Glucomanano, Glucomannane, Konjac Mannan.


Overview Information

Glucomannan is a dietary fiber. It is usually made from the root of the konjac plant. Glucommanan powder, capsules, and tablets are used as medicine.

Glucomannan is used for constipation, diabetes, and high cholesterol. Some people take glucomannan by mouth for high blood pressure, obesity, and other conditions, but there is no good scientific evidence to support these other uses of glucomannan.

In foods, glucomannan is used as a thickener or gelling agent. It is also included in food as a dietary fiber.

How does it work?

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


Uses & Effectiveness?

Possibly Effective for

  • Constipation. Taking glucomannan by mouth can relieve constipation in adults. It might also reduce constipation in children, but results are mixed.
  • Diabetes. Taking glucomannan by mouth seems to reduce cholesterol, blood sugar levels, and blood pressure in people with diabetes.
  • High cholesterol. Taking glucomannan by mouth seems to improve cholesterol levels in people with or without high cholesterol.

Insufficient Evidence for

  • Rapid gastric emptying (dumping syndrome). Dumping syndrome occurs when food moves from the stomach to the intestines too quickly. This can cause the body to release a large amount of insulin, which can cause low blood sugar. Some early research shows that taking glucomannan by mouth helps prevent blood sugar from becoming too low after eating in people at risk for this condition. However, not all research agrees.
  • High blood pressure. Early research shows that glucomannan might improve blood pressure in people with high blood pressure.
  • Overactive thyroid (hyperthyroidism). Early research shows that adding glucomannan to treatment with methimazole and propranolol helps to reduce thyroid hormone levels in people with overactive thyroid.
  • Obesity. Some early research shows that taking glucomannan by mouth improves weight loss in overweight and obese adults and children. However, not all research agrees.
  • Disorders marked by persistent and recurring GI symptoms (functional gastrointestinal disorders).
  • Other conditions.
More evidence is needed to rate glucomannan for these uses.

Side Effects

Side Effects & Safety

When taken by mouth: Glucomannan powder or flour is LIKELY SAFE for most adults when consumed as food. Glucomannan powder and capsules are POSSIBLY SAFE when used as medicine, short-term. But solid tablets containing glucomannan are POSSIBLY UNSAFE for adults. These tablets may cause blockages of the throat or intestines.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking glucomannan if you are pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Glucomannan powder and capsules are POSSIBLY SAFE for most children when used as medicine, short-term. But solid tablets containing glucomannan are LIKELY UNSAFE. These tablets may cause blockages of the throat or intestines.



Moderate Interaction

Be cautious with this combination

  • Medications for diabetes (Antidiabetes drugs) interacts with GLUCOMANNAN

    Glucomannan can decrease blood sugar in people with type 2 diabetes. Diabetes medications are also used to lower blood sugar. Taking glucomannan along with diabetes medications might cause your blood sugar to go too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.

    Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.

  • Medications taken by mouth (Oral drugs) interacts with GLUCOMANNAN

    Glucomannan absorbs substances in the stomach and intestines. Taking glucomannan along with medications taken by mouth can decrease how much medicine your body absorbs, and decrease the effectiveness of your medication. To prevent this interaction, take glucomannan at least one hour after medications you take by mouth.



The following doses have been studied in scientific research:



  • For constipation: 2-4.5 grams per day, taken in single or split doses, for up to 12 weeks.
  • For high cholesterol: Various glucomannan doses and dosage forms have been used for up to 12 weeks. These include eating biscuits containing 0.5-0.7 grams of glucomannan per 100 kcal, taking 2.4-3.9 grams of glucomannan supplements daily, eating bars containing 3.33 grams of glucomannan three times daily, or eating foods containing 5-10 grams of glucomannan daily.
  • For diabetes: 3-4 grams per day for up to 8 weeks. Eating biscuits containing 0.5-0.7 grams of glucomannan per 100 kcal has also been used for 3 weeks. A specific supplement providing 2.5-7.5 grams of glucomannan has also been used with meals.

  • For constipation: Up to 5 grams in single doses or split doses daily for 4-12 weeks.
  • For high cholesterol: 2-3 grams in single doses or split doses daily for 8 weeks.

View References


  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Pittler, M. H. and Ernst, E. Dietary supplements for body-weight reduction: a systematic review. Am.J.Clin Nutr. 2004;79(4):529-536. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Doi, K., Matsuura, M., Kawara, A., and Baba, S. Treatment of diabetes with glucomannan (konjac mannan). Lancet 5-5-1979;1(8123):987-988. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Keithley, J. and Swanson, B. Glucomannan and obesity: a critical review. Altern.Ther.Health Med 2005;11(6):30-34. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • McCarty, M. F. Nutraceutical resources for diabetes prevention--an update. Med Hypotheses 2005;64(1):151-158. View abstract.
  • Morgan, L. M., Tredger, J. A., Wright, J., and Marks, V. The effect of soluble- and insoluble-fibre supplementation on post-prandial glucose tolerance, insulin and gastric inhibitory polypeptide secretion in healthy subjects. Br.J Nutr. 1990;64(1):103-110. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Henry DA, Mitchell AS, Aylward J, et al. Glucomannan and risk of oesophageal obstruction. Br Med J 1986;292:591-2.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract
  • 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. View abstract.
  • Livieri C, Novazi F, Lorini R. [The use of highly purified glucomannan-based fibers in childhood obesity]. Pediatr Med Chir 1992;14:195-8. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Marone PA, Lyon M, Gahler R, et al. Genotoxicity studies of PolyGlycoleX (PGX): a novel dietary fiber. Int J Toxicol 2009;28(4):318-31. View abstract.
  • Matulka RA, Lyon MR, Wood S, et al. The safety of PolyGlycopleX (PGX) as shown in a 90-day rodent feeding study. Nutr J 2009;8:1. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Questions and Answers on Dietary Fiber. Available at: Accessed January 14, 2020.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • 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. View abstract.
  • Walsh DE, Yaghoubian V, Behforooz A. Effect of glucomannan on obese patients: a clinical study. Int J Obes 1984;8:289-93. View abstract.

Vitamins Survey

Have you ever purchased GLUCOMANNAN?

Did you or will you purchase this product in-store or online?

Where did you or where do you plan to purchase this product?

Where did you or where do you plan to purchase this product?

What factors influenced or will influence your purchase? (check all that apply)

Vitamins Survey

Where did you or where do you plan to purchase this product?

Do you buy vitamins online or instore?

What factors are most important to you? (check all that apply)

This survey is being conducted by the WebMD marketing sciences department.Read More

More Resources for GLUCOMANNAN

CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

This copyrighted material is provided by Natural Medicines Comprehensive Database Consumer Version. Information from this source is evidence-based and objective, and without commercial influence. For professional medical information on natural medicines, see Natural Medicines Comprehensive Database Professional Version.
© Therapeutic Research Faculty .