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What is glucomannan and how can it help us lose weight?

We can usually read that glucomannan is the “only proven supplement that helps you lose weight .” This statement is correct, but you have to understand why. Indeed, glucomannan can facilitate the control of the amount of food we eat and, with it, the daily calories . That does not mean that it is necessary to take into account some important considerations. How does this food supplement work?


What is and what is not glucomannan

The glucomannan is listed as a food supplement according to the European Union, ie, not a food nor a drug. Actually, glucomannan is a highly hydratable fiber . This means that it is a substance that, when we give it water, swells rapidly and grows, creating a viscous paste that takes up much more of its original volume.

In particular, glucomannan has a higher molecular weight and viscosity than any known fiber . Like other fibers, glucomannan is not digestible and passes through our digestive system without pain or glory, gently, dragging part of the swallowed content. This is a very long polysaccharide with units of D-mannose and D-glucose 1.6: 12, and with ramifications every 50 or 60 units, approximately. Because of its molecular configuration, our enzymes can not attack glucomannan, which is why it is not nutritious (or has no bioavailability)


The polysaccharide is usually obtained from an Asian plant known as konjac, Amorphophallus konjac . Glucomannan is extracted from the root, although the plant has always been used in a traditional way in Asia, as an edible plant, consuming bulbs, making gelatin and other culinary uses

In addition, on a commercial level, glucomannan is used in a different way. The most popular form, probably, is pasta . The glucomannan paste, also known as konjac, by the plant of origin, is, in nutritional terms, very poor. This contributes about 20 Kcal, or less, per serving (depending on the manufacturer), which represents less than 10% of the caloric intake of a traditional pasta.

How glucomannan is used

The use of glucomannan differs according to the format in which we consume it. If it is in pasta, as we said, you just have to cook it in a very similar way to how the traditional one is cooked. In the case of taking pills, it is usually advised to take between 2 and 3 grams a day, half an hour before the meal, with water.


The fiber will swell hydrating and generating a feeling of satiety. This fiber becomes a viscous paste in the stomach, mixed with food. In this way, it helps intestinal transit, like other water-soluble fibers. According to several studies, glucomannan can help reduce constipation , promotes glycemic control and has probiotic effects . However, the most appreciated quality of this polysaccharide, without a doubt, is satiating.

The latter is the one that is due to fame as an effective substance to lose weight . There are studies that indicate that glucomannan helps in weight control plans , although it should be noted that this is due to its origin as a fiber, and not due to any direct metabolic action: it simply satisfies but does not contain kilocalories that we can assimilate. This also has its downside.

The negative effects of glucomannan

In principle, glucomannan is harmless. However, we can find some potentially dangerous situations . The first one is related to its great capacity to absorb water. Glucomannan was banned in 2003 as a culinary gelatin in confectionery due to the danger it poses for children, patients with esophageal problems and the elderly. This danger is basically due to the fact that it can cause suffocation due to obstruction of the upper respiratory tract .

Another problem of glucomannan is also present in other fibers, since it has a tendency to drag the digested food , reducing the passage time through the intestine and contact with the intestinal mucosa. This means that it reduces the assimilation of nutrients, which in a normal diet should not be a major problem, but in the long run it can cause problems of malnutrition.

We see this, for example, in the reduction of the acquisition of liposoluble vitamins . Eliminating bile acids prevents the assimilation of vitamins such as E, A, D and K. Over time, this decrease can be significant, nutritionally speaking. The same problem we see with drugs.

Fibers such as glucomannan, in the same way, can reduce the absorption of fat-soluble drugs , so that in case of being under treatment, the use of this type of food supplements is strongly discouraged. In short, glucomannan has no other known interactions, so it is harmless, or even a very effective satiating, in moderate amounts.

Last, and not least, glucomannan consumption may displace other healthier options . Remember that this fiber does not provide nutrients, just satiate, and has no flavor. This can lead us to consume it with very caloric commercial sauces, with fats of poor quality and high salt content and low nutritional value. In short, glucomannan can be a great ally, but only if we know how to use it properly.

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