What is Konjac Fiber?

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Konjac fiber is a water-soluble dietary fiber derived from the konjac plant. It is used in food products and as a dietary supplement. It is sold over the counter as glucomannan (amorphophallus konjac).

Konjac Fiber

Popularly called devil’s tongue and known as konnyaku in Japan, konjac fiber is a starch derived from the root of the konjac plant. Used for centuries in Asia, it is grown mainly in Japan and China. It is commonly available as glucomannan, the main component of the konjac root. This water-soluble dietary fiber contains glucose and mannose sugars. It has an extraordinarily high water-holding capacity--it can hold up to 200 times its weight in water--and is the most viscous of known dietary fibers.

Food Industry Uses

Konjac fiber is a natural vegetable gum and is also called konjac gum. It is used by the food industry as a thickener, gelling agent, emulsifier and stabilizer. In Asia, glucomannan is used in traditional foods such as noodles and tofu. Shirataki noodles, mostly made of glucomannan, are thin, translucent and chewy traditional Japanese noodles; they are thinner than wheat noodles, have a different texture and are low in calories and carbohydrates.

Dietary Supplement

Used as a supplement, the dietary fiber of the konjac root, glucomannan, can treat constipation, high cholesterol, high blood pressure and hypoglycemia (low blood sugar) and is used in weight loss, according to Ray Sahelian, M.D. Because of its water absorption capability, glucomannan helps promote weight loss by creating a feeling of fullness, leading to a decrease in appetite and caloric intake. As a soluble fiber, it reduces the metabolic impact of food by delaying gastric emptying and slowing the release of sugar into the bloodstream, reducing the insulin response. By interfering with the transportation of cholesterol and bile acids, it can decrease cholesterol levels. As a soluble fiber, it acts as a bulk-forming agent, helping with constipation.

How to Use It

Glucomannan can be found in powder, capsule and tablet form. It is available in stores where nutritional supplements are sold and online. For weight control, the dosage is about 1 g with a full glass of water before meals. According to an article in the "International Journal of Obesity," obese adults lost an average of 5.5 pounds of body weight--without changing their eating or exercise patterns--while taking 1 g of glucomannan fiber one hour before each meal for eight weeks.

Possible Side Effects

The eVitamins website reports that glucomannan, a soluble fiber, can bind with and reduce the absorption of nutrients--which can be handled by taking a multivitamin. When first using konjac fiber as a dietary supplement, begin with a small amount and gradually increase the dosage. Drink at least 8 oz. of water with all forms of glucomannan, especially pill form, due to the chance that the contents of the pill may become lodged in the esophagus, absorb fluid and then expand, creating an obstruction. There may be sensitivity to inhaled glucomannan. The high fiber content may produce intestinal gas, leading to abdominal discomfort and flatulence, especially in people not accustomed to a high-fiber diet. There are no well-known drug interactions.

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