“Konjac glucomannan (KGM) supplementation appears to be a clinically relevant approach to alleviating functional constipation, with a potential mechanism being through enhancing the diversity and function of the gut microbiota,” wrote scientists from Southwest University in China in the European Journal of Nutrition. “These results further support the therapeutic potential of dietary fiber in regulating the gut ecosystem and improving gut health, particularly in athletes.”
Constipation is estimated to affect up to 20% of adults, with the problem being even more common among athletes.
According to this new article, high-intensity exercise can reduce blood flow to the gastrointestinal tract, thereby slowing its motility. A high-protein, low-fiber diet can also exacerbate colonic motility, and dehydration can make matters worse.
This has prompted some researchers to explore whether soluble dietary fiber, such as konjac glucomannan (KGM), can improve constipation symptoms. Some studies suggest that KGM may improve stool water content, regulate gut microbiota composition, and stimulate intestinal motility.
“However, clinical data remain limited in human populations, particularly among elite athletes,” the scientists wrote.
This new double-blind, randomized, controlled trial involved 48 elite male taekwondo athletes suffering from functional constipation. The athletes were randomly divided into two groups: one group received a placebo (3 grams of maltodextrin daily), while the other group received KGM (3 grams daily) for eight weeks.
Results showed that compared with placebo, a number of constipation measures were significantly improved, including the patient assessment of constipation symptoms (PAC-SYM), the patient assessment of constipation quality of life (PAC-QoL), bowel movement frequency (BMF), and bowel function index (BFI).
Microbiome analysis revealed that KGM increased the α-diversity and relative abundance of various genera, including *Lactobacillus*, *Bacteroides*, and *Phascolarctobacterium*. In contrast, the abundance of *Alistipes* and *Desulfovibrio* decreased.
The results showed that changes in the gut microbiota were closely associated with improved constipation symptoms. Further analysis revealed changes in several metabolic pathways, particularly those involved in biotin biosynthesis and nitrate reduction.
The researchers reported: “To our knowledge, this is the first study in human athletes to demonstrate that KGM can alleviate constipation-related symptoms by altering the composition of the gut microbiota. These results suggest that modulation of the gut microbiota may be a key mechanism by which dietary fiber exerts its therapeutic effects on gastrointestinal function.”
They concluded: “These results provide compelling evidence for the feasibility of dietary fibre supplementation in the treatment of functional constipation and highlight its potential as a non-pharmacological treatment for gastrointestinal dysfunction in athletes.”
Source: European Journal of Nutrition, 2025, 64, 303. doi: 10.1007/s00394-025-03826-3. “Effects of konjac glucomannan on gastrointestinal symptoms and gut microbiota in athletes with functional constipation: a double-blind, randomized controlled trial.” Authors: Y. Zhu et al.
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Post time: Dec-22-2025