Scientific Name s : Amorphophallus konjac Koch. Common Name s : Glucomannan, Gonyak, Konjac, Konjac mannan, Konnyaku Clinical Overview Use Glucomannan has been investigated for its effects on weight reduction, diabetes, constipation, cholesterol, lung cancer, and atopic diseases, as well as its use as a prebiotic. There are issues of quality concerning the evidence to support use for these indications. Dosing Clinical studies of glucomannan in diabetes, cholesterol control, and obesity have used dosages of 1 to 13 g daily.

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Scientific Name s : Amorphophallus konjac Koch. Common Name s : Glucomannan, Gonyak, Konjac, Konjac mannan, Konnyaku Clinical Overview Use Glucomannan has been investigated for its effects on weight reduction, diabetes, constipation, cholesterol, lung cancer, and atopic diseases, as well as its use as a prebiotic.

There are issues of quality concerning the evidence to support use for these indications. Dosing Clinical studies of glucomannan in diabetes, cholesterol control, and obesity have used dosages of 1 to 13 g daily.

Contraindications Given the risk of esophageal and gastric obstruction, use is not recommended in patients with structural abnormalities of the esophagus or gut.

Until more information is obtained, use is not recommended in pregnant or breast-feeding women. Additionally, glucomannan may reduce the bioavailability of other oral medications. Thus, it is recommended that other medications be taken 1 hour before or 4 hours after glucomannan administration. Adverse Reactions Severe esophageal and GI obstruction have been reported with glucomannan tablets. The hypoglycemic effects are potentially dangerous to patients with diabetes.

Glucomannan has been linked in case reports to cholestatic hepatitis and occupational asthma. Minor adverse effects are normally GI related and include diarrhea, flatulence, abdominal discomfort, and bloating. Data suggest diarrhea, abdominal pain, and flatulence occur with dosages more than 5 g daily.

Scientific Family Araceae Source Konjac mannan is a polysaccharide derived from the tubers or roots of the elephant yam or konjac. Konjac flour has been traditionally produced through processing corms, the underground storage organs. After boiling with plant ash, the flour is consumed as cake or gel. Chinese people have used konjac glucomannan for over 2, years to treat conditions such as asthma, cough, hernia, breast pain, burns, and hematological and skin diseases.

The leaves have also been used as an insect repellent. In the 6th century AD, konjac glucomannan was introduced to Japan as a medicinal product. It has been approved by the Food and Drug Administration FDA since as a food additive and since as a binder in meat products.

China is the largest producer of konjac, and Japan is the second largest. In China, approximately factories manufacture konjac flour. The dry formulation swells into a viscous gel in hot or cold water, absorbing up to 50 times its weight when in water.

Glucomannan was once believed to be nonbiodegradable; however, certain gut flora bacteria such as Aerobacter mannaolyticus, Clostridium butyricum, and Clostridium beijerinckii contain endo-beta-mannanases that catalyze the degradation of glucomannan into disaccharides and eventually to glucose and mannose. In Japan, this coagulated product is called "konnyaku" and is commonly used as a foodstuff.

In Korea, it is referred to as "gonyak. Fresh corms contain organic compounds, including beta-carotene, choline, niacin, riboflavin, and thiamine. In addition, serotonin and its derivatives have been found in fresh corms. Their ability to swell by the absorption of water has made them useful as laxatives. Additionally, konjac glucomannan has been investigated for its role as a prebiotic, an agent that stimulates the growth and activity of beneficial gut flora, including Bifidobacterium and Lactobacillus species.

Research on microflora in mice and rats suggests a diet that includes konjac mannan alters microbial metabolism in the intestine. Of note, glucomannan hydrolysate had a 2- to 4-fold larger anaerobe count at 4 weeks compared with unhydrolyzed glucomannan and cellulose treatment groups.

Both unhydrolyzed glucomannan and glucomannan hydrolysate decreased cecal Clostridium perfringens, a potentially harmful bacterium, at week 4. Both of these compounds modulated fecal and cecal flora in a dose-dependent fashion.

The compound was also able to decrease counts of fecal Escherichia coli and C. Eight adult volunteers 21 to 54 years of age followed the study design of 3 weeks of placebo and 1 week of adaptation in which konjac glucomannan was titrated from 1. On days 15 to 21 of the placebo and treatment periods, all stools were collected. Diet was controlled by having the patients adhere to a 7-day cycle menu, consisting of various low-fiber Chinese foods throughout the entire study.

Supplementation did not cause abdominal cramping, bloating, or flatulence. Supplementation with konjac glucomannan led to an increase in defecation each week 4.

The fecal weight wet was not impacted by fiber supplementation, while the fecal dry weight was increased. Supplementation also increased the fecal output of bifidobacteria, lactobacilli, and total bacteria.

Each patient received glucomannan or placebo for 4 weeks and then the other treatment for 4 weeks. No side effects were reported by the participants. There was no significant difference between glucomannan and placebo groups in response to constipation, defined as 3 or more stools per week without soiling.

Adverse event rates, and use of rescue medication lactulose were similar between groups. This likely improves peripheral insulin sensitivity. Only 1 of the fractions, KOS-A, at concentrations of less than 1.

Additionally, at this concentration, KOS-A did not alter normal insulin secretion. When 13 diabetic patients received 3. The polysaccharide reduced mean blood glucose levels by 7. Another study of 72 type 2 diabetic patients showed a reduction in fasting blood glucose and postprandial blood glucose after consuming konjac food 30 and 65 days. However, this reduction was not statistically significant when compared with a standard glucose load or white rice load. The polysaccharide is believed to cause weight loss by promoting satiety, delaying gastric emptying time, slowing small-bowel transit time, attenuating postprandial insulin surges, and increasing levels of plasma cholecystokinin.

Clinical data Konjac mannan is often included in "grapefruit diet" tablets. One US patent claims that its use resulted in weight loss without appetite changes; however, no weights were reported. Some research has indicated that patients treated with oral glucomannan have decreased body weight compared with control groups.

In 1 study involving an 8-week cardiac rehabilitation program, patients were given 1. These losses were significant when compared with the placebo group. Cholesterol parameters also improved. Research conducted in 60 children younger than 15 years mean age, Similarly, 30 children received placebo and the mean weight decreased from However, there were no statistically significant differences between the treatment and placebo groups.

The authors cited flaws in published studies including insufficient detail on randomization concealment methods and brief study duration just 3 weeks for 2 of the included studies. A novel polysaccharide, PolyGlycopleX or PGX, has been developed by reacting glucomannan with various polysaccharides. This new compound possesses the highest viscosity and water-holding properties compared with other fibers.

Specifically, women experienced an average weight loss of 5. Total cholesterol, LDL-C, and fasting blood glucose levels were also reduced. Rather, it appears to inhibit the active transport of cholesterol in the jejunum and the absorption of bile acids in the ileum, yielding improvements in plasma LDL and apolipoprotein B levels. The hypocholesteremic effect is completely eliminated when the mannan is coagulated to a water-insoluble form. Rats treated with konjac mannan that had been coagulated with cellulase had mean cholesterol levels greater than the controls.

The implication is that the foodstuff konnyaku coagulated water-insoluble product most likely has no cholesterol-reducing activity. Several other studies confirm the effects of konjac mannan on lipid metabolism. No differences were noted between groups. Additionally, this study also determined that glucomannan reduced body weight, percent body fat, systolic blood pressure, waist circumference, and glucose levels.

However, HDL and blood pressure were not affected by glucomannan therapy. In a clinical study of 40 children with hypercholesterolemia, patients underwent a 1-week diet run-in phase followed by randomization to either glucomannan 1 to 1. Treatment with glucomannan was associated with a significant reduction in total cholesterol and LDL cholesterol values from baseline compared with the control group.

The study reported no adverse reactions to the konjaku powder. Scratching behaviors and skin severity scores were reduced in those mice fed glucomannan in a dose-dependent fashion. The mice receiving placebo experienced an increase in this behavior. The mice that continued to receive glucomannan experienced an inhibition of eosinophilia and hyperkeratosis. Other uses In a prospective, randomized, placebo-controlled study, 48 newly diagnosed hyperthyroid patients were randomized to receive treatment with methimazole and propranolol plus glucomannan 1.

Hormone levels more rapidly declined in patients receiving glucomannan. Thyroid stimulating hormone levels were suppressed in both groups at weeks 2, 4, and 6; however, it normalized after 8 weeks of treatment in patients receiving glucomannan. At the end of 8 weeks of treatment, these levels were not different between groups.

Thus, glucomannan may have a role in the initial treatment of patients with hyperthyroidism to rapidly lower thyroid hormone levels. Specifically, sneezing was reduced in mice receiving glucomannan compared with controls.

Additionally, supplementation with konjac glucomannan reduced total immunoglobulin E concentrations. This allows for a lower dosage of the konjac glucomannan solution to be infused. Also, glucomannan has been combined with other polysaccharides including carrageenan, xanthan, acetan, gellam gum, alginate, and chitosan to improve gelling properties as part of drug delivery applications.

Until more information is known, use is not recommended in pregnant or breast-feeding women. Interactions Given the possibility of reducing blood glucose levels, caution should be used in patients receiving oral hypoglycemic agents, insulin, or alternative medicines that lower glucose levels.

Thus, it is recommended to take other medications 1 hour before or 4 hours after glucomannan administration. Four of these obstructions occurred in the proximal one-third of the esophagus. One patient developed mediastinitis due to perforation of the esophagus. Glucomannan-containing tablets have been banned in Australia since May because these also carry the potential for inducing lower GI obstruction.

Encapsulated and powder forms remain available. Glucomannan use is associated with a reduction in the need for hypoglycemic agents, and the product may result in a loss of glycemic control in patients with diabetes.


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