IngredientsIsomaltooligosaccharide (IMO) is a mixture of short-chain carbohydrates which has a digestion-resistant property. Isomalto-oligosaccharides (IMO) are glucose oligomers with α-D-(1,6)-linkages, including isomaltose, panose, isomaltotriose, isomaltotetraose, isomaltopentaose, nigerose, kojibiose, and higher branched oligosaccharides.
The majority of glucose oligosaccharides found in IMO consist of 3–6 monosaccharide units linked together; however, disaccharides as well as longer polysaccharides (up to 9 units) are also present. Although the term "isomalto-oligosaccharides" refers strictly to the glucosyl oligosaccharides containing α-(1-6)-linkages, commercially available IMO preparations are generally accepted as a mixture of glucosyl oligosaccharides with both α-(1-6) and α-(1-4)-linkages.
The CAS registry number for isomaltose (the primary disaccharide component) is 499-40-1. The systematic chemical name for the simplest component, isomaltose, is 6-O-α-D-glucopyranosyl-D-glucopyranose. The broader mixture is most commonly referred to in scientific literature by the acronym IMO or IMOs. Oligosaccharides are carbohydrate chains typically containing 3 to 10 sugar (monosaccharide) units joined together by glycosidic bonds, sometimes including disaccharides and smaller chains than polysaccharides.
Isomalto-oligosaccharides are a normal part of the human diet and occur naturally in fermented foods, such as fermented sourdough breads and kimchi. The disaccharide isomaltose is also present in rice miso, soy sauce, and sake. In fermented foods such as miso, sake, soy sauce, beer, and honey, minimal concentrations of naturally occurring IMOs can be observed.
Because of the high market demand for products containing IMOs, obtaining a sufficient supply of naturally occurring IMOs for commercial use is not economically feasible. Because of a confusion over nomenclature, disaccharides have frequently been described as IMO; however, to truly be called an "oligosaccharide," the molecules must have a degree of polymerization (DP) of three or more. Historically, the best-documented source of IMO was found in sourdough breads, wherein proper oligosaccharides are produced.
Isomalto-oligosaccharide is formed by enzyme-catalyzed hydrolysis of starch from different cereal crops (wheat, barley, corn), pulses (lentils, peas), rice, tapioca (cassava), potato, and other starch sources. Enzymes, including alpha-glucosidase, alpha-amylase, and pullulanase, hydrolyse the polysaccharides in starch to produce mono-, di-, tri-, and other smaller oligosaccharides with alpha-1,4 and alpha-1,6 glycoside linkages.
This process is followed by transglycosylation, which converts the α-(1→4) glycosidic linkages in starch to indigestible α-(1→6) glycosidic linkages, producing pure forms of IMOs with varying degrees of glucose polymerization, including isomaltose, panose, isomaltotriose, and other higher oligosaccharides. Commercial IMOs are produced enzymatically from starch hydrolysates (maltose and maltodextrins) through the action of the α-transglucosidase (EC 2.4.1.24) from Aspergillus sp.
IMO is a sweet-tasting, high-density syrup which could be spray-dried into powder form. Ingredion describes it as a colorless or light yellow, transparent syrup. IMO has a high moisturizing property and can inhibit the crystallization of sucrose. IMO shows higher permeability than sucrose. The sweetness of IMO is not high, about 40–50% sucrose. The viscosity of IMO is higher than that of sucrose, which makes it easier to ensure structural stability.
IMO likely contains fewer than 2 calories per gram, and its relative sweetness compared to sucrose is reported at 60–70%. Commercially available IMOs are a mixture of oligosaccharides with the main degrees of polymerization (DPs) ranging from 2 to 10.
IMOs are found naturally in soy sauce, sake, rice miso, honey, and fermented foods such as kimchi and sourdough bread, and are commercially produced from starch-derived sources. In Asia, IMOs have been used as a functional food and sweetener for more than three decades. They have a longstanding history of being utilized as prebiotic fiber sweeteners in Asian cuisine for over three decades.
IMO itself is a modern food science innovation; however, its natural precursors—found in traditional fermented Asian foods—have been part of human diets for centuries. These naturally occurring oligosaccharides were consumed as part of fermented soy and rice products, and their beneficial effects on digestion and gut flora were noted long before prebiotics were scientifically defined.
The roots of IMOs can be traced back to traditional medicinal practices, particularly in East Asia, where naturally occurring oligosaccharide-rich substances were consumed for their perceived health benefits. For centuries, extracts from sources such as barley, rice, and various tubers—now known to be rich in oligosaccharides—were incorporated into remedies to improve digestion, alleviate gastrointestinal discomfort, and boost overall vitality.
It should be noted that these traditional accounts are secondary-source reconstructions; no primary historical documents from East Asian medical traditions specifically identify "isomalto-oligosaccharides" by name, as the compound was not chemically characterized until the modern era. The connection between traditional fermented-food cultures and IMOs is inferred from the known natural presence of IMOs in those foods.
IMO gained prominence in the late 20th and early 21st centuries with advances in carbohydrate chemistry and enzymology, allowing manufacturers to produce purified, food-grade IMOs for commercial use. Its utility as a functional sweetener and prebiotic fiber positioned it as a popular ingredient in the health food and sports nutrition industries, especially in low-carb, high-protein, and digestive wellness products.
Chemically, IMO is a mixture of glucose oligomers with alpha-(1-6)-linkages such as isomaltose, panose, isomaltotriose, and isomaltopentose. IMOs are glucosyl saccharides that contain one or more α-1,6-glycosidic linkages sometimes accompanied by α-1,4, α-1,3 and/or α-1,2 linked glycosidic bonds. Depending on the production method, the structure of the IMO molecules can vary significantly.
The digestibility of IMO is a scientifically debated topic. Human digestive enzymes such as isomaltase and maltase/glucoamylase partially hydrolyze IMOs. The manufacturing process determines the degree of polymerization (DP) and the α-(1→4):α-(1→6) linkage ratio in IMOs and the digestibility by brush border enzymes in the small intestine. IMOs that contain a component with higher DP and α-(1→6) linkages are less digestible by human digestive enzymes.
Consequently, these indigestible IMOs enter the colon and are metabolized by gut microbiota to produce short-chain fatty acids (SCFAs), which are largely responsible for the beneficial effects of fibers.
However, an important caveat has emerged from recent research. IMOs have been characterized as dietary fibers that resist digestion in the small intestine; however, previous studies suggested that various α-glycosidic linkages in IMOs were hydrolyzed by mammalian α-glucosidases. One study investigated the hydrolysis of IMOs by small intestinal α-glucosidases from rat and human recombinant sucrase–isomaltase complex compared to commonly used fungal amyloglucosidase (AMG) in vitro. Interestingly, mammalian α-glucosidases fully hydrolyzed various IMOs to glucose at a slow rate compared with linear maltooligosaccharides, whereas AMG could not fully hydrolyze IMOs because of its very low hydrolytic activity on α-1,6 linkages. This suggests that IMOs have been misjudged as prebiotic ingredients that bypass the small intestine due to the nature of the assay used. Instead, IMOs can be applied in the food industry as slowly digestible materials to regulate the glycemic response and energy delivery in the mammalian digestive system.
The evidence suggests that IMO is highly digestible with a small residual portion reaching the colon (estimated at 10%) and affecting the microbiota.
Prebiotics are defined as "non-digestible food ingredients that may beneficially affect the host by selectively stimulating the growth and/or activity of a limited number of bacteria in the colon." Oligosaccharides that are not digested and absorbed in the small intestine pass through to the colon where they are fermented by Bifidobacteria, thus enhancing the proliferation of the bacteria. In this respect, fermentable oligosaccharides may be considered prebiotics.
IMOs selectively promote the proliferation of beneficial gut bacteria, including Bifidobacterium and Lactobacillus species, while increasing the production of short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate. Based on metatranscriptome analysis, members of Bacteroides, Lactobacillus, and Bifidobacterium were the predominant degraders of IMOs.
Functional oligosaccharides are excellent microbiota-accessible carbohydrates (MACs) possessing important prebiotic properties for intestinal health through their fermentation in the gut. The mechanism of action is predominantly attributed to acting as carbon sources for specific probiotics, promoting short-chain fatty acids production, and regulating the gut microbiota. IMOs exhibit prebiotic properties that stimulate the growth of beneficial bacteria. In addition, they can modulate immune responses, enhance disease resistance, and improve lipid metabolism and liver and kidney functions.
Evidence base: Several human and in vitro studies. Overall evidence is moderate but limited by small sample sizes and variability of commercial IMO preparations.
Isomalto/malto-polysaccharides (IMMPs) are a novel type of soluble dietary fibres with a prebiotic potential promoting growth of beneficial microbes in the gut. However, the mode of action of IMMPs remains unknown. Previous studies on IMMPs showed an increase in total bacteria, especially lactobacilli, and higher production of short chain fatty acids (SCFA) when IMMPs were fed to rats or used during in vitro fermentation.
Metatranscriptomic studies showed that active microbial community dynamics during fermentation varied depending on the type of IMMP used, and that the observed changes were reflected in the community gene expression profiles. Members of Bacteroides, Lactobacillus, and Bifidobacterium were the predominant degraders of IMOs.
Certain populations, such as Asians, may experience beneficial changes in the microbiota and changes in laxation for constipated individuals with a sufficient dose, but no evidence exists to confirm these effects in non-Asian populations. Variability in IMO compositions from different manufacturers may be one of the reasons for the conflicting evidence on digestibility.
While relative abundance and gene expression of some of the beneficial bacteria increased with the presence of IMMPs, the exclusive use of these prebiotics put a selective pressure on other beneficial microbes. This highlights that the prebiotic effect is not uniformly selective and warrants further investigation in well-powered human clinical trials.
Evidence base: Several small human trials, primarily in Asian populations. Evidence is preliminary to moderate.
A previous study found that 30 days of IMO supplementation resulted in a twofold increase in defecation frequency, wet stool volume, and dry stool weight in a group of healthy participants. Similarly, constipated patients who received 10 g/day of IMOs for 4 weeks experienced an increase in defecation frequency and output of wet and dry stools.
Unlike fructose, which is widely used in the treatment of IBS with predominant constipation, IMO is unable to increase intestinal gas production and therefore will not worsen abdominal distension. A placebo-controlled, diet-controlled trial showed that treatment with an IMO-rich diet for 4–8 weeks in the elderly with constipation increased the frequency of spontaneous bowel movements.
Consumption of IMO effectively improved bowel movements, stool output, and microbial fermentation in the colon without any adverse effects in elderly people.
Importantly, the EFSA Panel on Dietetic Products, Nutrition and Allergies examined health claim submissions in 2010. The Panel concluded that a cause and effect relationship has not been established between the consumption of isomalto-oligosaccharides and an increase in the frequency of daily bowel movements. The Panel also concluded that a cause and effect relationship has not been established between the consumption of isomalto-oligosaccharides and reduction of post-prandial glycaemic responses. EFSA's conclusions reflect the limited and sometimes inadequate quality of clinical data submitted at that time.
Evidence base: Mixed and contested. Recent mechanistic data challenge earlier assumptions. Overall evidence is conflicting and preliminary.
The majority of the studies that tested IMOs in Asian populations had conflicting evidence on their digestibility and fermentability. The reported Glycemic Index (GI) for IMO is 34.66 ± 7.65 (on a scale of 1–100), which represents a low GI.
Two randomized, double-blind, placebo-controlled, crossover human studies (described in Gourineni et al., 2018) assessed IMO glycemic properties. In the first study (n = 26), participants' breath hydrogen over 24 h, gastrointestinal tolerance, and glycemic and insulinemic response to BIOLIGO™ IL5040 isomaltooligosaccharide were measured. In another study (n = 10), participants' two-hour post-prandial glycemic response to BIOLIGO™ IL5040 and BIOLIGO™ IL7010 isomaltooligosaccharide was measured compared to dextrose (control). The IMOs differed in the composition of mono and disaccharide sugars. IMO syrup dose was matched for 50 g of total carbohydrates. Mean composite gastrointestinal score was not significantly different (p = 0.322) between the control (1.42) and IMO (1.38).
The relationship between IMO intake and type 2 diabetes mellitus has been investigated clinically. A previous study evaluated the glycemic and insulin responses of healthy subjects to whey protein bars containing IMOs as a carbohydrate source. A randomized crossover study with 10 participants showed that the glycemic response was significantly lower in the first 60 min after the ingestion of whey protein bars compared with a dextrose reference.
A critical development in understanding IMO digestibility came from an in vitro mechanistic study (Gänzle & Follador, 2022, published in Food Chemistry). Mammalian α-glucosidases fully hydrolyzed various IMOs to glucose at a slow rate compared with linear maltooligosaccharides, whereas AMG could not fully hydrolyze IMOs because of its very low hydrolytic activity on α-1,6 linkages. This suggests that IMOs have been misjudged as prebiotic ingredients that bypass the small intestine due to the nature of the assay used. Instead, IMOs can be applied in the food industry as slowly digestible materials to regulate the glycemic response and energy delivery in the mammalian digestive system.
Evidence base: Limited human evidence; most data from animal studies. Evidence is weak and preliminary.
One published study (Wang et al., 2001) investigated the use of isomalto-oligosaccharide in the treatment of lipid profiles and constipation in hemodialysis patients. Long-term supplementation of isomalto-oligosaccharides improved colonic microflora profile, bowel function, and blood cholesterol levels in constipated elderly people in a placebo-controlled, diet-controlled trial (Nutrition, 2011).
IMOs can modulate immune responses, enhance disease resistance, and improve lipid metabolism and liver and kidney functions, according to animal and mechanistic studies. Human clinical evidence for lipid-lowering effects remains limited and underpowered.
Evidence base: Primarily animal studies, with limited human data. Evidence is preliminary.
High-fat diet (HFD)-induced obesity models have shown that IMOs, administered alone or in combination with other compounds, exhibit potent antiobesity effects, making them promising agents in the treatment of obesity and its associated complications. Moreover, IMOs exhibit preventive effects against HFD-induced metabolic dysfunction by modulating gut microbiota and short-chain fatty acid levels, thereby ameliorating symptoms.
A mouse study (PubMed ID 28668709) evaluated IMOs in combination with green tea extract against high-fat diet (HFD)-induced metabolic alterations. The combination of GTE and IMOs effectively prevented HFD-induced adiposity and lipid accumulation in liver and muscle while normalizing fasting blood glucose, insulin, glucagon, and leptin levels. It also prevented leaky gut phenotype and HFD-induced increase in circulating lipopolysaccharides and pro-inflammatory cytokines (e.g., resistin, TNF-α, and IL-1β) and reduction in anti-inflammatory cytokines (e.g., adiponectin and IL-6). These findings are in mice and should not be extrapolated directly to humans.
Evidence base: Animal models and in vitro studies only. No robust human clinical trials identified for IBD specifically.
IMOs can reduce IBD and alleviate hyperlipidemia based on findings from animal models. In animal studies, dietary intake of IMOs attenuated the intestinal inflammatory response, improved the intestinal microecological environment, and slowed the development of chemically induced early colorectal carcinogenesis in rats. This work provides a theoretical basis and technical support for the clinical prevention or treatment of colorectal cancer with prebiotics. These results come from a rat carcinogenesis model and require validation in human studies.
Evidence base: In vitro and animal studies; mechanistic rationale is well-established.
IMO is not fermentable by normal mouth bacteria, so it does not promote tooth decay. IMO-added confectionery does not contribute to dental caries. These properties follow from IMO's resistance to fermentation by oral microbiota, distinguishing it from sucrose and other fermentable sugars.
Isomalto-oligosaccharide is a food ingredient that is added to various foods as either powder or a syrup. IMO is used as a sweetener in biscuits, cakes, crackers, nutritional food bars, edible ices, tofu, powdered milk, flavoured drinks, sweet sauces, toppings and syrups, ready-to-eat savouries and snacks.
The following dosages are as stated in the referenced studies and regulatory sources:
IMOs have been Generally Recognized as Safe (GRAS) by the United States Food and Drug Administration (FDA) since 2016, and accepted as novel food ingredients by numerous jurisdictions around the world including Health Canada in 2012, the European Food Safety Authority (EFSA) in 2010, and Food Standards Australia New Zealand (FSANZ) in 2017.
The US Food and Drug Administration and other global regulatory agencies have generally recognized IMOs as safe, with a maximum daily intake of 30.0 g/day. The U.S. FDA has already issued "no questions" responses regarding the conclusion that other commercially available preparations of IMOs are GRAS for their intended uses in foods (GRN 246; GRN 674).
Studies have shown that IMO has been found to be most tolerable with the least adverse effects compared to other short-chain resistant oligosaccharides. IMO is less fermentable by normal intestinal bacteria than fructooligosaccharides (FOS). This suggests a potentially lower risk of gas and bloating compared to FOS at equivalent doses.
The EFSA Panel notes that conservative intake estimates at the 95th percentile exceed the dose of 120 g/day for which tolerability has been demonstrated. However, considering the source, compositional characterisation, production process, and nature of the novel food, as well as the available nutritional and toxicological data, the Panel considers that the novel food does not present safety concerns under the proposed conditions of use.
A significant safety and labeling concern centers on whether commercial IMO truly functions as a dietary fiber. Earlier studies examined breath hydrogen response to IMO up to 25 g/day for 7 h in healthy adults and reported no effect on breath hydrogen, reflecting insufficient evidence of fermentation. In another study, increase in blood glucose indicated IMO to be highly glycemic.
The FDA has addressed this issue from a labeling perspective. According to the FDA, dietary fiber is defined as non-digestible soluble and insoluble carbohydrates (with 3 or more monomeric units), and lignin that are intrinsic and intact in plants; isolated or synthetic non-digestible carbohydrates (with 3 or more monomeric units) determined by FDA to have physiological effects that are beneficial to human health. Based on this definition, industrial IMO does not qualify as a dietary fiber, since it is not intrinsic and intact in plants, nor has it been shown to have beneficial physiological effects as defined by the FDA.
Different commercial production methods of IMO result in variability of its carbohydrate composition, digestibility, caloric content, and utilization by intestinal bacteria. Consumers and researchers should be aware that the term "IMO" encompasses a range of preparations with meaningfully different functional properties depending on their degree of polymerization and α-(1→6) linkage content.
For manufacturing IMO on a commercial scale, food industries use starch processed from cereal crops like wheat, barley, pulses (peas, beans, lentils), oats, tapioca, rice, potato, and others. This variety in sources could benefit consumers who have allergies or hypersensitivity to certain cereal crops. Individuals with celiac disease or wheat/barley allergies should verify the source starch used in any specific IMO product, as gluten-containing grains are among the raw material options.
The EFSA NDA Panel (2010) reviewed two proposed health claims for IMO. One reference submitted for the glycemic claim was in Chinese and unavailable to the Panel, and the second reported on an intervention study in dogs on post-prandial glucose concentrations. The Panel considers that while effects shown in animal studies may be used as supportive evidence, human studies are required for the substantiation of a claim, and that the evidence provided in animal studies alone is not sufficient to predict the occurrence of an effect of isomalto-oligosaccharides consumption on the reduction of post-prandial glycaemic responses in humans. Both health claims—for glycemic reduction and for increased bowel movement frequency—were rejected by EFSA on grounds of insufficient human clinical evidence.
On PubMed, using the term "isomaltooligosaccharides" retrieved 19 articles published in 2023, with most being reviews, in vitro, or animal studies. There is limited information regarding the efficacy of IMOs against gastrointestinal diseases. The overall evidence base for IMO's health benefits in humans remains limited in both quantity and methodological quality, with most favorable findings coming from small trials, animal models, or in vitro systems. Large, well-controlled randomized clinical trials in diverse populations are needed to substantiate the health claims commonly associated with this ingredient.
Health conditions that Isomalto-oligosaccharide may help support.
IMO supplementation at doses used in clinical trials (10–30 g/d) produced well-tolerated, mild gastrointestinal side effects including bloating in some studies. In IBS rat models, IMO reduced visceral pain scores. IMO's low FODMAP classification suggests it is less likely to cause fermentation-related discomfort than other prebiotics.
IMO fiber may suppress appetite by increasing gastric volume and promoting release of satiety hormones including GLP-1 and CCK. Animal studies show modulation of hypothalamic appetite-regulating genes. Human evidence is indirect and based on subjective appetite ratings in bar/food matrix studies.
IMO elicits a lower postprandial glycemic response than dextrose, though it is not entirely non-digestible. Small human trials show modest reductions in fasting plasma glucose when IMO is combined with high-protein diets. EFSA has reviewed glycemic claims for IMO. The evidence suggests partial benefit, with the caveat that IMO has a measurable glycemic impact.
Clinical trials in constipated elderly subjects and hemodialysis patients show IMO supplementation significantly reduces total cholesterol and increases HDL-C. IMO-fortified cookie trials in hyperlipidemic subjects also demonstrated cholesterol reduction. The mechanism likely involves SCFA inhibition of hepatic cholesterol synthesis.
IMO modulates systemic and gut inflammation primarily through its prebiotic effects on microbiota composition and SCFA production. In animal models, IMO prevented HFD-induced increases in pro-inflammatory cytokines (TNF-α, IL-1β) and reduced metabolic endotoxemia. Human clinical data on inflammation endpoints are indirect.
Multiple human clinical trials demonstrate that IMO at 10–30 g/d significantly improves bowel movement frequency, stool output, and constipation symptoms. Effects appear time-dependent and attenuate after discontinuation. IMO is likely one of the most clinically validated uses for this ingredient.
IMO ingestion stimulates incretin hormone (including GLP-1) secretion comparably to dextrose in healthy adults, based on a dedicated crossover study. IMO's prebiotic fermentation also increases SCFA production, which promotes GLP-1 release from L-cells. The effect may support satiety signaling.
IMO functions as a prebiotic, selectively stimulating growth of Bifidobacterium, Lactobacillus, and Bacteroides in the colon. Clinical and in vitro studies consistently show increased beneficial bacteria counts and SCFA production. These microbiota shifts underpin most of IMO's downstream metabolic and gastrointestinal benefits.
Animal models consistently show IMO prevents HFD-induced adiposity and weight gain, modulating hypothalamic appetite-regulating genes. A small human single-arm trial found IMO combined with high-protein diet reduced BMI, body fat percentage, and waist circumference. Evidence remains preliminary in humans.
A rat model of IBS demonstrated that IMO reduced visceral hypersensitivity and repaired ileal epithelial ultrastructural damage. IMO is classified as low FODMAP, making it generally tolerated by IBS patients. Human clinical trial evidence in IBS populations is limited.
IMO has been explored for IBD based on its ability to restore SCFA-producing bacteria, support tight junction integrity, and reduce mucosal inflammation in preclinical colitis models. The 2024 PMC review identifies IBD as a key therapeutic target for IMO. Human clinical data in IBD populations are not yet available.
Animal models consistently show IMO prevents HFD-induced insulin resistance and normalizes insulin and glucagon levels. Human clinical data are limited but suggest a modest improvement in fasting glucose. IMO's prebiotic action on gut microbiota may contribute to improved insulin signaling through SCFA-mediated pathways.
IMO has been shown in animal models to prevent high-fat diet-induced intestinal hyperpermeability (leaky gut phenotype) by supporting tight junction integrity and reducing circulating LPS. The mechanism involves SCFA-mediated support of the intestinal epithelial barrier. Direct human clinical trials on gut permeability endpoints are lacking.
IMO addresses multiple components of metabolic syndrome—dyslipidemia, insulin resistance, obesity, and gut dysbiosis—in animal models. The 2024 PMC review identifies metabolic syndrome as a key potential application. Human clinical trial evidence is indirect, derived from individual MetS component outcomes.
IMO supplementation has been shown to reduce fasting triglyceride levels in hemodialysis patients and in hyperlipidemic subjects consuming IMO-fortified foods. Animal studies corroborate reduced hepatic lipid accumulation. SCFA production from IMO fermentation may inhibit hepatic triglyceride synthesis.
Body systems that Isomalto-oligosaccharide may help support.
Go back