Updated: August 2, 2019
Glucomannan is a dietary fiber. It is usually made from the root of the konjac plant or elephant yam. Glucommanan is available in powder, capsules, and tablets forms that can be used as medicine.
Orally, glucomannan is used for constipation, weight loss, diabetes, high cholesterol, hyperthyroidism or overactive thyroid, high blood pressure, and stomach conditions called dumping syndrome and functional gastrointestinal disorder. In foods, glucomannan is used as a thickener or gelling agent. Glucommanan flour and powder are used in food. Products containing glucomannan, under a variety of brand names, are marketed as dietary supplements with claims they can relieve constipation and help lower cholesterol levels. Glucomannans are also used to supplement animal feed for farmed animals, to help the animals gain weight more quickly.
Glucomannan works in the stomach and intestine by absorbing water to form a bulky fiber which treats constipation. It also slow the absorption of sugar and cholesterol from the gut, thus helping to control sugar levels in diabetes, and reducing cholesterol levels.
Glucomannan has an exceptional ability to absorb water and is one of the most viscous dietary fibers known. Glucomannan comprises 40% by dry weight of the roots, or corm, of the konjac plant or elephant yam. Another culinary source is salep, ground from the roots of certain orchids and used in Turkish cuisine. Glucomannan is also a hemicellulose that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledons. Glucomannan is also a constituent of bacterial, plant and yeast cell wall with differences in the branches or glycosidic linkages in the linear structure. It is used in herbal mixtures and traditional foods like tofu, noodles and konjac jelly. It is also added to food products, such as pasta and flour.
Taking glucomannan by mouth can relieve constipation in adults. It might also reduce constipation in children, but results are inconsistent.
Taking glucomannan by mouth seems to reduce cholesterol, blood sugar levels, and blood pressure in people with diabetes.
Taking glucomannan by mouth seems to improve cholesterol levels in people with high cholesterol.
Dumping syndrome is a stomach condition that 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. Taking glucomannan by mouth helps prevent blood sugar from becoming too low after eating in people at risk for this condition.
Taking glucomannan does not improve stomach pain, cramping, or bloating in children with this condition.
Glucomannan might improve blood pressure in people with high blood pressure.
Hyperthyroidism or Overactive thyroid:
Glucomannan plus methimazole and propranolol reduce thyroid hormone levels in people with too much thyroid hormone in the body.
Taking glucomannan by mouth improves weight loss in overweight and obese adults and children. Like other soluble fibers, glucomannan absorbs water in your stomach and contributes to feelings of fullness. In addition, it may promote reduced calorie intake and weight loss in other ways.
More evidence is needed to rate glucomannan for the uses in other conditions.
Glucomannan powder or flour is likely safe when consumed as food. Glucomannan powder and capsules are possibly for most adults and children when used in medicinal amounts for up to 4 months. However, solid tablets containing glucomannan are possibly unsafe for adults and likely unsafe for children. These can sometimes cause blockages of the throat or intestines.
Supplements containing glucomannans pose a risk for choking and bowel obstruction if they are not taken with sufficient water. Other adverse effects include diarrhea, belching, and bloating. Higher triglyceride levels could also be a possible side effect.
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.
Glucomannan may interfere with blood sugar control. Monitor blood sugar closely if you have diabetes and use glucomannan.
Glucomannan might interfere with blood sugar control during and after surgery. Stop using glucomannan at least 2 weeks before a scheduled surgery.
Be cautious with the below combination as these can have moderate interaction:
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), rosiglitazone (Avandia), chlorpropamide (Diabinese), insulin, pioglitazone (Actos), glipizide (Glucotrol), tolbutamide (Orinase), and others.
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 and is recommended:
Glucomannan doses typically range from 2-4.5 grams daily, taken in divided doses.
Various glucomannan doses and dosage forms have been used, short-term (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.
Doses of about 3-4 grams of glucomannan have been used daily 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.
100 mg/kg of glucomannan has been taken once or twice daily (up to a maximum of 5 grams daily) for up to 12 weeks.
Doses of 1 gram of glucomannan have been taken twice daily for 8 weeks in children 6 years of age and under. Dose of 1.5 grams of glucomannan have been taken twice daily for 8 weeks in children older than 6 years of age.
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