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Glucomannan

Supplement soluble fiber gutgeneral nutrition
Aka: konjac fiber, Amorphophallus konjac
Brands seen in Singapore: NOW Foods, Nutricost, Absolute Nutrition, Nature's Way, Best Naturals
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Konjac fibre that swells in water · little weight effect
When to take
Trials dosed 1–1.33 g before each meal
Take with
Water · tablet forms have blocked the esophagus
Pros & cons
Pros
  • Absorbs up to 50 times its weight in water
  • FDA counts glucomannan toward dietary fibre
  • Short-term side effects reported were minor
Cons
  • 2015 review of 6 trials: no significant weight effect
  • Tablet forms linked to 7 esophageal obstructions
  • Belching, bloating, flatulence and diarrhea reported
Sources
  1. NIH ODS — Dietary Supplements for Weight Loss (Health Professional), updated 18 May 2022; read via the archive.org capture of 26 Aug 2026 because ods.od.nih.gov returns HTTP 403 to direct fetches — Glucomannan section, source and mechanism · read 2026-08-27
    what it says
    “Glucomannan is a soluble dietary fiber derived from konjac root (Amorphophallus konjac) that can absorb up to 50 times its weight in water … proposed to increase feelings of satiety and fullness and prolong gastric emptying”
  2. NIH ODS — Dietary Supplements for Weight Loss (Health Professional), updated 18 May 2022; read via the archive.org capture of 26 Aug 2026 because ods.od.nih.gov returns HTTP 403 to direct fetches — Table 1 summary row for glucomannan · read 2026-08-27
    what it says
    “Glucomannan … Research findings: Little to no effect on body weight … Significant safety concerns reported for tablet forms, which might cause esophageal obstructions, but few safety concerns with up to 15.1 g/day of other forms for several weeks”
  3. NIH ODS — Dietary Supplements for Weight Loss (Health Professional), updated 18 May 2022; read via the archive.org capture of 26 Aug 2026 because ods.od.nih.gov returns HTTP 403 to direct fetches — 2015 systematic review · read 2026-08-27
    what it says
    “The authors of a 2015 systematic review of six randomized controlled trials with a total of 293 participants concluded that 1.24 to 3.99 g/day glucomannan for up to 12 weeks does not have a significant effect on body weight”
  4. NIH ODS — Dietary Supplements for Weight Loss (Health Professional), updated 18 May 2022; read via the archive.org capture of 26 Aug 2026 because ods.od.nih.gov returns HTTP 403 to direct fetches — how the trials dosed it · read 2026-08-27
    what it says
    “consumed 3 g/day glucomannan (1 g before each meal) or placebo for 8 weeks … supplementation with glucomannan (1.33 g before each meal for a total of 3.99 g/day)”
  5. NIH ODS — Dietary Supplements for Weight Loss (Health Professional), updated 18 May 2022; read via the archive.org capture of 26 Aug 2026 because ods.od.nih.gov returns HTTP 403 to direct fetches — long-term safety, side effects and the obstruction reports · read 2026-08-27
    what it says
    “Little is known about the long-term safety of glucomannan … minor adverse effects, including belching, bloating, loose stools, flatulence, diarrhea, constipation, and abdominal discomfort … seven cases of esophageal obstruction in 1984–1985 in Australia”
  6. NIH ODS — Dietary Supplements for Weight Loss (Health Professional), updated 18 May 2022; read via the archive.org capture of 26 Aug 2026 because ods.od.nih.gov returns HTTP 403 to direct fetches — interactions section · read 2026-08-27
    what it says
    “glucomannan and guar gum might decrease the absorption of many drugs that are taken orally … Glucomannan has been reported to lower blood glucose levels and, therefore, could interact with diabetes medications”
  7. US FDA — Questions and Answers on Dietary Fiber (page current as of 25 July 2024), actions taken on dietary fiber · read 2026-08-27
    what it says
    “January 2020: FDA added “glucomannan” to the existing list of isolated or synthetic non-digestible carbohydrates that FDA intends to propose to be added to the definition of dietary fiber.”
  8. HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. No. 001 (October 2025) — Annex A (118 rows) and Annex B (4 rows): glucomannan / konjac / Amorphophallus konjac is NOT LISTED in either; Annex A runs 51. Ginkgo biloba then 52. Gluta usitata, with no glucomannan between them · read 2026-08-27
    what it says
    “The objective of this guideline is to highlight the substances of concern when used in HS and TM and is not meant to be an exhaustive list.”
  9. HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 (January 2026), clause 4.8 with Tables 4–5, which list vitamins and minerals only — no botanical or fibre rows · read 2026-08-27
    what it says
    “4.8 HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5.”
  10. iHerb Singapore — Glucomannan category page, default listing order, 27 Aug 2026 · read 2026-08-27
    what it says
    “1 - 15 of 15 results: NOW Foods, Glucomannan, 575 mg; Nutricost, Glucomannan Konjac Root Extract; NOW Foods, Glucomannan, Pure Powder; Absolute Nutrition, Absolutely Full; Nature's Way, Glucomannan from Konjac Root; Best Naturals, Konjac Root”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.