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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
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