GLUCOMANNAN
DESCRIPTION Glucomannan is a hydrocolloidal polysaccharide comprised of D-glucose and D-mannose residues (hence, the name) bonded together in beta-1,4 linkages. Approximately 60% of the polysaccharide is made up of D-mannose and approximately 40%, of D-glucose. Some of the sugar residues in glucomannan are acetylated. The molecular weight of this slightly branched polysaccharide ranges from 200 kilodaltons to 2,000 kilodaltons. Glucomannan, which is also classified as a soluble dietary fiber, is derived from konjac flour. Konjac flour itself is derived from the Amorphophallus species, plants which are related to the common philodendron house plant and which grow in only certain parts of the world, including some regions in China and Japan. One member of the Amorphophallus genus called Amorphophallus konjac, is also known as voodoo lilly, devil's tongue and konjac. Konjac flour, however is derived from the tubers of various species of Amorphophallus, and the term konjac is used generically for the various species, as well as for the flour from their tubers. In addition to being known as konjac, the plant is called ju ruo (pronounced in Chinese) by the Chinese people, and called konjaku or konnyaku by the Japanese. Konjac flour has a long history of use in both China and Japan as a food substance and as a folk remedy. Glucomannan products are widely used in Japan and China as general health aids, topically, for skin care and as a thickening agent for foods, among other things. Glucomannan, sometimes called konjac mannan, is marketed in the United States as a dietary supplement. Polysaccharides containing D-mannose and D-glucose in similar proportions to that found in konjac flour are found in other organisms, such as certain yeasts. Yeast glucomannan is not marketed as a dietary supplement. ACTIONS AND PHARMACOLOGY ACTIONS Glucomannan may have laxative activity. It may also have activity in the control of serum glucose and lipid levels. Glucomannan has putative bariatric activity. MECHANISM OF ACTION The laxative effect of glucomannan is thought to be due to the swelling of glucomannan with consequent increase in stool bulk. Some studies indicate that glucomannan may improve glycemic control in Type 2 diabetics. The mechanism of this effect is unclear. Glucomannan may delay the absorption of carbohydrates by increasing gastric-emptying time and/or decreasing small intestinal transit time. The mechanism of glucomannan's possible hypocholesterolemic activity is likewise, unclear. The polysaccharide may stimulate the conversion of cholesterol to bile acids, as well as the fecal excretion of bile acids. Glucomannan may also decrease the intestinal absorption of cholesterol. The putative bariatric (weight reduction) effect of glucomannan is not well understood. The swelling of glucomannan that occurs when it absorbs water in the gastrointestinal tract, may confer a feeling of satiety in some.
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