What is Glucomannan?

Glucomannan: Good for the Gut?

Glucomannan is a polymer of mannose and glucose monomers linked by β-1,4 glycosidic bonds. It is derived from the konjac (Amorphophallus konjac) plant and has been used in foods for centuries in eastern Asia. Glucomannan is used as a food thickener and emulsifier. It is also the major ingredient of konnyaku and shirataki noodles, which have long been dietary staples in Asia but are recently gaining popularity in other countries because of their low-caloric and high-fiber content.

In general, soluble fibers are believed to have beneficial effects on blood lipid profiles, blood sugar profiles, satiety, constipation and immunity. A recent randomized controlled trial found that glucomannan was not effective for treating functional constipation in children. However, the high viscosity and fiber content is believed to aid in weight loss, several studies have shown glucomannan to promote satiety (a feeling of fullness) and weight loss.

As a soluble fiber, glucomannan has a particularly high viscosity (thickness) and capacity to absorb water. The gelatinous material expands more than 200 times in volume, thus inducing satiety.

Furthermore, glucomannan may improve cardiovascular risk factors and blood sugar levels. A 2008 meta-analysis of 14 studies found that glucomannan beneficially affects total cholesterol, low-density lipoprotein (LDL) levels, triglycerides, body weight, and fasting blood glucose. Daily doses of two to four grams (taken with water before or with meals) appear to be well tolerated.

Glucomannan's uniquely high viscosity has been touted by manufacturers of weight loss supplements. Nonetheless, according to the U.S. Food and Drug Administration (FDA) and the Federal Trade Commission (FTC), there is not enough clinical data to support weight loss claims made by several manufacturers of glucomannan-containing dietary supplements.

This high viscosity is also accompanied by an increased risk for abdominal pain and esophageal obstruction (choking). While food containing glucomannan (in fully hydrated gel form) have been used for centuries, and are generally considered to be safe for adults without esophageal problems, numerous incidences of choking have led to recalls of dietary supplements and gel candies that contain glucomannan.

In light of the significant choking hazards posed by glucomannan in dry form, its use cannot be recommended in dry over-the-counter products such as tablets. In other dry forms (capsules, food sprinkle, etc), the product labels should clearly state that the product be taken with sufficient water to avoid choking.

Other food products that contain glucomannan must be thoroughly tested and optimized to minimize glucomannan's choking hazard. The product labels should also clearly state that the product should be cut into small pieces (if necessary) and chewed thoroughly before swallowing. Children and people with difficulty eating or swallowing should not be given glucomannan-containing foods.

For more information about glucomannan, please visit Natural Standard's Foods, Herbs & Supplements database.

References

1.Chmielewska A, Horvath A, Dziechciarz P, Szajewska H. Glucomannan is not effective for the treatment of functional constipation in children: A double-blind, placebo-controlled, randomized trial. Clin Nutr. 2011 Feb 12. View Abstract

2.Natural Standard: The Authority on Integrative Medicine. http://www.naturalstandard.com/

3.Sood N, Baker WL, Coleman CI. Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis. Am J Clin Nutr. 2008 Oct;88(4):1167-75. View Abstract

4.U.S. Food and Drug Administration. http://www.fda.gov/

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