Glucomannan: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews

Overview

Glucomannan is a dietary fiber usually made from the root of the konjac plant. It's historically been used as food and medicine in Asian cultures.

Glucomannan might work in the stomach and intestines by absorbing water to form a bulky fiber which treats constipation. It might also slow the absorption of sugar and cholesterol in the gut, helping to control sugar levels in people with diabetes and reduce cholesterol levels.

People commonly use glucomannan for constipation, diabetes, and high cholesterol. It's also used for high blood pressure, obesity, and many other conditions, but there is no good scientific evidence to support most of these uses.

Uses & Effectiveness

Possibly Effective for

Constipation. Taking glucomannan by mouth seems to relieve constipation in adults, but it's not clear if it helps in children.
Diabetes. Taking glucomannan by mouth seems to reduce cholesterol, blood sugar levels, and blood pressure in people with diabetes.
High levels of cholesterol and other fats (lipids) in the blood (hyperlipidemia). Taking glucomannan by mouth seems to improve cholesterol levels in people with or without high cholesterol.

There is interest in using glucomannan for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

Side Effects

When taken by mouth: Glucomannan powder and flour are commonly consumed in foods. Glucomannan powder and capsules are possibly safe when taken with plenty of water for up to 4 months. But taking glucomannan products without water, especially as tablets, is possibly unsafe. These products might cause choking and other serious side effects when taken without water.

Special Precautions and Warnings

Pregnancy and breast-feeding: There isn't enough reliable information to know if glucomannan is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Glucomannan powder and capsules are possibly safe for most children when taken with plenty of water for up to 4 months. But taking glucomannan products without water, especially as tablets, is likely unsafe. These products might cause choking and other serious side effects when taken without water.

Interactions

Moderate Interaction

Be cautious with this combination

Medications taken by mouth (Oral drugs) interacts with Glucomannan
Taking glucomannan along with medications taken by mouth can decrease how much medicine the body absorbs. To prevent this interaction, take glucomannan at least one hour after medications you take by mouth.

Dosing

In foods, glucomannan powder or flour is commonly used as a thickening agent and as a source of dietary fiber.

As medicine, glucomannan has most often been used by adults in doses of 3-4 grams by mouth daily for up to 3 months. In children, glucomannan has most often been used in doses of 2-5 grams by mouth daily for up to 4 months. Speak with a healthcare provider to find out what dose might be best for a specific condition.

View References

REFERENCES:

Monographs on the medicinal uses of plant drugs. Exeter, UK: European Scientific Co-op Phytother, 1997.

Newall CA, Anderson LA, Philpson JD. Herbal Medicine: A Guide for Healthcare Professionals. London, UK: The Pharmaceutical Press, 1996.

Arvill A, Bodin L. Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men. Am J Clin Nutr 1995;61:585-9.

Vido L, Facchin P, Antonello I, et al. Childhood obesity treatment: double blinded trial on dietary fibres (glucomannan) versus placebo. Padiatr Padol 1993;28:133-6.

Livieri C, Novazi F, Lorini R. [The use of highly purified glucomannan-based fibers in childhood obesity]. Pediatr Med Chir 1992;14:195-8.

Vita PM, Restelli A, Caspani P, et al. [Chronic use of glucomannan in the dietary treatment of severe obesity]. Minerva Med 1992;83:135-9.

Walsh DE, Yaghoubian V, Behforooz A. Effect of glucomannan on obese patients: a clinical study. Int J Obes 1984;8:289-93.

Cairella M, Marchini GAD. [Evaluation of the action of glucomannan on metabolic parameters and on the sensation of satiation in overweight and obese patients]. [Article in Italian] Clin Ter 1995;146:269-74.

Gallaher DD, Gallaher CM, Mahrt GJ, et al. A glucomannan and chitosan fiber supplement decreases plasma cholesterol and increases cholesterol excretion in overweight normocholesterolemic humans. J Am Coll Nutr 2002;21:428-33.

Henry DA, Mitchell AS, Aylward J, et al. Glucomannan and risk of oesophageal obstruction. Br Med J 1986;292:591-2.

Passaretti S, Franzoni M, Comin U, et al. Action of glucomannans on complaints in patients affected with chronic constipation: a multicentric clinical evaluation. Ital J Gastroenterol 1991;23:421-5.

Staiano A, Simeone D, Del Giudice E, et al. Effect of the dietary fiber glucomannan on chronic constipation in neurologically impaired children. J Pediatr 2000;136:41-5.

Chen HL, Sheu WH, Tai TS, et al. Konjac supplement alleviated hypercholesterolemia and hyperglycemia in type 2 diabetic subjects--a randomized double-blind trial. J Am Coll Nutr 2003;22:36-42.

Vuksan V, Sievenpiper JL, Owen R, et al. Beneficial effects of viscous dietary fiber from Konjac-mannan in subjects with the insulin resistance syndrome: results of a controlled metabolic trial. Diabetes Care 2000;23:9-14.

Vuksan V, Jenkins DJ, Spadafora P, et al. Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial. Diabetes Care 1999;22:913-9.

Shima K, Tanaka A, Ikegami H, et al. Effect of dietary fiber, glucomannan, on absorption of sulfonylurea in man. Horm Metab Res 1983;15:1-3.

Doi K, Matsuura M, Kawara A, Baba S. Treatment of diabetes with glucomannan (konjac mannan). Lancet 1979;1:987-8.

Doi K, Matsuura M, Kawara A, et al. Influence of dietary fiber (konjac mannan) on absorption of vitamin B12 and vitamin E (abstract). Tohoku J Exp Med 1983;141:677-81.

Pittler, M. H. and Ernst, E. Dietary supplements for body-weight reduction: a systematic review. Am.J.Clin Nutr. 2004;79(4):529-536.

Birketvedt, G. S., Shimshi, M., Erling, T., and Florholmen, J. Experiences with three different fiber supplements in weight reduction. Med Sci Monit. 2005;11(1):I5-I8.

Nakajima, N., Ishihara, K., and Matsuura, Y. Dietary-fiber-degrading enzymes from a human intestinal Clostridium and their application to oligosaccharide production from nonstarchy polysaccharides using immobilized cells. Appl.Microbiol.Biotechnol. 2002;59(2-3):182-189.

Gonzalez, Canga A., Fernandez, Martinez N., Sahagun, A. M., Garcia Vieitez, J. J., Diez Liebana, M. J., Calle Pardo, A. P., Castro Robles, L. J., and Sierra, Vega M. [Glucomannan: properties and therapeutic applications]. Nutr.Hosp. 2004;19(1):45-50.

Loening-Baucke, V., Miele, E., and Staiano, A. Fiber (glucomannan) is beneficial in the treatment of childhood constipation. Pediatrics 2004;113(3 Pt 1):e259-e264.

McCarty, M. F. Nutraceutical resources for diabetes prevention--an update. Med Hypotheses 2005;64(1):151-158.

Villaverde, A. F., Benlloch, S., Berenguer, M., Miguel, Rayon J., Pina, R., and Berenguer, J. Acute hepatitis of cholestatic type possibly associated with the use of glucomannan (amorphophalus konjac). J Hepatol. 2004;41(6):1061-1062.

Onishi, N., Kawamoto, S., Nishimura, M., Nakano, T., Aki, T., Shigeta, S., Shimizu, H., Hashimoto, K., and Ono, K. The ability of konjac-glucomannan to suppress spontaneously occurring dermatitis in NC/Nga mice depends upon the particle size. Biofactors 2004;21(1-4):163-166.

Martino, F., Martino, E., Morrone, F., Carnevali, E., Forcone, R., and Niglio, T. Effect of dietary supplementation with glucomannan on plasma total cholesterol and low density lipoprotein cholesterol in hypercholesterolemic children. Nutr.Metab Cardiovasc.Dis. 2005;15(3):174-180.

Keithley, J. and Swanson, B. Glucomannan and obesity: a critical review. Altern.Ther.Health Med 2005;11(6):30-34.

Yoshida, M., Vanstone, C. A., Parsons, W. D., Zawistowski, J., and Jones, P. J. Effect of plant sterols and glucomannan on lipids in individuals with and without type II diabetes. Eur.J Clin Nutr. 2006;60(4):529-537.

Chen, H. L., Cheng, H. C., Liu, Y. J., Liu, S. Y., and Wu, W. T. Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults. Nutrition 2006;22(11-12):1112-1119.

Wood, R. J., Fernandez, M. L., Sharman, M. J., Silvestre, R., Greene, C. M., Zern, T. L., Shrestha, S., Judelson, D. A., Gomez, A. L., Kraemer, W. J., and Volek, J. S. Effects of a carbohydrate-restricted diet with and without supplemental soluble fiber on plasma low-density lipoprotein cholesterol and other clinical markers of cardiovascular risk. Metabolism 2007;56(1):58-67.

Vanderbeek, P. B., Fasano, C., O'Malley, G., and Hornstein, J. Esophageal obstruction from a hygroscopic pharmacobezoar containing glucomannan. Clin Toxicol.(Phila) 2007;45(1):80-82.

Kraemer, W. J., Vingren, J. L., Silvestre, R., Spiering, B. A., Hatfield, D. L., Ho, J. Y., Fragala, M. S., Maresh, C. M., and Volek, J. S. Effect of adding exercise to a diet containing glucomannan. Metabolism 2007;56(8):1149-1158.

Onishi, N., Kawamoto, S., Suzuki, H., Hide, M., and Ono, K. Development of autoantibody responses in NC/Nga mice: its prevention by pulverized konjac glucomannan feeding. Arch.Dermatol.Res 2008;300(2):95-99.

Bernstein, J. A., Crandall, M. S., and Floyd, R. Respiratory sensitization of a food manufacturing worker to konjac glucomannan. J Asthma 2007;44(8):675-680.

Salas-Salvado, J., Farres, X., Luque, X., Narejos, S., Borrell, M., Basora, J., Anguera, A., Torres, F., Bullo, M., and Balanza, R. Effect of two doses of a mixture of soluble fibres on body weight and metabolic variables in overweight or obese patients: a randomised trial. Br.J Nutr. 2008;99(6):1380-1387.

Chearskul, S., Sangurai, S., Nitiyanant, W., Kriengsinyos, W., Kooptiwut, S., and Harindhanavudhi, T. Glycemic and lipid responses to glucomannan in Thais with type 2 diabetes mellitus. J Med Assoc.Thai. 2007;90(10):2150-2157.

Ruszova, E., Pavek, S., Hajkova, V., Jandova, S., Velebny, V., Papezikova, I., and Kubala, L. Photoprotective effects of glucomannan isolated from Candida utilis. Carbohydr.Res 2-25-2008;343(3):501-511.

Azezli, A. D., Bayraktaroglu, T., and Orhan, Y. The use of konjac glucomannan to lower serum thyroid hormones in hyperthyroidism. J Am.Coll.Nutr. 2007;26(6):663-668.

Tapola, N. S., Lyyra, M. L., Kolehmainen, R. M., Sarkkinen, E. S., and Schauss, A. G. Safety aspects and cholesterol-lowering efficacy of chitosan tablets. J Am.Coll.Nutr. 2008;27(1):22-30.

Chen, H. L., Cheng, H. C., Wu, W. T., Liu, Y. J., and Liu, S. Y. Supplementation of konjac glucomannan into a low-fiber Chinese diet promoted bowel movement and improved colonic ecology in constipated adults: a placebo-controlled, diet-controlled trial. J Am.Coll.Nutr. 2008;27(1):102-108.

Vasques, C. A., Rossetto, S., Halmenschlager, G., Linden, R., Heckler, E., Fernandez, M. S., and Alonso, J. L. Evaluation of the pharmacotherapeutic efficacy of Garcinia cambogia plus Amorphophallus konjac for the treatment of obesity. Phytother.Res 2008;22(9):1135-1140.

Sood, N., Baker, W. L., and Coleman, C. I. Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis. Am.J Clin Nutr. 2008;88(4):1167-1175.

Huang, C. Y., Zhang, M. Y., Peng, S. S., Hong, J. R., Wang, X., Jiang, H. J., Zhang, F. L., Bai, Y. X., Liang, J. Z., Yu, Y. R., and . Effect of Konjac food on blood glucose level in patients with diabetes. Biomed.Environ.Sci 1990;3(2):123-131.

Zhang, M. Y., Huang, C. Y., Wang, X., Hong, J. R., and Peng, S. S. The effect of foods containing refined Konjac meal on human lipid metabolism. Biomed.Environ.Sci 1990;3(1):99-105.

Cesa, F., Mariani, S., Fava, A., Rauseo, R., and Zanetti, H. [The use of vegetable fibers in the treatment of pregnancy diabetes and/or excessive wight gain during pregnancy]. Minerva Ginecol. 1990;42(6):271-274.

Marzio, L., Del, Bianco R., Donne, M. D., Pieramico, O., and Cuccurullo, F. Mouth-to-cecum transit time in patients affected by chronic constipation: effect of glucomannan. Am.J Gastroenterol. 1989;84(8):888-891.

Kawamura, Y. and Horio, T. [Effects of chewing exercise on the maximum biting force and chewing performance]. Shika.Kiso.Igakkai Zasshi 1989;31(3):281-290.

Kneepkens, C. M., Fernandes, J., and Vonk, R. J. Dumping syndrome in children. Diagnosis and effect of glucomannan on glucose tolerance and absorption. Acta Paediatr.Scand. 1988;77(2):279-286.

Hopman, W. P., Houben, P. G., Speth, P. A., and Lamers, C. B. Glucomannan prevents postprandial hypoglycaemia in patients with previous gastric surgery. Gut 1988;29(7):930-934.

Fanelli, V., Angelico, F., Stefanutti, C., Calvieri, A., and Fazio, S. [Effects of the integration of a habitual diet with glucomannan fiber in hypercholesterolemia. A clinical study in familial and sporadic hyperlipoproteinemia with lipo-proteic phenotype IIa and IIb]. Clin Ter. 10-15-1986;119(1):17-23.

Scalfi, L., Coltorti, A., D'Arrigo, E., Carandente, V., Mazzacano, C., Di, Palo M., and Contaldo, F. Effect of dietary fibre on postprandial thermogenesis. Int.J Obes. 1987;11 Suppl 1:95-99.

Shichijo, K., Kobayashi, Y., Fueki, R., Shimoyama, K., and Masaya, M. [2 cases of konjac bronchial asthma found outside the "konnyaku" producing district]. Arerugi 1969;18(2):97-100.

Rosado, J. L. and Diaz, M. [Physico-chemical properties related to gastrointestinal function of 6 sources of dietary fiber]. Rev.Invest Clin 1995;47(4):283-289.

Marsicano, L. J., Berrizbeitia, M. L., and Mondelo, A. [Use of glucomannan dietary fiber in changes in intestinal habit]. G.E.N. 1995;49(1):7-14.

Doi, K., Matsuura, M., Kawara, A., and Baba, S. Treatment of diabetes with glucomannan (konjac mannan). Lancet 5-5-1979;1(8123):987-988.

Signorelli, P., Croce, P., and Dede, A. [A clinical study of the use of a combination of glucomannan with lactulose in the constipation of pregnancy]. Minerva Ginecol. 1996;48(12):577-582.

Nakajima, N. and Matsuura, Y. Purification and characterization of konjac glucomannan degrading enzyme from anaerobic human intestinal bacterium, Clostridium butyricum-Clostridium beijerinckii group. Biosci.Biotechnol.Biochem. 1997;61(10):1739-1742.

Matsuura, Y. Degradation of konjac glucomannan by enzymes in human feces and formation of short-chain fatty acids by intestinal anaerobic bacteria. J Nutr.Sci Vitaminol.(Tokyo) 1998;44(3):423-436.

Venter, C. S., Kruger, H. S., Vorster, H. H., Serfontein, W. J., Ubbink, J. B., and De Villiers, L. S. The effects of the dietary fibre component konjac-glucomannan on serum cholesterol levels of hypercholesterolemic subjects. Hum Nut:Food Serv Nutr 1987;41F:55-61.

Brand-Miller JC, Atkinson FS, Gahler RJ, et al. Effects of PGX, a novel functional fibre, on acute and delayed postprandial glycaemia. Eur J Clin Nutr 2010;64(12):1488-93.

Brand-Miller JC, Atkinson FS, Gahler RJ, et al. Effects of added PGX, a novel functional fibre, on the glycaemic index of starchy foods. Br J Nutr 2012;108(2):245-8.

Carabin IG, Lyon MR, Wood S, et al. Supplementation of the diet with the functional fiber PolyGlycoplex is well tolerated by healthy subjects in a clinical trial. Nutr J 2009;8:9.

Chmielewska A, Horvath A, Dziechciarz P, Szajewska H. Glucomannan is not effective for the treatment of functional constipation in children: a double-blind, placebo-controlled, randomized trial. Clin Nutr 2011;30(4):462-8.

Horvath A, Dziechciarz P, Szajewska H. Glucomannan for abdominal pain-related functional gastrointestinal disorders in children: a randomized trial. World J Gastroenterol 2013;19(20):3062-8.

Jenkins AL, Kacinik V, Lyon MR, Wolever TM. Reduction of postprandial glycemia by the novel viscous polysaccharide PGX, in a dose-dependent manner, independent of food form. J Am Coll Nutr 2010;29(2):92-8.

Kaats GR, Bagchi D, Preuss HG. Konjac glucomannan dietary supplementation causes significant fat loss in compliant overweight adults. J Am Coll Nutr 2015; Online ahead of print.

Keithley JK, Swanson B, Mikolaitis SL, et al. Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults. J Obes 2013;2013:610908.

Lyon MR, Reichert RG. The effect of a novel viscous polysaccharide along with lifestyle changes on short-term weight loss and associated risk factors in overweight and obese adults: an observational retrospective clinical program analysis. Altern Med Rev 2010;15(1):68-75.

Lyon M, Wood S, Pelletier X, et al. Effects of a 3-month supplementation with a novel soluble highly viscous polysaccharide on anthropometry and blood lipids in nondieting overweight or obese adults. J Hum Nutr Diet 2011;24(4):351-9.

Onakpoya I, Posadzki P, Ernst E. The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trial. J Am Coll Nutr 2014;33(1):70-8.

Han Y, Zhang L, Liu XQ, Zhao ZJ, Lv LX. Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials. Asia Pac J Clin Nutr 2017;26(3):471-7.

Ho HVT, Jovanovski E, Zurbau A, et al. A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B. Am J Clin Nutr 2017;105(5):1239-47.

Questions and Answers on Dietary Fiber. Available at: https://www.fda.gov/food/food-labeling-nutrition/questions-and-answers-dietary-fiber?utm_campaign=CFSANCU_Citizen_Petition_Glucomannan_Dietary_Fiber&utm_medium=email&utm_source=Eloqua#fda_actions. Accessed January 14, 2020.

Health Canada Safety Alert. Health Canada Advises Canadians that natural health products containing glucomannan may cause serious choking if used with insufficient fluid. January 29, 2010. Alert # RA-110003825. https://healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2010/13439a-eng.php

Mortensen A, Aguilar F, Crebelli, et al. EFSA Panel on Food Additives and Nutrient Sources added to Food. Re-evaluation of konjac gum (E 425 i) and konjac glucomannan (E425 ii) as food additives. EFSA Journal 2017;15(6):4864.

Nagasawa T, Kimura T, Yoshida A, et al. Konjac Glucomannan Attenuated Triglyceride Metabolism during Rice Gruel Tolerance Test. Nutrients 2021;13(7):2191.

Li Y, Kang Y, Du Y, et al. Effects of Konjaku Flour on the Gut Microbiota of Obese Patients. Front Cell Infect Microbiol 2022;12:771748.

Mirzababaei A, Zandkarimi R, Moradi S, et al. The effect of Glucomannan on fasting and postprandial blood glucose in adults: a systematic review and meta-analysis of randomized controlled trials. J Diabetes Metab Disord 2022;21(1):1055-1063.

Fernandes ACS, Muxfeldt L, Motta NG, et al. Gummies candy enriched with Konjac glucomannan reduces hunger intensity and waist circumference of overweight individuals. Int J Biol Macromol 2023;226:72-76.

Jenko Pra&zcaron;nikar Z, Mohorko N, Gmajner D, Kenig S, Petelin A. Effects of Four Different Dietary Fibre Supplements on Weight Loss and Lipid and Glucose Serum Profiles during Energy Restriction in Patients with Traits of Metabolic Syndrome: A Comparative, Randomized, Placebo-Controlled Study. Foods 2023;12(11):2122.

Zhang Z, Zhang Y, Tao X, Wang Y, Rao B, Shi H. Effects of Glucomannan Supplementation on Type II Diabetes Mellitus in Humans: A Meta-Analysis. Nutrients 2023;15(3):601.

Zhang Y, Aldamarany WAS, Song G, et al. Influence of konjac glucomannan and its derivatives on the oral pharmacokinetics of antimicrobial agent in antibiotics cocktails: Keep vigilant on dietary fiber supplement. Int J Biol Macromol 2023;251:126306.

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Glucomannan - Uses, Side Effects, and More