What is Glucomannan?
Weight Loss Supplement?
Often marketed for weight loss and type 2 diabetes, glucomannan (also know as “konjac”) is a root primarily composed of an indigestible fiber – which is why it can have a major laxative effect. While scarfing down this stuff in supplement form (it's currently available in tablet, capsule or powder forms) may help increase fullness and curb appetite, there are smarter and safer ways to do this.
Because of its inability to be absorbed, it may also reduce the absorption of much-needed fat-soluble vitamins A, D, E and K. When taken in combination with certain herbal supplements and diabetic medications, this supplement may also cause a dangerous drop in blood sugar.
Other safety risks include throat and gastrointestinal obstructions, so people that do choose to take this supplement are cautioned to use it in powdered or capsule form, instead of tablets.
You can also find glucomannan as the main ingredient in calorie-free pasta alternatives that are often referred to as “shirataki” noodles. Specific brands vary but typical ingredients are water, glucomann (sometimes listed as “yam flour”) and calcium hydroxide for its preservative value. One brand we came across also contained a tofu and had 20 calories per 4-ounce serving. A 3-ounce portion of the tofu-less varieties are listed as zero calories.
Noodles come packaged in fluid-filled sacs and some brands require refrigeration. The two brands we tried varied in price from about $1.50 to $3.00 for an 8-ounce package. The packing liquid has a distinctly awful fishy odor. While the stench does subside with rinsing, it lingers in your memory as you continue to prepare the noodles. A quick dunk in boiling water and they’re ready to eat. We tried them with traditional tomato sauce as well as stir-fried with soy and sriracha. While they’re virtually flavorless, there’s no escaping the unpleasant rubber-band-like texture.
Bottom Line: Indigestible substances don’t really count as food to me – especially when they’re tasteless with an unpleasant texture! As for the supplements, the dangers outweigh the benefits. Since potential dangers do exist, massive consumption of the noodle version should also be moderated.
Dana Angelo White, MS, RD, ATC, is a registered dietitian, certified athletic trainer and owner of Dana White Nutrition, Inc., which specializes in culinary and sports nutrition. See Dana's full bio »