Glucomannan

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Glucomannan is a water-soluble polysaccharide that is considered a dietary fiber. Glucomannan is a food additive used as an emulsifier and thickener. Products containing glucomanan, marketed under a variety of brand names, are also sold as nutritional supplements for constipation, obesity, high cholesterol, acne vulgaris and type 2 diabetes. Though there is some clinical support for potential health benefits, the U.S. Food and Drug Administration (FDA) has not approved any product containing glucomannan for the treatment of these medical conditions. Several companies selling products containing glucomanna have been disciplined by the U.S. Federal Trade Commission (FTC) for misleading or exaggerated claims pertaining to the health benefits of glucomannan supplements.

Contents

[edit] Chemistry

Glucomannan is mainly a straight-chain polymer, with a small amount of branching. The component sugars are β-(1→4)-linked D-mannose and D-glucose in a ratio of 1.6:1.[1] The degree of branching is about 8% through β-(1→6)-glucosyl linkages.

[edit] Natural sources

Glucomannan comprises 40% by dry weight of the roots or corm of the konjac plant. It is also a hemicellulose that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledons.

[edit] Potential health benefits

Clinical and pre-clinical studies have shown several potential health benefits of glucomannan.

[edit] Constipation

Glucomannan is a soluble fiber, and as such, has been investigated for the treatment of constipation. Glucomannan may relieve constipation by decreasing fecal transit time.[2] In the treatment of chronic constipation, glucomannan significantly improved symptoms of constipation while being well-tolerated and free of relevant side effects.[3]

[edit] Obesity

Clinical evidence suggests glucomannan may be beneficial in weight loss.[4] Because it is a soluble fiber, it absorbs water to form a viscous gel-like mass. This mass may promote feelings of satiety while traveling through the gastrointestinal tract. In obese patients, taking 1 gram of glucomannan with 8 ounces (250 ml) of water 1 hour before each of 3 meals daily over 8 weeks resulted in an average weight loss of 5.5 pounds (2.5 kg).[5]

[edit] Cholesterol and other lipids

Glucomannan has demonstrated statistically significant improvements in the total cholesterol of obese patients.[5] In healthy men, 4 weeks of taking 3.9 grams of glucomannan decreased total cholesterol, low-density lipoprotein, triglycerides, and systolic blood pressure; notably, triglycerides dropped by 23%.[6] Glucomannan has also been tested in children with high cholesterol in conjunction with a diet. Interestingly, greater decreases in total cholesterol and low-density lipoprotein were observed in female children when compared to male children.[7] When used in conjunction with chitosan, glucomannan decreases serum cholesterol possibly by increasing steroid excretion via the feces.[8]

[edit] Type 2 diabetes

Glucomannan may be useful as a therapeutic adjunct for type 2 diabetes. It has been shown to improve the lipid profile and alleviate the fasting blood glucose levels of type 2 diabetics.[9]

[edit] Commercial use

As a food additive, glucomannan is used as an emulsifier and thickener. It has E number E425(ii). Glucomannan also makes up the majority of shirataki noodles.

[edit] Dietary supplements

Glucomannan is an ingredient in a variety of dietary supplement products marketed via television advertisements claiming to aid in weight loss. According to the FTC, there is no clinical data supporting many of the claims[10][11] and several companies have been determined by the FTC or the FDA to have violated the Federal Food, Drug, and Cosmetic Act including Vitacost,[12] PediaLean,[13] Herbal Worldwide Holdings,[14] BioTrim,[15] and others. The company Obesity Research Institute, the marketer of FiberThin, Propolene and Lipozene, settled FTC charges that their misleading weight-loss claims violated federal laws by agreeing to pay $1.5 million in consumer redress.[16]

In 2002, a number of products containing kojac-derived glucomannan were recalled as choking hazards.[17]

[edit] References

  1. ^ Kaname Katsuraya, Kohsaku Okuyamab, Kenichi Hatanakab, Ryuichi Oshimab, Takaya Satoc, and Kei Matsuzakic (2003). "Constitution of konjac glucomannan: chemical analysis and 13C NMR spectroscopy". Carbohydrate Polymers 53 (2): 183-189. doi:10.1016/S0144-8617(03)00039-0. 
  2. ^ Marzio L, Del Bianco R, Donne MD, Pieramico O, Cuccurullo F (August 1989). "Mouth-to-cecum transit time in patients affected by chronic constipation: effect of glucomannan". Am. J. Gastroenterol. 84 (8): 888–91. PMID 2547312. 
  3. ^ Passaretti S, Franzoni M, Comin U, et al (1991). "Action of glucomannans on complaints in patients affected with chronic constipation: a multicentric clinical evaluation". Ital J Gastroenterol 23 (7): 421–5. PMID 1742540. 
  4. ^ Keithley J, Swanson B (2005). "Glucomannan and obesity: a critical review". Altern Ther Health Med 11 (6): 30–4. PMID 16320857. 
  5. ^ a b Walsh DE, Yaghoubian V, Behforooz A (1984). "Effect of glucomannan on obese patients: a clinical study". Int J Obes 8 (4): 289–93. PMID 6096282. 
  6. ^ Arvill A, Bodin L (March 1995). "Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men". Am. J. Clin. Nutr. 61 (3): 585–9. PMID 7872224. 
  7. ^ Martino F, Martino E, Morrone F, Carnevali E, Forcone R, Niglio T (June 2005). "Effect of dietary supplementation with glucomannan on plasma total cholesterol and low density lipoprotein cholesterol in hypercholesterolemic children". Nutr Metab Cardiovasc Dis 15 (3): 174–80. doi:10.1016/j.numecd.2004.04.004. PMID 15955465. 
  8. ^ Gallaher DD, Gallaher CM, Mahrt GJ, et al (October 2002). "A glucomannan and chitosan fiber supplement decreases plasma cholesterol and increases cholesterol excretion in overweight normocholesterolemic humans". J Am Coll Nutr 21 (5): 428–33. PMID 12356785. 
  9. ^ Chen HL, Sheu WH, Tai TS, Liaw YP, Chen YC (February 2003). "Konjac supplement alleviated hypercholesterolemia and hyperglycemia in type 2 diabetic subjects--a randomized double-blind trial". J Am Coll Nutr 22 (1): 36–42. PMID 12569112. 
  10. ^ Ads for Various Diet Supplements and Topical Gels Don’t Cut the Fat, Says the FTC, Federal Trade Commission
  11. ^ What are some of the questionable weight loss products?, United States Food and Drug Administration
  12. ^ Food and Drug Administration letter
  13. ^ Federal Trade Commission complaint
  14. ^ Federal Trade Commission complaint
  15. ^ Federal Trade Commission letter
  16. ^ FTC Settles Claims with Marketers of FiberThin and Propolene, Federal Trade Commission
  17. ^ U.S. FDA Konjac Candy Recalls - U.S. FDA konjac or glucomannan containing candy concerns and recalls

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