Supplement evidence

077 / 575Fiber & digestive

Glucomannan

View my plan →

The short answer

A viscous fiber that can aid constipation and modest weight or LDL outcomes in some trials.

Evidence and scope: Conditional or population-specific
This status does not grade the ingredient for every goal, outcome, or person.
Important limitation: Benefit depends on the population, formulation, baseline status, and objective; results should not be generalized.
Before deciding: Key concern: Swallowing difficulty, bowel obstruction, and medicine absorption are major concerns.

01 / PRACTICAL GUIDE

Dose, absorption, and combinations

These are indication-specific reference or studied ranges—not a personalized prescription. Start with the objective, then check the form, label, medicines, and health conditions.

Reference range by objective

Constipation1 g one to three times daily

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

weightAbout 3 g/day before meals in many trials

Reference or studied range—not a personalized prescription. The product label or a clinician may specify a different dose.

Dose source ↗

More is not automatically better. A clinician or product label may specify a different amount.

Absorption / solubilityFat/water classification is not the key factor

Fat/water solubility is not the useful decision point; preparation, fluid, timing, or strain identity matters more.

How it is commonly taken

Take with at least 250 mL water per dose.

Do not combine casually

Swallowing difficulty, bowel obstruction, and medicine absorption are major concerns.

Dose and use source ↗

Dose and use links lead to primary or official source material. Search links are discovery tools, not proof that every returned paper applies.

02 / EVIDENCE

What the research says

We keep supportive, mixed, negative, safety, and contextual findings together. The headline never replaces the underlying papers.

3research papers in this ledger

8unique primary studies represented

103unique participants represented

These are audited counts for this JIVANA collection, not search-result totals. Participants are counted once when multiple papers use the same cohort; review papers are not added again to participant totals.

Open the research timelineResearch timeline

Entries are ordered by publication year. A study period appears only when the source reports it.

2019

Does not support the tested claimPMID 31036412 · NCT02280772

No effect of glucomannan on body weight reduction in children and adolescents

Glucomannan did not improve BMI-for-age. LDL and total cholesterol were lower, but systolic or diastolic blood pressure was higher at selected follow-ups; these secondary findings require cautious interpretation.

Published: 2019Duration: 12 weeks treatment plus 12 weeks follow-upn=96 participants

Study design and methods

Design: Randomized, double-blind, placebo-controlled trial
Population: 96 children aged 6–17 with overweight or obesity
Intervention: Glucomannan 3 g/day or maltodextrin placebo plus dietary and lifestyle advice
Outcome: BMI-for-age z score, lipids, blood pressure, and adverse events

Open research record ↗

2015

Mixed or qualifiedPMID 25701331

The effect of glucomannan on body weight in overweight or obese children and adults

Some adult trials reported short-term weight changes at selected time points, but only one found benefit at more than one time point and none improved BMI. Child data were too limited; the abstract did not report an aggregate participant count.

Published: 20156 primary studies represented

Study design and methods

Design: Systematic review of 6 randomized placebo-controlled trials
Population: Otherwise healthy adults and children with overweight or obesity
Intervention: Glucomannan versus placebo; doses and durations varied
Outcome: Body weight and BMI

Open research record ↗

2008

Mixed or qualifiedPMID 18460488

Konjac glucomannan in constipated adults consuming a low-fiber diet

Weekly bowel movements increased from 4.1 to 5.3 with slight symptom improvement, but the uncontrolled sequence and sample of seven cannot establish a reliable constipation benefit.

Published: 2008Duration: 21-day placebo period, 7-day adaptation, and 21-day glucomannan periodn=7 participants

Study design and methods

Design: Diet-controlled, nonrandomized linear intervention study
Population: 7 adults with constipation
Intervention: Konjac glucomannan 1.5 g three times daily after a placebo period
Outcome: Bowel frequency, stool characteristics, symptoms, and fecal microbiology

Open research record ↗

Unscreened discovery appendix—not evidence12 candidate publicationsSearch run: Aug 21, 2026

Complete for the displayed PubMed query at the search timestamp—not for all databases or every possible synonym. Candidates can be irrelevant, duplicate the same study, or report negative findings. They are never summed as evidence or participants until screened.

03 / SOURCES

Start with the source material

Official evidence overviewPubMed bounded human-evidence search Live PubMed discovery searchNational Library of Medicine

The live search is for discovery only. Search-result counts change and are not included in the audited totals above.

Recent PubMed discovery recordsDirect links to the first 12 records returned by the reproducible search. These are discovery candidates—not reviewed summaries or a count of supportive findings.

04 / EXPERT CONTEXT

Expert context—not evidence

Expert positions are dated context—not scientific evidence. They never raise the evidence status or become consensus by repetition.

No direct, source-verified endorsement is currently recorded. Research authorship or discussion alone is not treated as endorsement.