Glucomannan

Glucomannan is a water-soluble polysaccharide composing 40% by dry weight of the roots or corm of the konjac plant. Glucomannan is a dietary fiber, and has been marketed as a treatment for constipation, obesity, high cholesterol, Acne vulgaris (source) and Type 2 diabetes. Glucomannan is also a hemicellulose that is present in large amounts in the wood of conifers and in smaller amounts in the wood of dicotyledons.

Constipation
Glucomannan is a soluble fiber, and as such, has been used in the treatment of constipation. Glucomannan may relieve constipation by decreasing fecal transit time (PMID 2547312). In the treatment of chronic constipation, glucomannan significantly improved symptoms of constipation while being well-tolerated and free of relevant side effects (PMID 1742540)

Obesity
Clinical evidence suggests glucomannan may be beneficial in weight loss (PMID 16320857). Because it is a soluble fiber, it absorbs water to form a viscous gel-like mass. This mass may promote feelings of satiety while traveling through the gastrointestinal tract. In obese patients, taking 1 gram of glucomannan with 8 ounces (250 ml) of water at 1 hour before each of 3 meals daily over 8 weeks resulted in an average weight loss of 5.5 pounds (2.5 kg) (PMID 6096282).

Cholesterol and other lipids
Glucomannan has demonstrated statistically significant improvements in the total cholesterol of obese patients, showing a mean weight loss of 5.5 pounds over 8 weeks (PMID 6096282). In healthy men, 4 weeks of taking 3.9 grams of glucomannan decreased total cholesterol, low-density lipoprotein, triglycerides, and systolic blood pressure; notably, triglycerides dropped by 23% (PMID 7872224). Glucomannan has also been tested in children with high cholesterol in conjunction with a diet. Interestingly, greater decreases in total cholesterol and low-density lipoprotein were observed in female children when compared to male children (PMID 15955465).

When used in conjunction with chitosan, glucomannan decreases serum cholesterol possibly by increasing steroid excretion via the feces (PMID 12356785).

Type 2 diabetes
Glucomannan may be useful as a therapeutic adjunct for Type 2 diabetes. It has been shown to improve the lipid profile and alleviate the fasting blood glucose levels of Type 2 diabetics (PMID 12569112).

Commercial use
As a food additive, glucomannan is used as an emulsifier and thickener. It has E number E425(ii). Glucomannan also makes up the majority of substance in shirataki noodles.

Glucomannane グルコマンナン