Glucomannan for Herbal Naturopathy: properties, benefits, uses, side effects

Glucomannan is a dietary fiber extracted from the root of the Amorphophallus konjak plant and used in diets because it reduces the absorption of fats, carbohydrates and cholesterol. Let’s find out better.

What is Glucomannan

Glucomannan is a plant- based polysaccharide composed of many units of glucose and mannose. It is a non-assimilable dietary fiber and therefore of practically no contribution.

Glucomannan is extracted in large quantities from the tuberous root of Amorphophallus konjak K. Koch, a plant of oriental origin, used for millennia in the Japanese dietary tradition.

Glucomannan is used in the treatment of obesity and in diets because it reduces the absorption of lipids and sugars.

Where is glucomannan found?

Glucomannan is mainly extracted from Konjak and the name is generally associated with this plant. Actually glucomannan is a polysaccharide found in other plants such as aloe and plantain.

Amorphophallus konjak K. Koch is native to the tropical and sub tropical climates of extreme Asia. Belonging to the Araceae family family, it is a perennial herbaceous plant, which grows with a single stem that can reach 25 cm in diameter, the single leaf is up to 1.3 m long, bipinnata and divided into numerous leaflets. The flower is a spadix (similar to that of calla lilies) up to 55 cm long.

Konjak has been used as a food in Japan since the sixth century. Today it has spread to the rest of the world for its use in diets and as a substitute for low-calorie meals in noodles with the name of shirataki.

Properties of glucomannan

Glucomannan is used as a powder and is capable of swelling quickly by gelling in water, up to absorbing 60 times its weight.

At the intestinal level it is hydrolyzed (split into smaller molecules) by the bacterial flora, but in any case it is not assimilable and does not bring any nutritional or caloric value to the diet. On the other hand, acting as dietary fiber, it reduces the absorption of fats, carbohydrates and cholesterol, stimulates peristalsis and evacuation. It also acts by promoting the sense of fullness and satiety.

Glucomannan is useful in the treatment of overweight and obesity, especially when associated with a low-calorie diet, because it reduces the absorption of carbohydrates and lipids, as well as controlling blood sugar. It also works by reducing cholesterol, LDL and triglyceride levels. Several studies have highlighted how this action could be determined by the intestinal sequestration of bile salts and, consequently, by the reduced absorption of cholesterol and fatty acids.

Finally, glucomannan can be inserted among the laxatives for the mechanical stimulation action on peristalsis.

The recommended doses are 1-2 g per day.


Glucomannan has no significant side effects.

The only note are some reports of suffocation found in the USA by a group of children who had eaten snacks containing konjac, due to the gelling effect of the polysaccharide.

The use of glucomannan as a gelling agent in snacks. In spite of other gelling agents, konjac creates harder structures that do not disintegrate easily in the mouth.

It is therefore advisable to carefully chew konjack-based products on the market and used as meal replacements.

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