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What is it? Overview Usage Side Effects and Warnings

What is Glucomannan?

Glucomannan is a dietary fiber derived from the tubers of Amorphophallus konjac. Konjac flour (made from these tubers) is used to make a jelly called konyaku, a common food product in Japan.

Fiber-containing foods, such as oats, are known to help reduce cholesterol and improve constipation and may also help regulate blood sugar and assist in weight reduction by creating a feeling of fullness. However, many people have a hard time consuming enough fiber from food, so turn to fiber supplements, such as guar gum and pectin, to help fulfill their daily requirements. Glucomannan offers one advantage over these forms of fiber: much smaller doses are necessary. When glucomannan is placed in water, it can swell up to 17 times its original volume. These qualities make it potentially quite...

Several small controlled studies have found glucomannan to be effective for improving the cholesterol profile. 1 Glucomannan appears to reduce LDL ("bad") cholesterol and, according to some studies, increase HDL ("good") cholesterol. In addition, it may improve blood pressure .

By expanding in the stomach, glucomannan might be useful for people trying to lose weight. Many people report a feeling of fullness after taking glucomannan, and some studies found a significant weight loss among those taking glucomannan compared to those on placebo . 2 3 4 5 However, not all studies of glucomannan for weight loss have had positive results. 6 Glucomannan may also help the body to regulate blood sugar levels, and therefore could be helpful in treating diabetes . 7...

Safety Issues

In Japan, food products containing glucomannan have a long history of use and are believed to be safe. However, there are some concerns about taking glucomannan as a supplement.

Some people taking glucomannan complain of excess gas, stomach distension, or mild diarrhea. These symptoms usually abate within a couple of days of treatment or with a reduction of the dosage.

In a few cases, glucomannan tablets have caused obstruction of the esophagus when they expanded before reaching the stomach. 8 In response to these reports, tablets of this type have been banned. Capsules, however, do not seem to pose the same risk because their casing prevents the glucomannan from contacting water until it reaches the stomach. The dramatic expansion of glucomannan has also raised...