Clayton's Health Facts: Glucomannan.

Clayton South, SPN (ISSA), is a recognized expert in the bodybuilding / fitness industry with over 150 bodybuilding, fitness and nutrition publications to his credit.
What is it and where does it come from?

Glucomannan is a water-soluble dietary fiber that's derived from the Konjac root (Amorphophallus konjac). Because glucomannan is found in negligible amounts in food, supplementation is necessary.

What does it do and what scientific studies give evidence to support this?

Glucomannan is a dietary fiber that helps to increase stool bulk by absorbing water. This helps stool pass more easily through the colon, preventing unnecessary stress to the colon and, in some cases, preventing injury to the colon tissues. When used to treat constipation, glucomannan delivers results (bowel movement) within twelve hours of administration.1 Glucomannan is an established and safe treatment option for constipation.2

Because it is a fiber, glucomannan can assist with weight loss and healthy weight maintenance by expanding in the stomach and absorbing fats. Absorbed fats are eliminated from the body and do not undergo digestion, thus nullifying their caloric effect. Also, glucomannan occupies space in the stomach and provides feelings of fullness. You'll eat less when this happens, and this will direct your body to tap into body fat stores for energy. Simply, you'll have a better chance of burning fat and losing weight when you use glucomannan. Research has shown that you can lose up to 5.5lbs in eight weeks without exercise by taking 1 gram of glucomannan with 250ml of water one-hour before each meal!

Using glucomannan may result in a lowering of your blood cholesterol.3 Numerous studies have confirmed that a lowering of LDL cholesterol (low density lipoproteins - the so-called "bad" cholesterol) and an increase in HDL cholesterol (high density lipoproteins - the so-called "good" cholesterol) is correlated strongly with glucomannan supplementation.4 This is welcome news if you suffer from, or are at risk for, hypertension or cardiovascular abnormalities.

Glucomannan can also help normalize blood sugar levels by delaying food digestion.5 Research has shown that this can help diabetics better control their response to food, easing the burden of dietary restrictions and making their diabetes more manageable.6

Glucomannan is a popular ingredient in nutritional weight-loss supplements because of its weight loss and insulin controlling abilities.

Who needs it and what are some symptoms of deficiency?

Glucomannan is not an essential nutrient and no daily requirement (RDA) exists. No symptoms of deficiency exist.

How much should be taken? Are there any side effects?

Frequent bowl movements are a side-effect of glucomannan at high doses (3-4 grams daily). Assess your tolerance to glucomannan by starting with a dose that is one-half of the recommended dose on the product label. Increase the dosage gradually, if you can tolerate this amount. Do not exceed the maximum dosage listed on the product label.

Do not use glucomannan if you have a disorder of the esophagus as the expanding fiber may act as an obstructing to breathing.

Consult with a physician before using any nutritional supplement.


  1. Marzio L, Del Bianco R, Donne M, et al. Mouth-to-cecum transit time in patients affected by chronic constipation: Effect of glucomannan. Am J Gastroenterol 1989;84:888-91.
  2. Marsicano LJ, Berrizbeitia ML, Mondelo A. Use of glucomannan dietary fiber in changes in intestinal habit G E N 1995;49:7-14 [in Spanish].
  3. Wu J, Peng SS. Comparison of hypolipidemic effect of refined konjac meal with several common dietary fibers and their mechanisms of action. Biomed Environ Sci 1997;10:27-37.
  4. Walsh DE, Yaghoubian V, Behforooz A. Effect of glucomannan on obese patients: a clinical study. Int J Obes 1984;8:289-93.
  5. Doi K. Effect of konjac fibre (glucomannan) on glucose and lipids. Eur J Clin Nutr 1995;49(Suppl. 3):S190-7 [review].
  6. Vorster HH, Lotter AP, Odendaal I, et al. Benefits from supplementation of the current recommended diabetic diet with gel fibre. Int Clin Nutr Rev 1988;8:140-6.