November 8, 2022

Can Glucomannan Cause Constipation | Studies Breakdown

by Bryan Wellington

Dietary supplements are used by millions of Americans every day, and there are dozens of types and varieties. One of the most popular new ingredients in weight loss products is Glucomannan, the derivative main component of the Konjac Root of Southeast Asia. According to Business Wire, the North American Konjac Root market is set to increase by over 6% year on end.

With this popularity, it’s prudent to examine the effects of this surging supplement–both good effects and bad.

In this article, I’ll look at several scientific studies to determine if constipation is a real side effect of Glucomannan and Konjac, or if it might even be a laxative.

Key Findings

✲ No indications are given in clinical studies of constipation side effects

✲ Several studies, rather, have seen laxative benefits of glucomannan.

Special efficacy of glucomannan as a laxative was seen with probiotic complements.

Glucomannan as a laxative proved effective for all age ranges.

No Evidence of Constipation

I’ve reviewed dozens of glucomannan studies scoring for any and all signs of constipation as a side effect. The three best-written studies (from the Journals Obesity, Metabolism, and Clinical Nutrition) found no evidence or indications of constipation.

The most commonly analyzed compound of the Konjac root is its fiber. It is this very fiber that is the most responsible for the laxative benefits discussed next.

Evidence of Laxative Benefit

Contrary to causing constipation, all the evidence to date shows that Glucomannan fiber from the Konjac Root can have laxative benefit. This benefit extends even to those who currently suffer from constipation.

Two separate studies, one on humans and one on laboratory animals, found improvements in bowel movement and ecology of stool (an important secondary outcome showing benefits to total gastro-intestinal (GI) health). Both of these studies were conducted on clinically constipated individuals.

Another group of researchers specifically looked at how glucomannan may help children suffering from constipation. In their first set of experiments, they looked at children suffering from neurological conditions that impair their bowel movements. Not only was the Glucomannan effective, but it was also seen as a safe treatment.

These same researchers later took their trials and expanded them to healthy children, to see if the benefits translated, and they did. These two studies taken together indicate that the laxative benefit is playing out through GI mechanisms that could be extended to all age ranges.

A Second Benefit

Lastly, I’ll draw brief attention to a study that compared the two most impactful components of the Konjac Root. The first, which we’ve already discussed, is the fiber. The second component is its oligosaccharides. 

Oligosaccharides are combinations of sugars that act as signalers to link up with lipids (fats) and amino acids (proteins). A study looking at what, exactly, in Konjac Root producing laxative effects, found surprising evidence that it is in fact the oligosaccharides.

None of their study indicates that Glucomannan is not effective, only that the oligosaccharides might be more effective. The takeaway from this may be that konjac root supplements may be more beneficial than extracts of only the fiber.


Glucomannan and its parent plant, the Konjac Root, have become buzzwords in supplement circles. At least for constipation, it appears that there is no risk of constipation. Instead, it has impressive laxative effects.


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