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Glucomannan Fiber Benefit and Side Effects, Use for Losing Pounds and Satiety

Glucomannan Fiber Benefit and Side Effects, Use for Losing Pounds and Satiety

Glucomannan root is a water soluble dietary fiber that has been used in East Asia for more than a thousand years. This dietary fiber is the main polysaccharide obtained from the tubers of the Amorphophallus konjac plant. The chemical structure consists, mainly, of mannose and glucose. Glucomannan fiber has a extraordinarily high water holding capacity, forming highly viscous solutions when dissolved in water. Glucomannan has the highest molecular weight and viscosity of any known dietary fiber. Glucomannan is effective for weight loss due to the satiety sensation that it produces. Glucomanna is also a remedy for constipation because it increases fecal volume. Glucomannan firber may be considered as a substance to lower cholesterol levels since it interferes in the transport of cholesterol and of bile acids.

Glucomannan fiber is found in an effective diet pill called Diet Rx which helps you eat less.

Glucomannan Side Effects

No major glucomannan side effects have been reported in the medical literature as of 2009 except for case reports as listed below. Due to its ability to absorb water, constipation could occur if little water in ingested. High amounts of glucomannan could lead to gastrointestinal side effects mostly of stomach cramps and intestinal upset.

Nature’s Way Glucomannan


Glucomannan ( Amorphophallus konjac ) is a 100% dietary fiber source obtained from the root of the konjac plant. Glucomannan is an excellent addition to a sensible weight loss program. This glucomannan product is especially grown and prepared to Japan according to exacting specifications.

Glucomannan has the ability to absorb up to 50 times its weight in water.

Supplement Facts, 3 capsules

Glucomannan (root) – 1.99 grams

Glucomannan and Weight Loss

Certain fiber supplements added to a low caloric diet have additional effects on weight reduction in overweight subjects. Glucomannan induces body weight reduction in healthy overweight subjects. Glucomannan supplement does not appear to have any significant side effects.

Experiences with Three Different Fiber Supplements in Weight Reduction.

Med Sci Monit. 2005. Birketvedt GS, Shimshi M, Erling T. Laboratory of Gastroenterology, Institute of Clinical Medicine, University of Tromsø, Tromsø, Norway.

Researchers at Institute of Clinical Medicine, University of Tromsø, Tromsø, Norway comparde the effect of various commercial fiber supplements (glucomannan, guar gum and alginate) on weight reduction in healthy overweight subjects. One hundred and seventy six men and women were included to receive either active fiber substance or placebo in randomized placebo-controlled studies. The fiber supplements consisted of the viscous fibers glucomannan (Chrombalance), glucomannan and guar gum (Appe-Trim) and glucomannan, guar gum and alginat (Glucosahl). All fiber supplements plus a balanced 1200 kcal diet induced significantly weight reduction more than placebo and diet alone, during a five week observation period. However, there were no significant differences between the different fibers in their ability to induce weight reduction. Glucomannan induced body weight reduction in healthy overweight subjects, whereas the addition of guar gum and alginate did not seem to cause additional loss of weight. No significant glucomannan side effects were reported.

Effect on Cholesterol

The use of glucomannan can reduce serum cholesterol levels. Glucomannan and a combination of glucomannan and plant sterols substantially decreases plasma LDL cholesterol concentrations. Glucomannan may even be used in children who have high cholesterol levels.

Konjac Glucomannan and Constipation

Konjac glucomannan relieves constipation since it increases stool bulk and improves colonic ecology. Konjac glucomannan supplement use promotes colonic fermentation, indicated by a decrease in fecal pH and increased fecal short-chain fatty acid concentrations. Supplementation of Konjac glucomannan to a low-fiber diet enhances defecation frequency, possibly by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation.

Glucomannan is beneficial in chlidren in the treatment of constipation with and without encopresis.

Glucomannan Beneficial for the Colon

Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults.

Nutrition. 2006. Institute of Nutritional Science, Chung Shan Medical University, Taichung, Taiwan.

researchers from the Institute of Nutritional Science, Chung Shan Medical University, in Taiwan, conducted a placebo-controlled study with volunteers who consumed Konjac glucomannan progressively, and a 21-d Konjac glucomannan supplemented period (1.5 g/meal, 4.5 g/d). Eight healthy adults consumed 7-d cycle menus of typical low-fiber Chinese food throughout the study. The Konjac glucomannan supplement significantly increased the mean defecation frequency (number/day), wet stool weight, and dry stool weight. Konjac glucomannan significantly promoted the fecal concentrations of lactobacilli and total bacteria, and promoted the daily output of bifidobacteria, lactobacilli, and total bacteria. Konjac glucomannan supplement also promoted colonic fermentation. Supplementation of Konjac glucomannan into a low-fiber diet promoted the defecation frequency in healthy adults, by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation.

Glucomannan Beneficial for Cholesterol and Blood Lipids

Effect of plant sterols and glucomannan on lipids in individuals with and without type II diabetes.

Eur J Clin Nutr. 2006. School of Dietetics and Human Nutrition, McGill University, Montreal, Québec, Canada.

The purpose of this study was to determine whether supplements of plant sterols and/or glucomannan improve lipid profile and cholesterol biosynthesis in mildly type II diabetic and non-diabetic subjects with elevated cholesterol levesl. Subjects were supplemented with plant sterols (1.8 g/day), glucomannan (10 grams a day), a combination of glucomannan and plant sterols, and a placebo, provided in the form of bars.Overall plasma cholesterol concentrations were lowered after combination treatment compared to control. Plasma low-density lipoprotein (LDL) cholesterol concentrations were decreased after glucomannan and combination treatments compared to control. The results of lipid profiles did not differ between subject groups. The results suggest that glucomannan and a combination of glucomannan and plant sterols substantially improves plasma LDL cholesterol concentrations. No significant glucomannan side effects were reported.


Glucomannan comes from the Amorphophallus konjac plant but there are other sources, for instance glucomannan from Dioscorea esculenta tubers. Chemical analysis reveals that Aloe vera contains various carbohydrate polymers, notably glucomannans, along with a range of other organic and inorganic components.

Glucomannan Side Effects of Hepatitis

Acute hepatitis of cholestatic type possibly associated with the use of glucomannan (amorphophalus konjac).

J Hepatol. 2004. Villaverde AF, Benlloch S, Berenguer M, Miguel Rayón J, Pina R, Berenguer J.

Glucomannan and Ghrelin

Immediate and long-term effects of glucomannan on total ghrelin and leptin in type 2 diabetes mellitus.

Diabetes Res Clin Pract. 2009.

Effects of glucomannan as a supplementary treatment in type 2 diabetes mellitus were investigated by measuring ghrelin, leptin and insulin responses to OGTT. Glucomannan enhanced prandial ghrelin reduction when given before glucose load and impeded the rise of fasting ghrelin after 4-week supplement. Ghrelin-induced feeding may be attenuated by glucomannan.