Glucomannan
Also known as: konjac glucomannan, KGM, konjac fiber
Systematic reviews and meta-analyses report inconsistent effects on body weight (some analyses show small weight loss with low certainty, others show no significant effect). Moderate-quality evidence from RCTs supports LDL and non-HDL cholesterol reductions at roughly 3 g/day. In children with functional constipation glucomannan modestly increased defecation frequency but did not clearly improve stool consistency or treatment success.
Last reviewed: 2026-10-14 · 5 indexed studies
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Overview
Glucomannan is a highly viscous soluble fibre extracted from konjac (Amorphophallus konjac) used as a dietary supplement. Human trials and meta-analyses have examined effects on body weight, blood lipids and bowel function, with mixed results and frequent gastrointestinal side effects.
Mechanism & Function
Mechanism of Action
As a viscous soluble fibre glucomannan forms a gel in the gut, which can increase gastric volume and delay gastric emptying to promote satiety, bind bile acids and dietary cholesterol to reduce LDL, and increase stool bulk and transit to affect bowel frequency.
Physiological Role
Alters gastric/small‑intestinal contents viscosity, binds bile acids, increases faecal bulk and water content, and modulates appetite signals via delayed nutrient absorption.
Primary Pathways
Performance / Health Relevance
Limited direct relevance for athletic performance; potential indirect effects via body composition and bowel regularity may be relevant to some users.
Evidence Review
Practical Use & Dosage
- Minimum Effective Dose
- Approximately 3 g/day for LDL lowering (based on pooled trials)
- Optimal Range
- Not firmly established for weight loss; trials have used varying doses, often around a few grams daily
- Upper / Caution Level
- Not established
- Timing
- Often taken before meals to exploit bulk and satiety effects (trial details vary)
- Best Format
- Powder or capsules containing the soluble fibre
- Bioavailability
- Effect depends on intact viscous properties in the gastrointestinal tract; preparation and formulation may alter viscosity.
- Absorption Considerations
- Acts within the gut lumen; systemic absorption is negligible.
Safety & Interactions
Side Effects
- •Abdominal discomfort
- •Diarrhoea
- •Constipation
- •Flatulence
Contraindications
- Dysphagia or conditions with risk of oesophageal or intestinal obstruction if taken without adequate fluids
Drug Interactions
- •May affect absorption of orally administered medications by altering gastrointestinal transit or binding; time separation may be advisable
Who Should Avoid
- •Individuals with swallowing difficulties or oesophageal motility disorders
- •Those with known allergy to konjac products
Monitoring
Monitor gastrointestinal tolerance; consider spacing from other oral medications.
Frequently Asked Questions
Auto-generated from indexed evidence — dosage, safety, interactions, and more.
When is Glucomannan typically used or indicated?
Glucomannan is most commonly used for: Weight management, Cholesterol lowering, Relief of constipation / increase stool frequency. Alters gastric/small‑intestinal contents viscosity, binds bile acids, increases faecal bulk and water content, and modulates appetite signals via delayed nutrient absorption.
How does Glucomannan work?
As a viscous soluble fibre glucomannan forms a gel in the gut, which can increase gastric volume and delay gastric emptying to promote satiety, bind bile acids and dietary cholesterol to reduce LDL, and increase stool bulk and transit to affect bowel frequency.
What is the recommended dose of Glucomannan?
The optimal range is Not firmly established for weight loss; trials have used varying doses, often around a few grams daily. with a minimum effective dose of Approximately 3 g/day for LDL lowering (based on pooled trials). Best taken: Often taken before meals to exploit bulk and satiety effects (trial details vary). Upper / caution level: Not established.
What are the side effects of Glucomannan?
Reported side effects include: Abdominal discomfort; Diarrhoea; Constipation; and Flatulence. Monitoring: Monitor gastrointestinal tolerance; consider spacing from other oral medications.
Does Glucomannan interact with medications?
Known or theoretical interactions: May affect absorption of orally administered medications by altering gastrointestinal transit or binding; time separation may be advisable. Always check with a clinician before combining with prescription medication.
Who should avoid Glucomannan?
Glucomannan is generally not recommended for: Individuals with swallowing difficulties or oesophageal motility disorders; Those with known allergy to konjac products; and Dysphagia or conditions with risk of oesophageal or intestinal obstruction if taken without adequate fluids.
How strong is the evidence for Glucomannan?
Evidence level: Moderate (overall score 68/100), based on 5 indexed studies on SuppIndex.
Research & References (5)
Comparative effects of nutraceuticals on body weight in adults with overweight or obesity: A systematic review and network meta-analysis of 111 randomized clinical trials.
Network meta-analysis of 111 RCTs on nutraceuticals for weight loss in adults with overweight or obesity; glucomannan supplementation was associated with a small weight loss (mean difference -1.36 kg) but certainty of evidence was rated low.
A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B.
Systematic review and meta-analysis of RCTs assessing konjac glucomannan (KJM) effects on LDL, non-HDL cholesterol and apolipoprotein B. Twelve studies (n=370) showed significant reductions in LDL and non‑HDL cholesterol; authors suggested intake of ~3 g/day for these effects.
Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials.
Systematic review and meta-analysis of RCTs in children with functional constipation (3 RCTs, 122 participants). Glucomannan increased defecation frequency but did not significantly change stool consistency or overall treatment success.
The Impact of Glucomannan, Inulin, and Psyllium Supplementation (SolowaysTM) on Weight Loss in Adults with FTO, LEP, LEPR, and MC4R Polymorphisms: A Randomized, Double-Blind, Placebo-Controlled Trial.
Randomized, double‑blind, placebo‑controlled trial of a multi‑fibre supplement (glucomannan, inulin, psyllium) versus placebo in 112 adults with obesity and specific genetic polymorphisms over 180 days. The supplement group lost more weight and fat mass than placebo but reported a high incidence of gastrointestinal events (74.6%).
The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials.
Systematic review and meta-analysis of RCTs up to 2014 assessing glucomannan for weight loss. Meta-analysis of 8 RCTs found a non‑statistically significant difference in weight loss versus placebo (MD -0.22 kg) and noted variable study quality and gastrointestinal adverse events.
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Research Overview
Moderate EvidenceCite this ingredient
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Stable URL
https://thesuppindex.com/ingredients/glucomannan
SuppIndex. (2026). Glucomannan: Evidence summary, dosage and clinical studies. Retrieved October 16, 2026, from https://thesuppindex.com/ingredients/glucomannan
Based on 5 indexed studies · Evidence level: Moderate.
Goal Ratings
Stack Compatibility
Combining with other viscous fibres may increase gastrointestinal side effects; effects on weight when combined with other fibres have been reported but attribution to glucomannan alone may be uncertain.