic response in healthy human subjects. In a single-blind crossover trial, subjects (female, n=15) consuming 30% HM composite buns had significantly lower postprandial blood glucose response compared with controls within 2 hours after ingestion. HM30 produced a mean incremental area under the curve (iAUC) of 105.2 mmol × min/L compared with the control's mean iAUC of 186.1 mmol × min/L.
Insulin sensitivity (multi-week RCT): One study evaluated the effects of two levels of intake of high-amylose maize type 2 resistant starch (HAM-RS2) on insulin sensitivity in participants with waist circumference ≥89 cm (women) or ≥102 cm (men). Participants received 0 (control starch), 15, or 30 g/d of HAM-RS2 in random order for 4-week periods separated by 3-week washouts. The results indicated that consumption of 15–30 g/d of HAM-RS2 improved insulin sensitivity in overweight and obese men.
The STARCH Trial (prediabetes): In this trial, 68 overweight adults (BMI ≥27 kg/m²) aged 35–75 years with prediabetes were randomized to consume 45 g/d of high-amylose maize (RS2) or an isocaloric amount of the rapidly digestible starch amylopectin (control) for 12 weeks. At baseline and post-intervention, ectopic fat depots were measured by MRI/spectroscopy, energy metabolism by respiratory chamber, and carbohydrate metabolism by HbA1c and intravenous glucose tolerance test. Cardiovascular risk factors — serum lipids, blood pressure, heart rate, and inflammatory markers including hs-CRP, interleukin-6, and TNF-α — were also measured.
Systematic review evidence: Resistant starch types 1 (physically inaccessible) and 2 (high-amylose starch) can significantly lower postprandial glucose in individuals with type 2 diabetes or prediabetes. Dietary interventions using resistant starch may improve glucose metabolism and insulin sensitivity. However, few studies have explored the differential effects of resistant starch type, limiting definitive conclusions about which type or combination is most efficacious.
Evidence strength: Multiple RCTs and at least one systematic review with meta-analysis support an acute postprandial glucose-lowering effect of high-amylose/resistant starch RS2. Effects on longer-term insulin sensitivity in humans are supported by several well-designed RCTs, though results are not entirely uniform and effects may depend on baseline insulin sensitivity, sex, and dose.
Overview: High-amylose starch functions as a prebiotic substrate — it selectively promotes the growth and metabolic activity of beneficial colonic bacteria, particularly those producing butyrate.
High amylose maize starch (HAMS) is a dietary fiber and prebiotic that provides a novel approach to mitigating disease through altering the gut microbiome. Fermentable fiber supplements, high-amylose maize starch, and inulin have shown their ability to enhance SCFA production in the colon.
One clinical trial showed that butyrylated high-amylose maize starch (HAMSB) significantly reduced rectal O6-methyl-guanine adducts and epithelial proliferation induced by high protein diet. Fecal microbial profiles were assessed in three clinical trials, showing that HAMSB supplementation was consistently linked to increased abundance of Parabacteroides distasonis.
Evidence strength: Evidence for prebiotic activity of high-amylose starch in humans is supported by mechanistic plausibility and consistent SCFA data from multiple clinical studies. The specific microbiome changes are considered promising but the evidence base is still growing, with most human studies being small and of short duration.
Overview: Population studies and mechanistic research have generated interest in the potential of amylose-derived butyrate to support colonic epithelial health and potentially reduce colorectal cancer (CRC) risk. Evidence is primarily from animal studies, with early-phase human data.
Increased colonic butyrate from microbial fermentation of fibre may protect from colorectal cancer (CRC). Dietary butyrylated high amylose maize starch (HAMSB) delivers butyrate to the large bowel. The objective of the AusFAP clinical trial was to evaluate potential chemoprotective effects of HAMSB on polyposis in individuals with a genetic form of colon cancer, Familial Adenomatous Polyposis (FAP). The study is a multi-site, double-blind, randomised, placebo-controlled crossover trial undertaken at major hospitals in Australia. After a baseline endoscopy, participants consumed either 40 g/day of HAMSB or placebo (low amylose maize starch) for 26 weeks.
In animal research, large bowel total SCFA, acetate, and butyrate pools and hepatic portal venous plasma SCFA concentrations were higher with greater HAMSB intake. Distal colonic epithelial apoptotic index and colonic mucus thickness increased, while DNA single strand breaks decreased dose-dependently with greater HAMSB intake. These data suggest that increasing large bowel butyrate may reduce the risk of CRC in a dose-dependent manner by enhancing apoptotic surveillance in the colonic epithelium for damaged cells without promoting the risk of tumorigenesis through increased cell proliferation.
The effects of HAMSB in modulating colorectal disturbances and colon health-related biomarkers were reported by three clinical trials and 10 animal studies.
Evidence strength: The mechanistic rationale (butyrate → colonocyte nutrition → apoptotic surveillance → cancer risk reduction) is well supported in vitro and in animals. Human clinical data are limited to a small number of trials focused on biomarker endpoints, with no large-scale primary prevention RCT in the general population having been completed. The link remains biologically plausible but not definitively proven in humans.
Overview: Results from human trials examining the effects of high-amylose starch on lipid profiles are mixed.
Randomized controlled trials report reductions in LDL cholesterol and systemic inflammation with RS supplementation, suggesting benefits that extend to cardiovascular risk reduction and weight management.
In a 12-week crossover RCT: 21 participants (mean age 35 ± 7.0 years; BMI 32.4 ± 3.5 kg/m²) were given 13.5 g Hi-Maize 260 or placebo daily for 4 weeks. Changes in total antioxidant status (p = 0.04) and serum insulin concentrations in 52.4% of participants with insulin levels above 16 µIU/mL at baseline (p = 0.04) were significantly different. The mean serum HDL cholesterol after the intervention was significantly higher than after baseline value (p = 0.04). However, no significant differences were found in serum concentrations of total cholesterol, triacylglycerol, or LDL cholesterol.
In the Maki et al. (2012) study of overweight and obese men using 15–30 g/day of HAM-RS2, there were no significant or clinically meaningful differences in body weight, waist circumference, or blood lipids at the end of each treatment condition.
Evidence strength: Effects on lipids are inconsistent across trials. Some studies observe HDL-raising or LDL-lowering effects; others detect no significant change. Heterogeneity in dose, form of resistant starch, study population, and duration limits firm conclusions. Overall, lipid evidence is considered preliminary and mixed.
The link between RS intake and weight regulation is particularly notable. Clinical data indicate that RS enhances satiety and appetite control, contributing to modest reductions in body weight and fat mass, especially in overweight or diabetic populations.
In a crossover study examining appetite: 14 overweight/obese participants ate a high-fat breakfast and a supplement with native banana starch (NBS), high-amylose maize starch (HMS), or digestible maize starch (DMS) on three separate occasions, with all supplements matched by available carbohydrate content and RS quantity in NBS and HMS identical. Postprandial glycemia, triglycerides, cholesterol, HDL cholesterol, and insulin excursions did not differ between treatments. Subjective appetite measures of satiety were significantly increased after HMS; however, no effects on energy intake were observed during the ad libitum meal.
Evidence strength: Acute satiety data are supportive but effects on long-term energy intake and body weight in humans are modest and inconsistent. Animal data are more robust, but translation to humans remains uncertain. This area requires larger, longer trials.
Beyond glucose regulation and gut health, RS impacts diverse metabolic and immunological pathways. It modulates bile acid metabolism, gut immune responses, and systemic inflammatory markers such as C-reactive protein and interleukins.
Short-chain fatty acids (SCFAs) are the most abundant microbial metabolites in the colonic lumen and are mainly produced by the microbial fermentation of prebiotics, such as dietary fiber. Reviews focus on the preventive and immunomodulatory effects of SCFAs on autoimmunity. Specifically, those who had greater changes in SCFA production following treatment with SCFA-producing starch exhibited elevated levels of glycemic control with increased levels of regulatory T and B cells.
Evidence strength: Immune and inflammatory biomarker data in humans are largely preliminary, derived from small trials or as secondary endpoints. The mechanistic basis via SCFA–immune receptor interactions is well-established in preclinical models; clinical translation requires further study.
Amylose is not sold or regulated as a single-compound supplement; it is consumed principally as high-amylose starch preparations. The following doses are those employed in published human studies:
In summary, intervention doses across human studies have ranged from approximately 13.5 g/day to 45 g/day of high-amylose starch preparations, administered over periods of 4 to 26 weeks, in forms including cookies, yogurt, custard, and protein drinks. No standardised supplemental dosage for general use has been established by a regulatory body.
High-amylose starch has been well tolerated in human clinical trials at doses ranging from approximately 13.5 to 45 g/day. There were no differences between conditions in the frequencies of reported adverse events. Most adverse events were mild and not related to consumption of the study product. There were no differences in mean scores between conditions for the individual symptom components of the GI tolerability questionnaire.
The primary dose-related adverse effect is increased intestinal gas production due to fermentation in the colon. Scores indicating that flatulence occurred "more than usual" or "much more than usual" were 9.1% for the control condition, 9.1% for the 15 g/d HAM-RS2 condition, and 33.3% for the 30 g/d HAM-RS2 treatment (p = 0.014 vs. control). There were no differences between conditions in scores indicating "more than usual" gas/bloating, nausea, loose stools, constipation, or GI cramping.
The mechanism of these gastrointestinal effects is colonic bacterial fermentation. The primary mechanism underlying these adverse effects is microbial fermentation, which generates gases and organic acids that increase intraluminal pressure and stimulate visceral sensory pathways. These symptoms generally subside over time as participants adapt, particularly among those with higher baseline levels of beneficial bacteria and habitual diets rich in whole grains.
Alpha-glucosidase inhibitors (e.g., acarbose) and pharmaceutical starch-blocking agents work by inhibiting enzymes involved in starch digestion. Concurrent use of these agents with large amounts of resistant starch preparations could theoretically compound gastrointestinal effects including abdominal pain, diarrhea, and flatulence, as both the drug and the dietary substrate impair normal carbohydrate digestion by overlapping mechanisms. This is documented as a clinically relevant pharmacodynamic consideration, though direct clinical trials examining the interaction specifically with purified amylose or high-amylose starch products are not widely published.
Commercial high-amylose starch products are predominantly derived from maize (corn). Individuals with confirmed corn allergy should exercise caution with corn-derived high-amylose starch preparations. Potato-derived or wheat-derived high-amylose starches represent alternative sources but introduce allergen considerations of their own.
In humans, the digestibility of HAMSB is 68% (w/w), and 60% of butyrate molecules attached to the starch backbone are absorbed by the colon. The modified (esterified) forms such as HAMSB have undergone safety assessment in human trials. The main objective of the pilot study on HAMS-AB in recently diagnosed type 1 diabetes was to assess the safety of HAMS-AB and its effect on the gut microbiome. These modified forms have been described as well tolerated in short-term studies, though long-term safety data in special populations remain limited.
Most human safety data derive from trials of 4–26 weeks' duration with relatively small sample sizes. Long-term safety of continuous supplementation at high doses has not been characterized in large-scale studies. Furthermore, most trials have used specific branded preparations (e.g., Hi-Maize 260, HAMSB), and safety findings may not be fully generalisable to all amylose-rich products.
Health conditions that Amylose may help support.
Body systems that Amylose may help support.
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