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Table of Contents > Herbs & Supplements > Konjac glucomannan Print

Konjac glucomannan

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Also listed as: Glucomannan, Amorphophallus konjac
Related terms
Background
Evidencetable
Tradition
Dosing
Safety
Interactions
Attribution
Bibliography

Related Terms
  • Alpha-glucomannan, AM#, Amorphophallus konjac, ChrombalanceT, conjac, devil's tongue, elephant foot yam, elephant yam, fiber, glucomanna, glucomannan root, GM, KJM, konjac, konjac ceramide, konjac fiber, konjac glucomannan, konjac-mannan, konnyaku, manna, Nature's Way® glucomannan root premium, polyactin A, polysaccharide, snake plant, yam flour.
  • Select combination products: Appe-TrimT (glucomannan and guar gum); GlucosahlT (glucomannan, guar gum, and alginate).
  • Note: Although many different species of plants and yeast contain glucomannan (e.g., Candida utilis), this summary will focus only on the glucomannan derived from the konjac plant (Amorphophallus konjac).

Background
  • Native to Asia, the konjac plant (Amorphophallus konjac) is characterized by its heavy tubers (10 pounds or more in weight) and blotchy, snakeskin-patterned stem. It is most known as a source of glucomannan, a soluble, fermentable, and highly viscous dietary fiber derived from the roots of the plant.
  • The konjac plant has been used as a source of both food and medicine in traditional Asian practices for more than a thousand years. More recently, glucomannan extracts derived from the konjac plant have been used as a dietary supplement or as a source of mannose, a sugar substitute in food products.
  • Given the highly viscous nature of glucomannan fiber, it effectively absorbs water in the digestive tract and decreases the absorption of carbohydrates and cholesterol. As such, since the 1980s, Western medicinal practices have valued glucomannan for its potential to reduce cholesterol levels, constipation, blood sugar, and weight. It has also been explored as a component of artificial skin products, and in the treatment of high blood pressure and hyperthyroidism (overactive thyroid), though additional research in these areas is needed.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Preliminary research suggests that glucomannan improves lipid levels in the body by increasing the elimination of neutral sterols and bile acids in the feces. In particular, glucomannan has been shown to decrease cholesterol by interfering with its transport. Additional research is needed to examine its effects in persons with high cholesterol or those taking lipid-lowering agents.

A


Due to its bulking effect on feces and its increased elimination of bacteria that affect fecal movement, glucomannan has been shown to increase the number of bowel movements. Glucomannan has also been suggested as improving symptoms of abdominal and excretory pain. Further research regarding glucomannan's use, efficacy, and long-term safety is needed in this area.

A


In persons with type 2 diabetes, preliminary research has shown that glucomannan lowers both fasting and postprandial (after eating) blood glucose levels. Additional research is needed to investigate its possible interaction with other blood sugar-lowering agents.

A


Preliminary research suggests that glucomannan, most often in combination with a reduced-calorie diet, increases weight loss by increasing the time to swallow, feelings of fullness, and energy lost via the feces. Further comparative and long-term research in this area is needed.

B


Limited research suggests that glucomannan lowers blood pressure. However, findings in this area vary between studies, and definitive conclusions are lacking. Additional research is needed to investigate its long-term effects and its possible interaction with other blood pressure-lowering agents.

C


According to preliminary research, glucomannan may reduce levels of various thyroid hormones in patients with newly diagnosed hyperthyroidism. Further research is required before conclusions can be drawn.

C


In patients with previous gastric surgery, preliminary research suggests glucomannan may improve reactive low blood sugar. Further research is required before conclusions can be drawn.

C


In children with dumping syndrome (rapid transit of gastrointestinal tract contents), preliminary research suggests that glucomannan may improve glucose tolerance. However, reports of increased side effects warrant additional research in this area before conclusions about its suitability in this population can be made.

C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)


Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

  • Acne, aging, antioxidant, asthma, atopic dermatitis (inflammatory skin disorder), cancer, diverticulitis (inflammation of the intestinal lining), elimination of toxins, food preservative, food uses, immunomodulation (immune effects), irritable bowel syndrome, osteoporosis, wound healing (topical).

Dosing

Adults (18 years and older)

  • General: Common dosing instructions for glucomannan are to take the recommended dose one-half hour to one hour before meals.
  • For cholesterol levels, 1.2-15.1 grams of glucomannan, administered as capsules, tablets, bars, biscuits, and refined konjac meals, has been taken by mouth daily for up to 12 weeks.
  • For constipation, 1.5-4 grams of glucomannan has been taken by mouth daily for up to five weeks.
  • For diabetes, 1.2-13 grams of glucomannan has been taken by mouth daily for up to four weeks. However, konjac food has been taken by mouth for longer periods of 65 days.
  • For high blood pressure, up to 13 grams of glucomannan in biscuit form has been taken by mouth for three weeks. Three grams has also been taken by mouth daily for 12 weeks.
  • For hyperthyroidism (an overactive thyroid), 1.3 grams of glucomannan has been taken by mouth in combination with methimazole and propranolol daily for two months.
  • For hypoglycemia (low blood sugar), a single 2.6-5.2 gram dose of glucomannan has been taken by mouth at breakfast.
  • For obesity or weight loss, 1.24-3 grams of glucomannan has been taken by mouth daily in divided doses for 5-8 weeks. For longer periods of 12 weeks, 3 grams has also been taken by mouth daily. Also, 1,240 milligrams of glucomannan as ChrombalanceT has been taken by mouth daily for five weeks as a divided daily dose of six 56-milligram tablets before each meal and four additional tablets at 3:00 p.m. Most studies administered glucomannan in combination with a reduced-calorie diet.

Children (under 18 years old)

  • For constipation in children two years of age or older, 100 milligrams of glucomannan per kilogram of body weight (up to a daily maximum of five grams) has been taken by mouth and with fluids once or twice daily for up to 12 weeks.
  • For obesity or weight loss, 2-3 grams of glucomannan has been taken by mouth daily for four months (in children aged 5.2-15.8 years), as has one gram twice daily for two months.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

  • Avoid with known allergy or hypersensitivity to Amorphophallus konjac or its constituents. Episodes of respiratory sensitization to konjac glucomannan and konjac allergy-related asthma have been reported.

Side Effects and Warnings

  • Glucomannan may cause general stomach discomfort, immune effects, laxative effects, lowered thyroid hormone levels, flatulence, abdominal pain, respiratory sensitization, bronchial asthma, gastrointestinal obstruction, or reduced absorption of vitamins and sulfonylureas (a type of antidiabetic medicine) and other drugs taken by mouth. Cases of ocular (eye) injury from Amorphophallus konjac bulbs and acute hepatitis have also been reported.
  • Glucomannan may interfere with blood glucose control. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
  • Glucomannan may cause low blood pressure. Caution is advised in patients taking drugs, herbs, or supplements that lower blood pressure.
  • Use cautiously in patients using sulfonylureas and other agents taken by mouth, immunomodulatory agents, fat-soluble vitamins, and laxatives, due to possible interactions with these compounds.
  • Use cautiously in patients with immune disorders, thyroid disorders, or ileus (intestinal obstruction).
  • Avoid in pregnant and breastfeeding women, due to a lack of available safety information.
  • Avoid with known allergy or hypersensitivity to Amorphophallus konjac or any of its constituents.
  • Note: Due to the potential of increased dietary fiber to interfere with the availability of other agents, separating the consumption of fiber supplements such as glucomannan from other foods, medications, herbal products, or dietary supplements by two hours is recommended.
  • Note: Use of glucomannan tablets has resulted in esophageal obstruction in one case. Konjac candy has caused choking.

Pregnancy and Breastfeeding

  • Avoid in pregnant and breastfeeding women, due to a lack of available safety information.

Interactions

Interactions with Drugs

  • Glucomannan may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking insulin or drugs for diabetes by mouth should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
  • Glucomannan may cause low blood pressure. Caution is advised in patients taking drugs that lower blood pressure.
  • Glucomannan may interact with antibiotics (such as rifaximin), anticancer agents, antiobesity agents, cholesterol- and lipid-lowering agents, drugs that weaken the immune system (such as cyclophosphamide), glibenclamide, lactulose, laxatives, and thyroid hormones.
  • Note: Due to the potential of increased dietary fiber to interfere with the availability of other agents, separating the consumption of fiber supplements such as glucomannan from other foods, medications, herbal products, or dietary supplements by two hours is recommended.

Interactions with Herbs and Dietary Supplements

  • Glucomannan may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.
  • Glucomannan may cause low blood pressure. Caution is advised in patients taking herbs or supplements that lower blood pressure.
  • Glucomannan may interact with American ginseng, antibacterials, anticancer agents, antiobesity agents, cholesterol- and lipid lowering agents, dietary fiber, fat-soluble vitamins, immunomodulators, laxatives, plant sterols, or thyroid agents.
  • Note: Due to the potential of increased dietary fiber to interfere with the availability of other agents, separating the consumption of fiber supplements such as glucomannan from other foods, medications, herbal products, or dietary supplements by two hours is recommended.

Attribution
  • This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography
  1. Arvill A, Bodin L. Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men. Am J Clin Nutr 1995;61(3):585-589.
  2. Azezli AD, Bayraktaroglu T, Orhan Y. The use of konjac glucomannan to lower serum thyroid hormones in hyperthyroidism. J Am Coll Nutr 2007;26(6):663-668.
  3. Chearskul S, Kriengsinyos W, Kooptiwut S, et al. Immediate and long-term effects of glucomannan on total ghrelin and leptin in type 2 diabetes mellitus. Diabetes Res Clin Pract 2009;83(2):e40-e42.
  4. Chen HL, Cheng HC, Liu YJ, et al. Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults. Nutrition 2006;22(11-12):1112-1119.
  5. Chen HL, Cheng HC, Wu WT, et al. 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.
  6. 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(1):36-42.
  7. Gonzalez CA, Fernandez MN, Sahagun AM, et al. Glucomannan: properties and therapeutic applications. Nutr Hosp 2004;19(1):45-50.
  8. Keithley J, Swanson B. Glucomannan and obesity: a critical review. Altern Ther Health Med 2005;11(6):30-34.
  9. Loening-Baucke V, Miele E, Staiano A. Fiber (glucomannan) is beneficial in the treatment of childhood constipation. Pediatrics 2004;113(3 Pt 1):e259-e264.
  10. Martino F, Martino E, Morrone F, et al. 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.
  11. Salas-Salvado J, Farres X, Luque X, et al. 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.
  12. Sood N, Baker WL, Coleman CI. 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.
  13. Vido L, Facchin P, Antonello I, et al. Childhood obesity treatment: double blinded trial on dietary fibres (glucomannan) versus placebo. Padiatr Padol 1993;28(5):133-136.
  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(6):913-919.
  15. 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(1):9-14.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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