Psyllium and glucomannan: gut, blood sugar and cholesterol effects
What it found
Psyllium has the strongest clinical support for normalising stools, moderating blood sugar and lowering LDL cholesterol, while glucomannan is a highly viscous, water-absorbing fibre that may support fullness, lipid control and weight management when taken with enough water.
The authors also discuss how these fibres fit into the nutritional context of GLP-1 receptor agonist therapy.
What they found
Studies in people
Stool normalisation
Psyllium absorbs water and forms a soft gel that can normalise stool consistency. It can increase stool bulk in constipation and improve stool form in loose stool or diarrhoea-prone states.
Blood sugar effects
Psyllium's gel layer slows glucose diffusion and carbohydrate absorption, reducing postprandial glucose peaks. In people with type 2 diabetes, psyllium supplementation has been linked to lower fasting plasma glucose and postprandial glucose responses.
Cholesterol and lipids
Psyllium modifies cholesterol absorption and bile acid turnover, contributing to lower LDL cholesterol. In randomised and metabolic studies, psyllium taken with meals reduced fasting glucose, postprandial glucose, total cholesterol, LDL cholesterol and triglycerides, and in some studies increased HDL cholesterol.
Glucomannan and satiety
Glucomannan has exceptional water-holding capacity and high viscosity, which can delay gastric emptying and prolong fullness. Clinical evidence suggests it may support weight management by increasing fullness and reducing energy intake when taken before or with meals.
Glucomannan and metabolism
In people with insulin resistance syndrome, konjac-mannan supplementation has been associated with improved glycemic markers and favourable lipid changes, including reductions in total cholesterol, LDL cholesterol and apoB-related risk markers.
Studies in people and animals
Gut bacteria and SCFAs
Fermentable fibres are broken down by gut bacteria into short-chain fatty acids such as acetate, propionate and butyrate. These metabolites support gut barrier integrity, immune regulation and gut hormone release, and may reduce low-grade inflammation.
What the authors conclude
“Psyllium has the strongest clinical support for stool normalization, glycemic modulation, and LDL cholesterol reduction, whereas glucomannan provides marked viscosity and water-holding capacity that may support satiety, lipid modulation, and weight-management strategies when appropriately hydrated and tolerated.”
Also in their conclusions
- They conclude that psyllium has the strongest clinical support for stool normalization, glycemic modulation, and LDL cholesterol reduction, whereas glucomannan provides marked viscosity and water-holding capacity that may support satiety, lipid modulation, and weight-management strategies when appropriately hydrated and tolerated.
- They suggest that a psyllium-centered, selectively glucomannan-supported strategy may help close the fiber gap and support bowel function, microbial metabolite signaling, and cardiometabolic stability during modern metabolic and weight-loss therapies.
- They advise that combined fiber supplementation should be individualized, with careful dose escalation and counseling for patients with severe constipation, gastroparesis, reduced fluid intake, swallowing difficulty, or multiple medications.
How it was done
The authors wanted to examine how psyllium and glucomannan act through gut viscosity, nutrient diffusion, bile acid and cholesterol handling, short-chain fatty acid production, gut barrier support, gut hormone signalling and low-grade metabolic inflammation, and to explore their role during modern weight-loss therapies.
The authors carried out a narrative review, searching PubMed/MEDLINE, Scopus, Web of Science and Google Scholar for studies on viscous dietary fibres, psyllium and glucomannan, gut bacteria, short-chain fatty acids, gut hormones, metabolic inflammation and GLP-1 receptor agonist therapy. They gave priority to randomised controlled trials, meta-analyses, systematic reviews and mechanistic studies, and integrated the evidence conceptually rather than performing a formal meta-analysis.
What it can’t tell you
- This is a narrative review, not a systematic review or meta-analysis, so it cannot provide a pooled quantitative estimate of effects.
- Direct clinical evidence that psyllium or glucomannan improves pain or mood outcomes remains limited, so those links are hypothesis-generating only.
- Most human evidence linking fiber intake to mood-related outcomes is observational, so causality cannot be established.
Who paid
- Conflicts
- The authors declare no conflicts of interest.
- Authors work at
- Hallym University College of Medicine, Republic of Korea; International Academy of Regenerative Medicine, Republic of Korea; International Academy of Musculoskeletal Medicine, China
The paper
- Title
- Psyllium and Glucomannan as Viscous Fiber Modulators of the Gut-Microbiome-Incretin Axis: Molecular Links to Metabolic Inflammation, Barrier Function, and GLP-1 Receptor Agonist Therapy
- Type
- ReviewThe authors read earlier studies and describe what they found. It isn’t a new study.
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Licence
- CC BY. Words in quotation marks are the authors’; the rest is our summary.
- Cite
- Yoon Y, Hwang J, Yang CM, et al (2026). Psyllium and Glucomannan as Viscous Fiber Modulators of the Gut-Microbiome-Incretin Axis: Molecular Links to Metabolic Inflammation, Barrier Function, and GLP-1 Receptor Agonist Therapy. International journal of molecular sciences. doi:10.3390/ijms27146287Free full textPubMed 42511630DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error