Home / Carbohydrates / Glucomannan or Konjac Gum

Glucomannan or Konjac Gum

What is glucomannan or konjac gum?

Glucomannan or konjac gum is a viscous soluble fiber extracted from the root of the konjac plant (Amorphophallus konjac), native in Asia ^[1]. It is an indigestible carbohydrate, a polysaccharide made of glucose and mannose. It can absorb 100 times its weight of water. Glucomannan is almost completely fermentable by the normal colonic bacteria ^[2], but, according to claims on certain products, it provides no or only few calories ^[1].

Glucomannan as a Food Additive

Glucomannan may be used as a thickener and emulsifier in fruit juices, yogurts, ice creams, and other foods. It is used in Japan and other Asian countries to make “low-carb, low-calorie” shirataki noodles and konjac cakes, chips and jams. In the European Union it is labeled as E number E425 ^[3].

Glucomannan (Konjac Gum) Supplements

Konjac root supplements as tablets, capsules or powder are available over-the-counter (OTC).

Possible Glucomannan Health Benefits

Glucomannan supplements are POSSIBLY EFFECTIVE in:

In several studies, glucomannan supplements in a dose 3-4 grams/day for at least 8 weeks was associated with reduction of the total cholesterol (by up to 20 mg/dL), LDL cholesterol (by up to 15 mg/dL) and triglyceride levels in obese and healthy individuals; HDL cholesterol levels were not affected ^[6,9,11,12].

There is INSUFFICIENT EVIDENCE about glucomannan effectiveness in prevention or treatment of chronic constipation in children ^[4,5,7], diverticular disease, hemorrhoids, lung cancer ^[6], acne, gastrointestinal infections ^[7], obesity in children ^[10], high blood glucose levels in diabetes mellitus ^[7,12], high blood pressure ^[12] or promoting weight loss in adults ^[7,8,9,12] or children ^[10].

Glucomannan Safety: Toxicity, Side Effects

Glucomannan (konjac gum) is currently not Generally Recognized As Safe (GRAS) by the US Food and Drug Administration (FDA).

Glucomannan has to be taken with at least 1 cup of water or other fluid to prevent chocking, throat, esophageal or bowel obstruction (from this reason, a tablet form of glucomannan was banned in Australia), and should not be taken immediately before bed ^[6]. Possible side effects include abdominal bloating, excessive gas (flatulence) and diarrhea ^[6].

Due to the danger of hypoglycemia, diabetics should speak with a doctor before taking glucomannan ^[6]. Toxic effects of glucomannan are not known.

Pregnancy. Insufficient studies about glucomannan have been done to evaluate its safety during pregnancy and breastfeeding ^[6].

Related Nutrients

Prebiotic PatentGenius
Matsuura Y, 1998, Degradation of konjac glucomannan by enzymes in human feces and formation of short-chain fatty acids by intestinal anaerobic bacteria PubMed
Current EU approved additives and their E Numbers Food Standards Agency
Loening-Baucke V et al, 2004, Fiber (glucomannan) is beneficial in the treatment of childhood constipation PubMed
Chmielewska A et al, 2011, Glucomannan is not effective for the treatment of functional constipation in children: a double-blind, placebo-controlled, randomized trial PubMed
Glucomannan Drugs.com
Scientific Opinion on the substantiation of health claims related to konjac mannan (glucomannan) and reduction of body weight, reduction of post-prandial glycaemic responses, maintenance of normal blood glucose concentrations, maintenance of normal (fasting) blood concentrations of triglycerides, maintenance of normal blood cholesterol concentrations, maintenance of normal bowel function and decreasing potentially pathogenic gastro-intestinal microorganisms European Food Safety Authority
Onakpoya I et al, 2014, The efficacy of glucomannan supplementation in overweight and obesity: a systematic review and meta-analysis of randomized clinical trials PubMed
Glucomannan uses WebMD
Livieri C et al, 1991, The use of highly purified glucomannan-based fibers in childhood obesity PubMed
Arvill A et al, 1995, Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men The American Journal of Clinical Nutrition
Sood N et al, 2008, Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis The American Journal of Clinical Nutrition