IngredientsPropolmannan is the trade/functional name for a highly purified preparation of konjac glucomannan (KGM), the primary polysaccharide extracted from the underground corm (tuber) of Amorphophallus konjac K. Koch (family Araceae). The most commercially prominent form is marketed under the registered trademark Propol® A, manufactured by Shimizu Chemical Corporation of Japan. Propol® A propolmannan is described as a highly pure, natural soluble fiber created from Amorphophallus konjac-derived glucomannan using proprietary processing techniques. A separate proprietary preparation, marketed under the brand name LuraLean, identifies its propolmannan as sourced from Amorphophallus japonica, described as a rare tuberous plant. LuraLean consists of propolmannan, a highly purified, natural dietary fiber patented in 33 countries, sourced from Amorphophallus japonica, found in the mountainous regions of northern Japan. In the scientific literature, propolmannan is consistently treated as a refined, high-purity variant of konjac glucomannan; all peer-reviewed evidence for the ingredient is drawn from the broader body of konjac glucomannan research.
Common synonyms and related names include: konjac glucomannan, konjac mannan (KJM), konjac-mannan (KM), glucomannan, konnyaku flour, and — in food applications — konjac gum (EU food additive E 425). It is also referred to as konjac root fiber; food-form deliveries include shirataki noodles, konjac flour, and konjac gel.
Amorphophallus konjac has long been used in China, Japan, and Southeast Asia as a food source and as a traditional medicine. Of the 170 species of Amorphophallus, A. konjac has the longest history of use in the region. The plant is grown in warm subtropical to tropical areas of East and Southeast Asia, from China and Japan south to Indonesia and Vietnam. Major cultivation occurs in China and Japan, with production expanding into other Southeast Asian countries. The plant prefers warm subtropical to tropical climates, requiring well-drained, nutrient-rich soils. Yunnan, China, holds a special place in konjac's origin story; today, over 40% of global konjac originates from Yunnan.
The part of the plant used is the corm (an enlarged underground storage organ sometimes called the tuber). Mature konjac tubers contain konjac glucomannan (KGM, 49%–60%), starch (10%–30%), fiber (2%–5%), crude protein (5%–14%), soluble sugars (3%–5%), ash (3.4%–5.3%), and small amounts of alkaloid and saponin. The content of KGM in corms is about 40% of the dry weight, but highly purified flours can contain greater than 98% KGM.
Propolmannan/konjac glucomannan is commercially available in several forms:
Due to its high thickening, good film formation, excellent gelation, good biocompatibility, and biodegradability, as well as its colorless, odorless, and non-toxic characteristics, KGM is generally regarded as safe (GRAS) as a food additive by the FDA. The flour produced from konjac corms is used as a gelling and thickening agent and is a permitted food ingredient in Europe under E 425.
A distinguishing feature of propolmannan preparations such as Propol® A is the removal of natural degrading enzymes. Natural enzymes that would otherwise cause it to break down during digestion have been removed, which is intended to preserve the molecular integrity and viscosity of the fiber through the gastrointestinal tract. The fiber has been studied for its viscosity and for its stability through the digestive tract.
Konjac (moyu) was first domesticated in Southwest China about 2,000 years ago, where Yi people and other early cultivators developed methods to detoxify the naturally irritating corm through repeated boiling and the use of alkaline ash water. Its historical significance is underscored by its first documentation in the Shen Nong Materia Medica during the Western Han Dynasty, highlighting its longstanding role in ancient Chinese medicine.
In traditional Chinese medicine (TCM), a gel prepared from the flour has been used for detoxification, tumor-suppression, blood stasis alleviation, and phlegm liquefaction; for more than 2,000 years it has been consumed by the indigenous people of China for the treatment of asthma, cough, hernia, breast pain, burns, as well as haematological and skin disorders. From traditional uses in Chinese medicine to its integral role in local diets as konjac blocks resembling tofu, Yunnan showcases the deep connection between culture, sustenance, and wellness.
Konjac is believed to have originated in the Yunnan region of China and was introduced to Japan around the 6th century. The plant was initially cultivated for its medicinal properties, as it was thought to possess healing powers. After arriving from China, konjac became widely used in Japan's Buddhist temples. Monks valued it for being vegetarian and easy to digest, so it naturally became a star ingredient in shojin ryori, the traditional temple cuisine. Its smooth, jiggly texture made it a unique and filling alternative to meat.
Konjac has been used in Japan since the 6th century as a supposed medicinal food. Japanese documents from around the 18th century mention its intestinal cleansing property. Nakajima Toemon developed a method to produce konjac flour in 1776, which is more durable for transportation and storage, contributing to wider consumption. Konjac slowly earned a place in cooking during the Kamakura period (1185–1333), before becoming widespread from the 17th century onwards. Since 1776, when the Japanese perfected the technique of making flour from konjac, it caught on to such an extent that it almost became more popular than rice.
Glucomannan has been used as a dietary fiber for more than 1,000 years in eastern cultures. Traditionally used in East Asian cuisines as a thickening and gelling agent, konjac glucomannan has more recently garnered attention as a functional dietary fiber in nutritional supplements.
Traditional preparations centered on the corm flour. The raw corm contains irritating compounds (calcium oxalate crystals), so processing — including boiling and the addition of alkaline agents such as ash water — was necessary to render it safe for consumption. The processed flour was then formed into blocks (konnyaku), jellies, noodles (shirataki), and similar foods. The process involves mixing konjac powder from the root with water and a gelling ingredient, which results in the mixture solidifying into a firm, rubbery cake.
Traditional therapeutic applications encompassed digestive complaints (constipation, intestinal cleansing), detoxification, respiratory ailments (asthma, cough), blood-related and skin disorders, and tumor suppression, as documented in TCM sources. Historically, konjac has also been used in traditional Chinese medicine for digestive support, detoxification, and other therapeutic applications.
Konjac glucomannan (KGM) consists of 1,4-linked D-mannose and D-glucose residues, forming a high molecular weight polysaccharide. The mannose to glucose ratio is approximately 1.6:1, and it is believed that there are no block sequences of glucose or mannose along the chain. The main chain has branches, approximately every 10 residues, of up to 16 sugar units linked to the C3 position of the glucose and mannose.
The molecular weights of KGM range from 200 to 2,000 kDa (kilodaltons). Propolmannan is claimed to boast the highest molecular weight of any water-soluble fiber in the natural world, a characterization consistent with reported molecular weight ranges for highly purified preparations. Glucomannan from the konjac plant is a glucose-mannose polysaccharide in which 5–10% of the sugars are acetylated. These acetyl groups are distributed along the chain and influence the fiber's solubility, viscosity, and gel-forming behavior.
The viscosity of KGM solution is greater than that of guar gum, one of the most viscous soluble dietary fibers. It forms a highly viscous sol when constituted with water at concentrations of pure glucomannan above 1.0% w/w and is the only biopolymer currently known to form an aqueous gel at room temperature. The gel forms within a few minutes of mixing with water.
Standard konjac flour undergoes multiple purification steps to yield propolmannan-grade material. Using cutting-edge technology, it has been reduced to a special particle size that maximizes density while remaining in desirable viscous form. A 500 mg capsule of propolmannan contains more fiber than the same milligram amount from other plants, and natural enzymes that would otherwise cause it to break down during digestion have been removed. KGM is a high-molecular-weight polysaccharide that was originally extracted from the corms (underground storage organs) of Amorphophallus konjac.
Three physicochemical properties drive the physiological actions of propolmannan:
Upon ingestion with water, propolmannan/KGM rapidly absorbs fluid and swells into a large, viscous gel mass within the stomach. This mechanical bulking effect slows gastric emptying, prolonging the sense of fullness and potentially delaying nutrient absorption. The potential mechanism of action is to increase satiety due to a delay in gastric emptying caused by the "mass effect" of the viscous, gel-like mass forming in the stomach and slowing down gastrointestinal transit time.
Glucomannan has the characteristic of reducing triglycerides as well as total and LDL cholesterol, an effect that seems to be determined by its viscosity. The highly viscous gel formed by KGM in the small intestine binds bile acids, preventing their reabsorption in the terminal ileum. The liver must then synthesize new bile acids from circulating cholesterol, reducing serum cholesterol levels — a mechanism shared with other viscous soluble fibers such as psyllium and oat beta-glucan. The viscous gel formed by glucomannan slows the digestion and absorption of carbohydrates, which stabilizes blood glucose levels, particularly for individuals with insulin resistance or type 2 diabetes.
By forming a viscous gel in the GI tract, KGM slows the rate of carbohydrate digestion and glucose absorption, thereby attenuating postprandial blood glucose and insulin excursions. KG has been shown to promote health by reducing glucose, cholesterol, triglyceride levels, and blood pressure, thereby offering significant weight-loss advantages.
Propolmannan reaches the large intestine largely intact, where it undergoes fermentation by resident bacteria. KGM is degraded by gut microbiota-derived β-mannanase into small-molecule nutrients. As a prebiotic, KGM modulates gut microbiota composition, selectively fostering the proliferation of beneficial commensals and suppressing potential pathogens, thereby alleviating microbiota-related disorders. Microbiota fermentation of KGM produces metabolites; short-chain fatty acids (SCFAs) are particularly notable among these metabolites. They exert multifaceted beneficial effects, including metabolic regulation, intestinal barrier strengthening, and neuroprotective functions.
These effects are mediated through inhibition of inflammatory pathways (e.g., NF-κB, MAPK), modulation of lipid metabolism genes (e.g., CD36), and regulation of neurotransmitters (e.g., GABA, 5-HT). However, these specific mechanistic pathways have been primarily characterized in preclinical (animal and in vitro) models. Their clinical relevance in humans requires further investigation.
In animal studies, KGM treatment altered the gut microbiota, notably increasing Akkermansia muciniphila, a bacterium associated with weight loss, along with elevated levels of SCFAs such as butyrate and propionate. This weight-suppression effect was prebiotic rather than attributable purely to the physical properties of KGM, as antibiotic treatment abolished the weight-suppressing effect despite increased fecal volume. These are preclinical findings and cannot be directly extrapolated to the human clinical context.
Evidence strength: Moderate to strong (human RCTs and meta-analyses; EFSA-authorized health claim).
In 2009, the EFSA Panel on Dietetic Products, Nutrition and Allergies prepared a scientific opinion on health claims in relation to glucomannan (konjac mannan) and the maintenance of normal blood cholesterol concentrations. On the basis of the data available, the Panel concluded that a cause-and-effect relationship has been established between the consumption of glucomannan and the reduction of blood cholesterol concentrations. In order to bear the claim, a food should provide at least 4 g/day of glucomannan in one or more servings. The target population is the general population.
The foundational systematic review and meta-analysis by Sood, Baker, and Coleman (2008), published in the American Journal of Clinical Nutrition, remains the most cited quantitative synthesis. Several clinical trials have investigated the impact of glucomannan on plasma lipids, body weight, fasting blood glucose, and blood pressure, but have yielded conflicting results and had only modest sample sizes. The objective was to perform a meta-analysis of randomized controlled trials to better characterize its impact. The Sood 2008 meta-analysis of 14 RCTs documented approximately 16 mg/dL LDL reduction and approximately 19 mg/dL total cholesterol reduction. An intake of 1.24 to 15.1 g/day of glucomannan corresponded to a reduction of 15.9 mg/dL of LDL and 11.5 mg/dL of triglycerides compared to placebo.
A more recent meta-analysis, published in the American Journal of Clinical Nutrition (2017), updated the evidence on KJM and lipid targets. The update confirms the strong LDL-cholesterol–lowering effect of KJM. Although the optimal dosage remains undetermined, individual studies show that intakes of all observed doses of KJM (2.0–15.1 g/d) resulted in significant reductions in both LDL cholesterol and non-HDL cholesterol. It has been estimated that, on average, 5–10 g soluble dietary fiber is required to achieve a 5% reduction in LDL cholesterol, whereas the present analysis found that a median dose of 3 g KJM can produce a reduction in LDL cholesterol (−10%) that is double the projected average reduction.
A 2026 triple-blind, placebo-controlled RCT (preprint) in 40 adults with excess weight reported that participants who consumed konjac glucomannan significantly reduced LDL, total cholesterol, and atherogenic index, whereas participants in the control arm significantly reduced HDL and triglycerides. The cholesterol-lowering effect of KGM/propolmannan is the most consistently supported area of its evidence base.
Evidence strength: Contested — a regulatory approval exists, but subsequent meta-analyses show inconsistent or null results for weight loss specifically.
An early eight-week double-blind trial (Walsh et al., published in Int J Obes, 1984) involving 20 obese subjects assessed purified glucomannan. Glucomannan fiber (from konjac root) or placebo was given in 1-g doses (two 500 mg capsules) with 8 oz water, 1 hour prior to each of three meals per day. Results showed a significant mean weight loss (5.5 lbs) using glucomannan over an eight-week period. Serum cholesterol and LDL cholesterol were significantly reduced. No adverse reactions to glucomannan were reported.
In 2010, the European Food Safety Authority (EFSA) confirmed the positive effect of glucomannan on the reduction of body weight in overweight adults. The authorized EU claim specifies that glucomannan in three doses of 1 g each, together with 1–2 glasses of water, before meals and in the context of an energy-restricted diet contributes to the reduction of body weight.
However, subsequent meta-analyses have complicated this picture. The Sood 2008 meta documented modest approximately 0.8 kg weight loss. The Onakpoya 2014 systematic review and meta-analysis of 9 RCTs found no statistically significant weight loss attributable to glucomannan supplementation. Glucomannan may help to reduce body weight, but not body mass index, in otherwise healthy overweight or obese adults. Data in children are too limited for any conclusions to be drawn. An audit of the EFSA opinion found only four of nine studies in the general function opinion showed positive weight loss results, and the amount of weight loss achieved was described as unremarkable.
Three meta-analyses reported overall significant weight loss and one reported a nonsignificant effect. Taken together, the clinical evidence suggests that any weight-loss effect of propolmannan/glucomannan alone is modest at most, context-dependent (energy-restricted diet required), and not uniformly replicated. The cholesterol-lowering effect is better supported than the weight-loss effect.
Evidence strength: Moderate but inconsistent — effects demonstrated in some RCTs, no consistent consensus across studies.
A randomized controlled metabolic trial by Vuksan et al. (1999), published in Diabetes Care, enrolled 11 hyperlipidemic and hypertensive type 2 diabetic patients. A total of 11 hyperlipidemic and hypertensive type 2 diabetic patients treated conventionally by low-fat diet and drug therapy participated. All were randomly assigned to take either KJM fiber-enriched test biscuits (0.7 g/412 kJ [100 kcal] of glucomannan) or matched placebo wheat bran fiber biscuits during two 3-week treatment phases separated by a 2-week washout period. The diet conformed to National Cholesterol Education Program Step 2 guidelines while medications were maintained constant. Compared with placebo, KJM significantly reduced serum fructosamine (5.7%, P = 0.007), total:HDL cholesterol ratio (10%, P = 0.03), and systolic blood pressure (6.9%, P = 0.02). The authors concluded that KJM fiber added to conventional treatment may ameliorate glycemic control, blood lipid profile, and systolic blood pressure in high-risk diabetic individuals.
A meta-analysis of RCTs on glucomannan supplementation and type 2 diabetes, published on PMC (2023), noted: In 2010, the European Food Safety Agency confirmed that konjac glucomannan is beneficial for weight loss, reducing postprandial blood sugar, and lowering blood cholesterol concentration, and issued a health statement. However, the results in the relevant literature failed to reach a consensus. For example, konjac glucomannan significantly reduced fasting glucose in several studies, but Vuksan et al. showed that there was no significant difference.
The 2026 RCT (preprint) with 40 adults on personalized hypocaloric diets found that none of the two treatments promoted consistent changes in the glycemic profile. Overall, the evidence for glycemic benefits is suggestive in certain subpopulations (particularly type 2 diabetics) but not robust or consistent enough to constitute definitive clinical guidance.
Evidence strength: Moderate (supported by RCTs and consistent with mechanism; EFSA reviewed but did not authorize a claim for bowel function under Article 13.1 for all proposed uses).
The EFSA reviewed health claims related to konjac mannan (glucomannan) including maintenance of normal bowel function (ID 834, 1557, 3901) and decreasing potentially pathogenic gastro-intestinal microorganisms (ID 1558), pursuant to Article 13(1) of Regulation (EC) No 1924/2006. The constipation-relieving effect of glucomannan is mechanistically plausible (bulk-forming effect) and has been supported in human trials. Glucomannan has been reported to have hypocholesterolemic, hypoglycemic, hypoinsulinemic, and anti-constipatory effects. Emerging evidence highlights the role of konjac in supporting the proliferation of beneficial intestinal bacteria, such as Bacteroidetes and Akkermansia, which are associated with improved metabolic outcomes and negatively correlated with BMI.
KGM as a prebiotic polysaccharide exhibits multifaceted bioactivity. Current evidence suggests its potential to synergistically modulate metabolic pathways, gut microbiota composition, immune cell signaling, and neuroendocrine interactions. However, current clinical use is limited by dose-dependent adverse effects and interindividual response variability, which stem from different microbial communities. This necessitates personalized dosage strategies.
Evidence strength: Preliminary (observed in individual RCTs; not a focus of large dedicated meta-analyses).
In the Vuksan et al. trial, KJM significantly reduced systolic blood pressure by 6.9% (P = 0.02) compared with placebo. The 2026 RCT in 40 adults found no differences between the two study arms in the changes observed in blood pressure or the Framingham score. The Sood 2008 meta-analysis also examined blood pressure as an endpoint, with inconclusive results. Blood pressure reduction, while mechanistically plausible through weight and cholesterol effects, requires further dedicated investigation.
Evidence strength: Preliminary in humans; more developed in animal and in vitro models.
As a prebiotic, KGM modulates gut microbiota composition. It selectively fosters the proliferation of beneficial commensals and suppresses potential pathogens, thereby alleviating microbiota-related disorders. SCFAs produced by the fermentation of glucomannan also influence intestinal barrier function and immune responses, which may contribute to anti-inflammatory and metabolic effects. While the mechanistic model is well-developed, human clinical evidence directly linking propolmannan/glucomannan supplementation to clinically meaningful shifts in gut microbiota composition and health outcomes remains an active area of research with limited definitive trials.
Modern research has revealed that KGM can significantly lower plasma cholesterol levels, improve carbohydrate metabolism, and enhance bowel movement, thereby promoting gut health.
Propolmannan is commercially available as: powder (mixed with water before consumption), capsules, and tablets. Powder mixed in water before consumption is considered the safest form. Capsules expand more slowly than tablets but still require adequate water. Tablets carry the highest esophageal obstruction risk.
Minor adverse effects are normally GI-related and include diarrhea, flatulence, abdominal discomfort, and bloating. These effects are dose-dependent and typically self-limiting. Some studies reported gastrointestinal complications including abdominal pain, constipation, and diarrhea in the glucomannan group.
The most clinically significant safety concern associated with propolmannan/glucomannan is mechanical obstruction of the esophagus or gastrointestinal tract, particularly when the product is consumed in tablet form without sufficient water.
Several cases of severe esophageal obstruction due to glucomannan diet tablets have been reported. Seven cases were noted during 1984 and 1985 by the Australian Adverse Drug Reactions Advisory Committee. Four of these obstructions occurred in the proximal one-third of the esophagus. One patient developed mediastinitis due to perforation of the esophagus.
A case published in 2007 (Ann Pharmacother, Vanderbeek et al.) described a 37-year-old female who developed delayed esophageal obstruction after ingesting an over-the-counter diet aid containing glucomannan. The patient ultimately cleared the obstruction through forceful emesis, just prior to upper gastrointestinal endoscopy. The patient was noted to have an esophageal web during outpatient endoscopy. This case illustrates the potential dangers of glucomannan in patients with a history of upper gastrointestinal pathology.
The EU regulatory system documented these risks: The Panel noted that these restrictions have to be seen against the background of human cases of fatal accidents resulting from asphyxiation following the ingestion of jelly mini-cups confectionery containing the additive, and of severe adverse effects such as oesophageal obstruction after oral intake of the additive in the form of tablets without enough liquid.
As a consequence, the EU Register specifies a mandatory warning: A warning of choking is to be given for people with swallowing difficulties or when ingesting with inadequate fluid intake — with advice on taking with plenty of water to ensure the substance reaches the stomach.
Given the risk of esophageal and gastric obstruction, use is not recommended in patients with structural abnormalities of the esophagus or gut. Higher-risk users include small children, older adults with swallowing difficulty, and people with dysphagia. Higher-risk formats include mini-cup jelly, dry tablets, dry capsules, and poorly mixed powder.
The hypoglycemic effects are potentially dangerous to patients with diabetes who are taking glucose-lowering medications. Because propolmannan/KGM attenuates postprandial blood glucose, concomitant use with insulin or oral hypoglycemics may amplify their glucose-lowering effect, potentially causing hypoglycemia.
Negative effects reported include flatulence, abdominal pain, gastrointestinal obstruction, and possible modification of the bioavailability of other medications. Glucomannan should be taken at least 2+ hours apart from oral medications due to binding interference. This concern applies most acutely to drugs with narrow therapeutic indices, though systematic human evidence quantifying the magnitude of such interactions remains limited.
Glucomannan has been linked in case reports to cholestatic hepatitis and occupational asthma. These associations are based on isolated case reports and should not be interpreted as established risks at population level; causality has not been confirmed.
Information regarding use during pregnancy and lactation is lacking. Until more information is obtained, use is not recommended in pregnant or breast-feeding women.
Key unknowns remain: long-term safety beyond a year, pregnancy and lactation data, and high-quality studies on clinically important interactions with warfarin and other narrow therapeutic index drugs. Most human clinical trials have been short-term (weeks to a few months), and the long-term safety profile in humans has not been systematically characterized in controlled trials.
Propolmannan, as a purified form of konjac glucomannan, benefits from the regulatory status granted to KGM by the European Food Safety Authority. In 2010, the EFSA NDA Panel prepared scientific opinions on the substantiation of health claims in relation to glucomannan (konjac mannan) and reduction of body weight, reduction of post-prandial glycaemic responses, and maintenance of normal blood cholesterol concentrations. Two specific health claims are authorized in the EU under Commission Regulation (EU) 432/2012:
KGM is generally regarded as safe (GRAS) as a food additive by the FDA. The flour produced from konjac corms is a permitted food ingredient in Europe under E 425.
In terms of the overall evidence picture: Glucomannan has moderate evidence for cholesterol reduction and constipation relief, contested evidence for weight loss (regulatory approval versus subsequent meta-analytic null findings), and a real choking safety signal. The popular weight-loss claim significantly exceeds the meta-analytic evidence. Current evidence suggests konjac offers promising metabolic and gastrointestinal health benefits, though long-term clinical studies are still needed to confirm optimal dosing, safety, and therapeutic efficacy.
Health conditions that Propolmannan may help support.
Body systems that Propolmannan may help support.
Go back