Related Terms

• Alpha-glucomannan, AM#, Amorphophallus konjac, Chrombalance™, 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-Trim™ (glucomannan and guar gum); Glucosahl™ (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.

Scientific Evidence

Tradition/Theory

The below uses are based on tradition or scientific theories. 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 health care professional.

• 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

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

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 Chrombalance™ 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

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. 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.

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.

Author Information

• 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).

References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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