Uses

Glucomannan is a water-soluble dietary fiber that is derived from konjac root (Amorphophallus konjac). Like other forms of dietary fiber, glucomannan is considered a "bulk-forming laxative." Glucomannan promotes a larger, bulkier stool that passes through the colon more easily and requires less pressure-and subsequently less straining-to expel.

Botanical names:
Amorphophallus konjac
What Are Star Ratings?

This supplement has been used in connection with the following health conditions:

Used for Why
3 Stars
Constipation
3 to 4 grams daily in water, followed by a second glass of water
Glucomannan is a water-soluble dietary fiber that has shown to be effective as a bulk-forming laxative.

Glucomannan is a water-soluble dietary fiber that is derived from konjac root. Like other sources of fiber, such as psyllium and fenugreek, glucomannan is considered a bulk-forming laxative. A preliminary trial and several double-blind trials have found glucomannan to be an effective treatment for constipation. The amount of glucomannan shown to be effective as a laxative is 3 to 4 grams per day. In constipated people, glucomannan and other bulk-forming laxatives generally help produce a bowel movement within 12 to 24 hours.

3 Stars
High Cholesterol
4 to 13 grams daily
Glucomannan is a water-soluble dietary fiber that has been shown to significantly reduce total blood cholesterol, LDL cholesterol, and triglycerides, and to raise HDL cholesterol.
Glucomannan is a water-soluble dietary fiber that is derived from konjac root. Controlled and double-blind trials have shown that supplementation with glucomannan significantly reduced total blood cholesterol, LDL cholesterol, and triglycerides, and in some cases raised HDL cholesterol. Effective amounts of glucomannan for lowering blood cholesterol have been 4 to 13 grams per day.
3 Stars
Insulin Resistance Syndrome
8 to 13 grams daily
Taking a glucomannan fiber supplement may improve blood cholesterol and blood sugar.

Glucomannan, a type of water-soluble dietary fiber, may reduce many risk factors in people with IRS. A double-blind trial found that 8-13 grams per day of glucomannan significantly improved several measures of blood cholesterol control and one measure of blood glucose control in people with IRS. Another double-blind study of healthy people found that 30 grams per day of guar gum, a fiber similar to glucomannan, improved insulin sensitivity and many other components of IRS, including blood pressure and blood glucose, cholesterol, and triglycerides, leading the authors to recommend guar gum for people with IRS. However, in another study, obese people taking 8-16 grams per day of guar gum for 6-12 weeks did not experience any change in insulin sensitivity.

3 Stars
Type 2 Diabetes
500 to 700 mg per 100 calories in the diet
Glucomannan delays stomach emptying, leading to more gradual sugar absorption and lower blood sugar levels after meals.
Glucomannan is a water-soluble dietary fiber derived from konjac root (Amorphophallus konjac)that delays stomach emptying, leading to a more gradual absorption of dietary sugar. This effect can reduce the elevation of blood sugar levels that is typical after a meal. After-meal blood sugar levels are lower in people with diabetes given glucomannan in their food, and overall diabetic control is improved with glucomannan-enriched diets, according to preliminary and controlled clinical trials. One preliminary report suggested that glucomannan may also be helpful in pregnancy-related diabetes. For controlling blood sugar, 500 to 700 mg of glucomannan per 100 calories in the diet has been used successfully in controlled research.
2 Stars
Childhood Obesity
2 to 3 grams daily
Glucomannan, a type of fiber, dilutes calories, slows down the eating process, and may make people feel more full despite eating fewer calories.

Increased fiber intake is thought to have potential benefit in a weight-loss program since dietary fiber dilutes calories, slows down the eating process, and may make people feel more full despite eating fewer calories. However, research on using fiber in the treatment of childhood obesity has focused on using fiber supplements rather than comparing low- and high-fiber diets. Supplementation for four months with 2 to 3 grams per day of a bulking agent called glucomannan, was effective in a group of obese adolescents in one controlled trial, but another controlled trial found no significant effect of 2 grams per day for two months.

2 Stars
Obesity
Adults: 3 to 4 grams daily; adolescents: 2 to 3 grams daily
Supplementing with glucomannan, a bulking agent, has promoted weight loss in overweight adults.
Supplementing with 3 to 4 grams per day of a bulking agent called glucomannan, with or without calorie restriction, has promoted weight loss in overweight adults, while 2 to 3 grams per day was effective in a group of obese adolescents in another controlled trial.
1 Star
Diverticular Disease
Refer to label instructions
Glucomannan is a water-soluble dietary fiber. One study found that people with diverticular disease had reduced symptoms after taking glucommanan.

Glucomannan is a water-soluble dietary fiber that is derived from konjac root (Amorphophallus konjac). A preliminary clinical trial found that approximately one-third to one half of people with diverticular disease had reduced symptoms of diverticular disease after taking glucommanan. The amount of glucomannan shown to be effective as a laxative is 3-4 grams per day.

1 Star
Hypoglycemia
Refer to label instructions
Glucomannan is a water-soluble dietary fiber. In one trial, adding glucomannan to a meal prevented hypoglycemia in adults with previous stomach surgery.

Glucomannan is a water-soluble dietary fiber that is derived from konjac root (Amorphophallus konjac). In a preliminary trial, addition of either 2.6 or 5.2 grams of glucomannan to a meal prevented hypoglycemia in adults with previous stomach surgery. A trial of glucomannan in children with hypoglycemia due to a condition known as "dumping syndrome" produced inconsistent results.

1 Star
Type 1 Diabetes
Refer to label instructions
Glucomannan delays stomach emptying, leading to more gradual sugar absorption and possibly lowering insulin requirements for people with type 1 diabetes.
Glucomannan is a water-soluble dietary fiber derived from konjac root (Amorphophallus konjac). Glucomannan delays stomach emptying, leading to a more gradual absorption of dietary sugar. This effect can reduce the elevation of blood sugar levels that is typical after a meal. This could lower insulin requirements for type 1 diabetics, but no research has been done to test this possibility.

How It Works

Botanical names:
Amorphophallus konjac

How to Use It

The amount of glucomannan shown to be effective as a laxative is 3-4 grams per day.1 , 2 Effective amounts for lowering blood cholesterol have been 4-13 grams per day.3 , 4 , 5 For controlling blood sugar, 500-700 mg of glucomannan per 100 calories in the diet has been used successfully in controlled research.6 , 7 For weight loss, 1 to 3 grams before each meal has been effective.8 , 9 When using glucomannan and other dietary fiber supplements, it is best to start out with a small amount and increase gradually. It is recommended to drink at least 8 ounces of water each time any bulk-forming laxative, including glucomannan, is taken.

Where to Find It

Glucomannan is a purified fiber from konjac root that is available as a bulk powder to be taken in hard-gelatin capsules or used as an ingredient in food.

Possible Deficiencies

As glucomannan is not an essential nutrient, no deficiency state exists.

Interactions

Botanical names:
Amorphophallus konjac

Interactions with Supplements, Foods, & Other Compounds

At the time of writing, there were no well-known supplement or food interactions with this supplement.

Interactions with Medicines

As of the last update, we found no reported interactions between this supplement and medicines. It is possible that unknown interactions exist. If you take medication, always discuss the potential risks and benefits of adding a new supplement with your doctor or pharmacist.
The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers' package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Botanical names:
Amorphophallus konjac

Side Effects

People with any disorder of the esophagus (the tube leading from the mouth to the stomach) should not take any fiber supplement in a pill form, as the supplement may expand in the esophagus and lead to obstruction.10 Preliminary reports in humans, as well and animal research, suggest that some people may be sensitive to inhaled glucomannan powder.11

Since intestinal bacteria ferment water-soluble fibers, a great deal of intestinal gas may be produced in individuals not accustomed to a high fiber diet, leading to flatulence and abdominal discomfort.

References

1. Marsicano LJ, Berrizbeitia ML, Mondelo A. Use of glucomannan dietary fiber in changes in intestinal habit. G E N 1995;49:7-14 [in Spanish].

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.

3. 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.

4. 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.

5. 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.

6. 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.

7. 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.

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

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

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

11. Werley MS, Burleigh-Flayer H, Mount EA, Kotkoskie LA. Respiratory sensitization to konjac flour in guinea pigs. Toxicology 1997;124:115-24.