What Is the Japanese Plant Konjac Mannan?

Konjac mannan fiber is incorporated into weight-loss regimens.

Konjac, devil's tongue and voodoo lily are common names for Amorphophallus konjac. Cooked konjac tubers yield an edible fibrous substance called glucomannan that is a staple in Japan. Certain therapeutic benefits of glucomannan, or konjac mannan, are widely promoted in the health food industry. The validity of such claims is under serious study by international governmental food safety agencies. It remains that konjac mannan is a safe food, whatever the results.

Amorphophallus konjac

Amorphophallus konjac is in the large Araceae family of plants. Dieffenbachia (dumb cane) and spathiphyllum (peace lily) are related houseplants. The giant, malodorous Amorphophallus titanum and the exotic florists' flower Anthurium are Araceae plants. The konjac plant is native to tropical and sub-tropical regions. It produces a dark-purple spadix, or flower stalk, nearly 2 feet long. The surrounding spathe is pink or purple. The konjac plant produces a rather flat, round edible tuber about 10 inches across. Cooked tubers are reduced to a stiff, gelatin-like substance and pressed into blocks. The Japanese purchase it in local grocery stores.

Konjac mannan

Glucomannan, commonly called konjac mannan, is the primary component of the konjac tuber. The substance is low in calories and high in dietary fiber. The Japanese consider it a digestive cleanser and de-toxifier. The European Food Safety Authority was requested by the European Commission to asses the validity of various health benefit claims for konjac mannan. The U.S. Food and Drug Administration warns promoters that unsubstantiated claims constitute the product a drug.

Diabetes

The Panel on Dietetic Products, Nutrition and Allergies investigated claims that consuming konjac mannan results in stabilizing and maintaining healthy blood sugar and blood lipid levels. The Panel provided the EFSA with an assessment of existing studies with information provided by Member States. It concluded that cause and effect relationships have not been established between konjac mannan consumption and reduced post-prandial glycaemic responses, the maintenance of normal blood sugar, or the control of triglycerides. A favorable relationship with cholesterol control is established. A study by the U.S. National Institutes of Health concluded that konjac mannan may improve the effectiveness of conventional treatments for type 2 diabetes.

Weight Loss

The Panel found a statistically significant effect on body weight reduction when konjac mannan was used along with an energy-restricted diet. The Panel acknowledged that the consumption of konjac mannan with water before meals, along with a low-calorie diet, produced the desired effect in overweight adults. The Panel concluded that a total intake of 3,000 mg spread throughout the day is the minimum therapeutic dose. No cause and effect relationship was established for improved bowel function or decreased pathogenic gastro-intestinal microorganisms.

References

• University of Hawaii: Botany Department - Araceae
• University of Connecticut; Amorphophallus konjac; K. Koch; August 9, 2011
• European Food Safety Authority; Scientific Opinion ... ; EFSA Panel ...; December 9, 2010
• U.S. Food and Drug Administration; Department of Health ... ; Certified Mail; Dear Mr. Josephs; April 25, 2005
• National Center for Biotechnology Information; Konjac-Mannan (Glucomannan) Improves Glycemia...; Vuksan, V., et al.; June 22, 1999