Glucomannan konjac supplement benefit for cholesterol, diabetes, and constipation, Amorphophallus konjac

Glucomannan is a water-soluble polysaccharide dietary fiber. It is also a food additive used as an emulsifier and thickener. The botanical name is Amorphophallus konjac.

Glucomman supplement product
This supplement is gaining popularity and consumers realize many health benefits it offers. Products containing glucomanan, marketed under a variety of brand names, are sold as dietary supplements for constipation, obesity, high cholesterol, and type 2 diabetes. Here are some examples of products you can find over the counter:

Glucomannan (root) - 500 mg per capsule
Glucomannan (root) - 600 mg per capsule

Human studies with glucomannan konjac supplement
There have been many human studies evaluating the benefit of glucomannan on blood lipids, body weight, fasting blood glucose, and blood pressure. Most of the clinical trial show glucomannan lowered total cholesterol, LDL cholesterol, triglycerides, body weight, and fasting blood glucose. Glucomannan has a role to play in clinical medicine in terms of reducing total cholesterol, LDL cholesterol, triglycerides, fasting blood sugar, and perhaps body weight, but does not seem to have much of an effect on HDL cholesterol or blood pressure.

Bower function and constipation
Supplementation with glucomannan in those with a low fiber diet promotes defecation frequency, possibly by increasing the stool bulk, thus promoting the growth of lactic acid bacteria and colonic fermentation.

Supplementation of konjac glucomannan into a low-fiber Chinese diet promoted bowel movement and improved colonic ecology in constipated adults: a placebo-controlled, diet-controlled trial.
J Am Coll Nutr. 2008 Feb; Institute of Nutritional Science, Chung Shan Medical University, Taichung, Taiwan 402.
This diet-controlled study was designed to examine effects of konjac glucomannan supplement on the bowel habits and colonic ecology in 7 constipated subjects. Seven constipated subjects who passed bowel movement less than once a day participated in this diet-controlled linear study that consisted of a 21-d placebo period, a 7-d adaptation period, and a 21-d konjac glucomannan-supplemented (1.5 g, three times a day) period. The large bowel response and fecal characteristics were recorded daily. KGM supplement slightly but significantly increased the weekly defecation frequency from 4 to 5.3 and slightly eased the bowel movement. The fecal wet weight (g/d) and percent moisture were not significantly altered with the fiber supplement. However, the dry fecal weight (g/d) was increased mainly in the soluble mass. Konjac glucomannan supplement increased the fecal concentration of lactobacilli, and the daily output of bifidobacteria, lactobacilli and total bacteria in this diet-controlled study. In addition, fermentation of konjac glucomannan resulted in greater fecal acetate, propionate and i-butyrate concentrations and lower fecal pH. The modest dose of konjac glucomannan supplement promoted bowel movement by 30% and improved colonic ecology in constipated adults.

Cholesterol reduction
Evaluation of the pharmacotherapeutic efficacy of Garcinia cambogia plus Amorphophallus konjac for the treatment of obesity.
Phytother Res. 2008 Sep; Vasques CA, Rossetto S, Halmenschlager G, Linden R, Heckler E, Fernandez MS, Alonso JL. Instituto de Ciências da Saúde, Ciências Farmacêuticas, Centro Universitário Feevale, RS-239, 2755, 93352-000 Novo Hamburgo-RS, Brazil.
Hydroxycitric acid (HCA), the main compound of Garcinia cambogia extract, is a competitive blocker of ATP-citrate-lyase, presenting a potential inhibition of fatty acid biosynthesis. Glucomannan fibers, abundant in Amorphophallus konjac, seem to reduce the absorption kinetics of dietary fat. Therefore, the aim of this double-blind randomized study was to evaluate the efficacy of standardized extracts of G. cambogia (52% HCA) plus A. konjac (94% glucomannan) in the treatment of obesity. Fifty-eight obese subjects were assigned to the placebo group or the treatment group; no dietary restrictions were applied. Over a 12-week period, subjects were given daily doses of either Garcinia (2.4 g) plus Konjac (1.5 g) or placebo prior to their main meals (3 times/day). Before the start of treatment, and every 4 weeks thereafter, the following were recorded: height, weight, circumferences and body composition, resting energy expenditure, lipid profile and glucose levels. The treatment had no significant effect on anthropometric parameters, resting energy expenditure, triglycerides or glucose levels. However, a significant reduction was observed in total cholesterol and LDL-c levels in the treated group, the final levels being significantly lower than those of the placebo group. The results obtained suggest that the treatment had a significant cholesterol lowering effect, without influencing the anthropometric or calorimetric parameters tested.

Cholesterol reduction in children
Effect of dietary supplementation with glucomannan on plasma total cholesterol and low density lipoprotein cholesterol in hypercholesterolemic children.
Nutr Metab Cardiovasc Dis. 2005 June; Martino F, Martino E, Morrone F, Carnevali E, Forcone R, Niglio T. Lipid Clinic Research, Istituto di Clinica Pediatrica, Università di Roma La Sapienza, Viale Regina Elena 324, I-00161 Roma, Italy.
This paper evaluates the effect of the adjunct of the hydrosoluble fiber glucomannan to a Step-One-Diet in 40 plasma hypercholesterolemic children, during a randomized controlled trial, to reduce plasma cholesterol. All the subjects recruited underwent an 8-week run in diet period; a Step-One-Diet was prescribed. After that, they were randomly allocated to one of two groups: Step-One-Diet only (control), and Step-One-Diet plus glucomannan in gelatine capsules. After another 8 weeks of treatment, the results were compared within and between the two groups. Glucomannan treated group showed decreased values in plasma total cholesterol and low density lipoprotein cholesterol vs. control group after 8 weeks of treatment. Our results suggest that glucomannan may represent a rationale adjunct to diet therapy in primary prevention in high risk children with elevated cholesterol levels.

Diabetes
Glycemic and lipid responses to glucomannan in Thais with type 2 diabetes mellitus.
J Med Assoc Thai. 2007 Oct; Chearskul S, Sangurai S, Nitiyanant W, Kriengsinyos W, Kooptiwut S, Harindhanavudhi T. Department of Physiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
To evaluate the benefits of glucomannan supplement on glycemic and lipid controls in type 2 diabetic patients. A single-blind, placebo-controlled, crossover trial with two treatments separated by a 2-week washout period was performed in 10 men and 10 women with type 2 diabetes mellitus. Two separated protocols of experiments were sequentially followed. Initially, purified glucomannan (1 g) or placebo was ingested 30 min before 75-g glucose load to evaluate their effects on glucose absorption and insulin secretion in oral glucose tolerance test (OGTT). Later, the glycemic and lipid changes after 4-week intervention with 3 g/day glucomannan comparing to the placebo were determined. Glucomannan taken before performing the OGTT can lower the rise of blood glucose and insulin from 1 to 2 hour in comparison with the placebo, though a statistically significance of insulin was not achieved. Long-term glucomannan supplement significantly reduced the 120-min glucose area under the curve of OGTT. Glucomannan also decreased the rise of low-density lipoprotein cholesterol (LDL-C). In type 2 diabetes, pre-prandial glucomannan ingestion attenuated a rise of blood glucose without significantly affecting insulin levels. Long-term supplement of glucomannan to the regular diabetic regimen lessened post challenge glucose AUC and impeded the rise of LDL-C. Supplement of glucomannan may be beneficial to the glycemic and lipid controls in type 2 diabetes mellitus.

Thyroid gland
The use of konjac glucomannan to lower serum thyroid hormones in hyperthyroidism.
J Am Coll Nutr. 2007 Dec; Azezli AD, Bayraktaroglu T, Orhan Y. Istanbul University, Istanbul Faculty of Medicine, Department of Internal Medicine, Division of Endocrinology Metabolism and Nutrition, Fatih-Istanbul, Turkey.
Patients with hyperthyroidism occasionally need rapid restoration to the euthyroid state. In view of the increased enterohepatic circulation of thyroxine (T4) and triiodothyronine (T3) in thyrotoxicosis, and metabolic effects of konjac glucomannan in gastrointestinal system, we aimed to determine the activity of glucomannan in treatment of hyperthyroidism. A prospective, randomized, placebo-controlled, one-blind study design was used with newly diagnosed 48 hyperthyroid patients (30 patients with Graves' disease and 12 with multinodulary goitre). They were assigned to one of the following treatment groups: I) methimazole 2 x 10 mg, propranolol 2 x 20 mg, and glucomannan (Propol) 2 x 1.3 gr daily for two months; II) methimazole 2 x 10 mg, propranolol 2 x 20 mg, and placebo powder daily for two months. No differences were detected from the point of view of the baseline thyroid hormone levels between groups. Further analyses revealed that the patients receiving glucomannan at the end of the second, fourth and sixth weeks of the study had significantly lower serum T3, T4, FT3 and FT4 levels than the patients who received placebo. TSH was not different between the two groups at any specific time. At week 8, thyroid hormone levels were not shown any differences. The glucomannan-treated group had a more rapid decline in all four serum thyroid hormone levels than the placebo-treated group. We believe our preliminary results indicate that glucomannan may be a safe and easily tolerated adjunctive therapeutic agent in the treatment of thyrotoxicosis. This combination therapy seems most effect during first weeks of treatment of a hyperthyroid patient.