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.
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This supplement has been used in connection with the following health conditions:
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.
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 grams daily
Glucomannan is a viscous, soluble dietary fiber that has been shown to improve metabolism and reduce LDL-cholesterol and non-HDL-cholesterol levels.
is a viscous, soluble dietary fiber that is derived from konjac root. Clinical trials have shown glucomannan has positive impacts on glucose and lipid metabolism. A meta-analysis of 12 randomized controlled trials including 370 participants found that supplementing with 3 grams of glucomannan daily for three weeks or longer reduced LDL-cholesterol levels by 10% and non-HDL-cholesterol levels by 7%.
3 to 10 grams daily
Taking a glucomannan fiber supplement may improve metabolic syndrome.
Glucomannan, a type of water-soluble dietary fiber from the root of the konjac plant, may reduce risk factors in people with metabolic syndrome. A double-blind trial found that 8–13 grams per day of glucomannan improved cholesterol levels and blood glucose control in people with metabolic syndrome. It is thought to work in part by acting as a prebiotic fiber, enhancing colonies of beneficial gut bacteria that participate in regulating metabolism. Even in patients with type 2 diabetes, 3 grams of glucomannan per day for four weeks improved blood glucose control and lipid metabolism compared to placebo.
Type 2 Diabetes
1 to 10 grams daily
Glucomannan delays stomach emptying, leading to more gradual glucose absorption and lower blood glucose 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 carbohydrate digestion and glucose absorption. Supplementing with glucomannan before eating has been shown reduce the post-meal elevation of blood glucose levels and long-term supplementation is associated with better blood glucose control and improvements in LDL-cholesterol levels in people with type 2 diabetes. Research in animals suggests glucomannan may be helpful in managing diabetes-related kidney dysfunction. Doses between 1 and 10 grams of glucomannan per day have demonstrated efficacy in clinical research.
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 , 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.
Adults: 3 to 4 grams daily; adolescents: 2 to 3 grams daily
Supplementing with glucomannan may promote slight weight loss in overweight adults, but findings are mixed.
Glucomannan is a viscous soluble fiber from konjac root that has demonstrated multiple positive effects on metabolic health, including lowering cholesterol, triglyceride, and blood glucose levels. Studies examining its possible role as a weight loss aid, however, have had mixed results. One placebo-controlled trial in 20 participants with obesity found taking 1 gram of glucomannan three times daily at mealtimes for eight weeks, while making no other changes, led to a weight loss of 5.5 pounds. However, an eight-week placebo-controlled trial in 53 adults with overweight and obesity found 1.33 grams of glucomannan three times daily with meals did not impact weight loss. A meta-analysis of findings from eight randomized controlled trials did not find a significant effect of glucomannan on weight loss in people with overweight and obesity.
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.
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.
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.
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.
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 rise in glucose levels after eating carbohydrates. This could result in reduced need for insulin after meals in people with type 1 diabetes. In addition, glucomannan has positive effects on carbohydrate and fat metabolism, as well as the gut microbiota. These properties could lead to benefits in people with type 1 diabetes, but no research has been done to test this possibility.
How It Works
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.
As glucomannan is not an essential nutrient, no deficiency state exists.
Interactions with Supplements, Foods, & Other Compounds
Interactions with Medicines
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.
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.
Last Review: 05-24-2015
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The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2023.