Glucomannan is a polysaccharide that is classified as a soluble fiber. Because glucomannan can absorb up to 200 times its weight in water, it has been used as a dietary supplement to promote weight loss (via increasing feelings of fullness). Glucomannan is derived from several plants, but the primary source is an Asian plant called Konjac.
Glucomannan Theory
Like many soluble fibers, glucomannan can bind with a variety of substances in the digestive tract to slow digestion, relieve constipation and reduce the absorption of fat and carbohydrates. As such, glucomannan is often used in products intended to reduce blood cholesterol and triglyceride levels as well as blood sugar. Because it can absorb a great deal of water and promote a feeling of fullness, glucomannan is frequently used in supplements intended to promote weight loss.
Glucomannan Scientific Support
A handful of clinical studies confirm that glucomannan lowers cholesterol (total and LDL). In childhood obesity, glucomannan has been shown to decrease cholesterol and triglyceride levels significantly.
In another study, 2 groups of 25 severely obese patients underwent very low calorie diet therapy for 3 months (with or without a 4 gram/day glucomannan supplement). The results showed that the glucomannan group had a significant loss of body weight and fat mass compared to the group receiving diet therapy alone. The glucomannan group also had a more pronounced change in lipid status and carbohydrate tolerance.
In another study, 20 obese subjects were given 1 gram of glucomannan with 8 ounces of water 1-hour prior to each meal for 2 months (versus a placebo). Subjects were instructed not to change their eating or exercise patterns. Results showed a significant weight loss (5.5 lbs) as well as a drop in serum levels of total and LDL cholesterol (15-20mg/dl) in the glucomannan group.
Glucomannan Safety
Like other soluble fibers, glucomannan has the potential to bind with and reduce the absorption of certain nutrients – so a daily multivitamin supplement may be advisable for individuals consuming high doses of glucomannan on a regular basis. In high doses, glucomannan may lead to diarrhea, bloating and flatulence – but cutting back the dose relieves these unpleasant side effects.
Glucomannan Dosage
Typical dosage recommendations for glucomannan are 1 gram consumed with at least 8 ounces of water approximately one hour prior to a meal (can be repeated 3-4 times per day at each meal). If combined with other fibers, follow the directions on the specific product because different fiber products may have different dosage/use recommendations.
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