Glucomannan is a fiber found in the root of the elephant yam. It has been used to promote weight loss and ease constipation. It can be taken as a pill or powder.
3 to 5 grams once daily
What Research Shows
Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.
It may be safe for most adults to take glucomannan as a powder for a short time. Pills or tablets with glucomannan may not be safe. Not enough studies have been done to say whether it is safe to take for a long period.D1-D3
Talk to your doctor about any alternative therapy or supplements you are taking to make sure it does not interfere with your current treatment. For example:
A. Constipation in Children
A1. Chmielewska A, Horvath A, et al. Glucomannan is not effective for the treatment of functional constipation in children: a double-blind, placebo-controlled, randomized trial. Clin Nutr. 2011 Aug;30(4):462-468.
A2. Han Y, Zhang L, et al. Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomised controlled trials. Asia Pac J Clin Nutr. 2017 May;26(3):471-477.
B1. Martino F, Puddu PE, et al. Low dose chromium-polynicotinate or policosanol is effective in hypercholesterolemic children only in combination with glucomannan. Atherosclerosis. 2013 May;228(1):198-202.
B2. Ho HVT, Jovanovski E, et al. 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. Am J Clin Nutr. 2017;105(5):1239-1247.
B3. Jenkins AL, Morgan LM, et al. Co-administration of a konjac-based fibre blend and American ginseng (Panax quinquefolius L.) on glycaemic control and serum lipids in type 2 diabetes: a randomized controlled, cross-over clinical trial. Eur J Nutr. 2018 Sep;57(6):2217-2225.
C1. Onakpoya I, Posadski P, et al. The effect of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr. 2014;33(1):70-78.
C2. Zalewski BM, Chmielewska A, et al. The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials. Nutrition. 2015 Mar;31(3):437-42.e2.
D1. Health Canada advises Canadians that natural health products containing glucomannan may cause serious choking if used with insufficient fluid. Available at: http://www.healthycanadians.gc.ca/recall-alert-rappel-avis/hc-sc/2010/13439a-eng.php. Published January 29, 2010. Accessed April 18, 2019.
D2. Inspections, compliance, enforcement, and criminal investigations. US Food & Drug Administration website. Available at: https://www.fda.gov/ICECI/EnforcementActions/EnforcementStory/EnforcementStoryArchive/ucm105953.htm. Updated May 2, 2016. Accessed April 18, 2019.
D3. Vanderbeek PB, Fasano C, et al. Esophageal obstruction from a hygroscopic pharmacobezoar containing glucomannan. Clin Toxicol (Phila). 2007;45:80-82.
Last reviewed February 2020 by EBSCO NAT Review Board Eric Hurwitz, DC
Last Updated: 5/27/2020
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