Glucomannan (Amorphophallus konjac) is a soluble dietary fiber derived from the root of the elephant yam or konjac plant, which is native to Asia. There is scientific data that suggests that glucomannan may promote weight loss. At doses of 2-4 g per day, glucomannan was well-tolerated and resulted in significant weight loss in overweight and obese individuals. This was probably due to its beneficial effects in reducing appetite. Additionally, glucomannan has been shown to improve lipid and lipoprotein levels and glycemic status.
Glucomannan is an ingredient found in some weight loss products such as Lipozene, FiberSlim, Propolene and Tetrazene KGM-90. Increased fiber consumption has long been promoted as supporting weight loss.
How does glucomannan work?
Glucomannan can absorb up to 200 times its weight of water. Because it is a fiber, glucomannan expands in the stomach and absorbs fats. These absorbed fats are eliminated from the body and do not undergo digestion, thus neutralizing their caloric effect. Additionally, glucomannan occupies space in the stomach and thus provides a feeling of fullness. With less food eaten, due to reduced appetite, the body will tap into its fat stores for energy. Glucomannan reportedly alleviates constipation, reduces intestinal flora, lowers blood sugar and cholesterol and may possibly promote weight loss and inhibit cancer.
There is clinical evidence validating glucomannans’ various benefits. There are studies that support glucomannan’s promotion of weight loss (e.g. Int J Obes 1984;8(4):289-93; Med Sci Monit 2005;11(1):5-8). Several studies indicate that glucomannan can lower LDL cholesterol, and blood lipid and sugar levels. (e.g. J Am Coll Nutr 2003;22(1):36-42; Diabetes Care 2000;23(1):9-14; Nutr Metab Cardiovasc Dis 2005;15(3):174-80).
In one clinical study, 2 groups of 25 obese patients underwent low calorie diet therapy for 3 months (with or without a 4 gram/day glucomannan). The glucomannan group exhibited a significant loss of body weight and fat mass compared to the group receiving diet therapy alone. In another study, 20 obese subjects were given 1 gram of glucomannan with 8 ounces of water at 1-hour prior to each meal for 2 months. Subjects were instructed not to change their eating or exercise patterns. Results showed a significant weight loss (5.5 lbs) in the glucomannan group relative to the placebo group.
Glucomannan side effects
Consult with a physician before using this supplement. Patients with diabetes should use glucomannan with extreme caution. Glucomannan use is associated with a reduction in the need for hypoglycemic agents, and the product may result in a loss of glycemic control in diabetic patients.
Glucomannan may bind with and inhibit the absorption of certain nutrients. Glucomannan pills can occasionally get stuck in the esophagus and cause a blockage. Indeed, a clinical study (Clin Toxicol (Phila) 2007;45(1):80-2) found that glucomannan-based supplements can pose a potential hazard for patients with adverse upper gastrointestinal pathology. Do not use glucomannan if you have a disorder of the esophagus as the expanding fiber may act as an obstructing to breathing. Glucomannan-containing tablets have been banned in Australia since May 1985 because these also carry the potential for inducing lower gastrointestinal obstruction. Encapsulated and powder forms remain available.
Frequent bowl movements are a side effect of glucomannan at high doses (3-4 grams daily). Information regarding safety and efficacy in pregnancy and lactation is lacking. The hypoglycemic effects are potentially dangerous to diabetics.
Glucomannan dosage
Glucomannan is not an essential nutrient and no daily requirement (RDA) exists. Clinical studies of glucomannan in diabetes, cholesterol control, and obesity have used daily doses of 2 -13 g. Assess your tolerance to glucomannan by starting with a dose that is 50% of the recommended dose on the product label. Increase the dosage gradually, if you can tolerate this amount. Do not exceed the maximum dosage listed on the product label.
Glucomannan composition
Glucomannan is composed of glucose and mannose combined by beta-1,4 glucosidic linkages. The polysaccharide is easily “denatured” through enzymatic cleavage or treatment with weak alkaline solutions, becoming irreversibly water insoluble.
Glucomannan conclusion
Glucomannan is a soluble fiber that appears to have benefits related to weight loss. Although it is possible to get plenty of fiber by eating appropriate fruits and vegetables, many people fail to do this. Glucomannan can reduce appetite, and the subsequent reduction in calorie intake may result in weight loss.
