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What is Glucomannan?

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Glucomannan AKA elephant yam

Glucomannan is a substance derived from the roots of the Amorphophallus konjac plant, also known as the elephant yam. The plant, which is native to east Asia, has been appreciated in China for over two millennia as nutritional support for the respiratory system, breast health, burns, skin disorders, and detoxification. Only in the last twenty years has konjac powder become available in the United States and Europe as a dietary supplement — most commonly in capsules or as a drink mix. In that time, numerous clinical studies have evaluated glucomannan for its effects on constipation, weight loss, cholesterol, blood sugar, and colon health. [1]

Glucomannan for Constipation

Glucomannan is a soluble fiber and often cited as a remedy for constipation. In the digestive system, glucomannan absorbs water and forms a mass that promotes a bowel movement — in this respect it’s very similar to a bulk forming laxative. Now, the main selling point of glucomannan is that it has the highest water-holding capacity of all dietary fiber. Glucomannan has the added bonus in that not only does it increase stool bulk, it also promotes a healthy environment in the gut by supporting the growth of friendly intestinal flora. [2] [3] However, before we declare glucomannan the heavy-weight champion of constipation relief, it’s important to remember that glucomannan is the most fibrous of fibers, and even more prone to the negative effects that bulk-forming fiber can produce — including flatulence, gas, bloating, abdominal discomfort, and even obstruction. [4]

Should Constipated Children Take Glucomannan?

Glucomannan has produced mixed results for remedying constipation in children. Some research has found glucomannan to be beneficial if the children are already taking laxatives. [5] However, the results of a 2011 study stated that glucomannan was no more effective than placebo. [6] But, then again, an Italian study reported glucomannan to be very effective for increasing bowel movement frequency in children with severe brain damage — a group especially prone to constipation. [7] Overall, it seems that the argument may be there, but the verdict is inconclusive.

Glucomannan for Obesity and Weight Loss

Glucomannan has received attention for its potential to support healthy body weight. Although some of this has to do with its effect on blood sugar, most of the assertion is because glucomannan is extremely satient, meaning that consuming it will make you feel full — and, ideally, it can be used as a tool to reduce food intake. [8] More than one clinical trial has shown that consuming glucomannan before a meal may help reduce the amount of food consumed during the meal. [9] [10]

However, researchers at Harvard Medical School advise caution when looking to glucomannan for weight loss. First, it doesn’t always produce positive results. Additionally, the discouraging reality is that most weight loss products are purchased by those hoping for fast, low-effort results and many people do not make diet or lifestyle adjustments. [11] [12] This is important to note, especially since glucomannan is most effective when used in conjunction with a healthy diet and regular exercise. [13]

It also deserves mention that some of the companies that sell glucomannan promote unrealistic expectations. Some have even taken the liberty of calling glucomannan a fat burner. This is a big stretch of the imagination. Although dietary fiber does tend to increase metabolic heat after eating, the effect is brief and has very little effect. [14] Let’s not mince words, if you’re hoping that glucomannan will melt away the pounds like an ice cube in the desert, you will be disappointed.

Glucomannan and Childhood Obesity

Childhood obesity is an all-too-common pediatric disorder with many causes, and finding the right magic potion is not my idea of the best solution. Childhood is a time when establishing good, healthy lifestyle habits is paramount. Healthy habits, specifically a healthy diet and regular exercise, are the cornerstone for promoting a life-long healthy body weight. [15] Additionally, glucomannan doesn’t produce consistent results for obese children. There are some mildly encouraging reports floating around and others that are not. [16] [17] Recently, a double-blind, clinical investigation into the therapeutic potential of glucomannan for overweight children found it to be no more effective than placebo. [18]

Glucomannan and Cholesterol

One interesting, health promoting quality of glucomannan is that evidence seems to suggest it promotes normal blood lipid profiles. [19] A few years ago, a double-blind Swedish study reported that healthy adult men who consumed glucomannan were more likely to have favorable cholesterol levels. [20]

Support for giving glucomannan to children at risk for high cholesterol has been less enthusiastic. Although some positive experiences exist, researchers at the University of Connecticut School of Medicine reviewed available data and reported that most results were inconsistent and inconclusive. [21] [22]

Other Potential Benefits of Glucomannan

The scientific inquiries into the capacities of glucomannan are not limited to bowel movements or weight loss and are, in fact, somewhat diverse.

  1. Acne Remedy — Although the status of this one is early, it seems that the probiotic bacteria strains that inhibit the growth of acne are given a boost when glucomannan is present. [23]
  2. Vaginal Health — Somewhat similarly, a study last year found that glucomannan promotes a healthy ecology in the vagina by encouraging the presence of friendly flora. [24]
  3. Thyroid Support — Hyperthyroidism is a condition in which the thyroid gland is too active and overproduces hormones. One study found that glucomannan promoted a decline in hormone levels in persons with hyperthyroidism. [25] Although the research is very preliminary, it raises the question — does glucomannan affect the hormone levels of persons with normal thyroid function?
  4. Liver Support? — Glucomannan’s bulk-producing behavior in the digestive tract has an added feature, it can slow carbohydrate absorption. Reduced carbohydrate absorption means a reduced insulin response — something that has been linked to favorable liver function. [26]

Should You Take Glucomannan?

Undeniably, in the world of dietary fiber, glucomannan is a heavy hitter. There is no denying that it may increase feelings of fullness — in the right hands, this could be an effective weight loss tool. It also absolutely increases stool bulk — if you can’t go to the bathroom, it is possible that glucomannan may have something to offer. There’s also a reasonable argument that it may encourage normal lipid profiles and even offer a few other benefits.

However, it is also undeniable that at its base, glucomannan is a very aggressive dietary fiber that may cause obstruction, bloating, abdominal discomfort, and flatulence. The source of glucomannan must also be considered. Is it organic? Is it free of pesticides, pollution, metals, and toxins? It’s one thing to think so, it’s another to know so.

I do not take glucomannan because there are better options for managing constipation and weight loss. If you have experience taking it, however, please weigh in and leave a comment! What results did you notice? Do you still take it?

-Dr. Edward F. Group III, DC, ND, DACBN, DABFM


  1. Chua M, Baldwin TC, Hocking TJ, Chan K. Traditional uses and potential health benefits of Amorphophallus konjac K. Koch ex N.E.Br. J Ethnopharmacol. 2010 Mar 24;128(2):268-78. doi: 10.1016/j.jep.2010.01.021. Epub 2010 Jan 15.
  2. Chen HL, Cheng HC, Liu YJ, Liu SY, Wu WT. Konjac acts as a natural laxative by increasing stool bulk and improving colonic ecology in healthy adults. Nutrition. 2006 Nov-Dec;22(11-12):1112-9. Epub 2006 Oct 4.
  3. Chiu YT, Stewart M. Comparison of konjac glucomannan digestibility and fermentability with other dietary fibers in vitro. J Med Food. 2012 Feb;15(2):120-5. doi: 10.1089/jmf.2011.0084. Epub 2011 Dec 8.
  4. González Canga A, Fernández Martínez N, Sahagún AM, García Vieitez JJ, Díez Liébana MJ, Calle Pardo AP, Castro Robles LJ, Sierra Vega M. [Glucomannan: properties and therapeutic applications]. Nutr Hosp. 2004 Jan-Feb;19(1):45-50.
  5. Loening-Baucke V, Miele E, Staiano A. Fiber (glucomannan) is beneficial in the treatment of childhood constipation. Pediatrics. 2004 Mar;113(3 Pt 1):e259-64.
  6. Chmielewska A, Horvath A, Dziechciarz P, Szajewska H. Glucomannan is not effective for the treatment of functional constipation in children: a double-blind, placebo-controlled, randomized trial. Clin Nutr. 2011 Aug;30(4):462-8. doi: 10.1016/j.clnu.2011.01.012. Epub 2011 Feb 12.
  7. Staiano A, Simeone D, Del Giudice E, Miele E, Tozzi A, Toraldo C. Effect of the dietary fiber glucomannan on chronic constipation in neurologically impaired children. J Pediatr. 2000 Jan;136(1):41-5.
  8. Keithley J, Swanson B. Glucomannan and obesity: a critical review. Altern Ther Health Med. 2005 Nov-Dec;11(6):30-4.
  9. Vuksan V, Panahi S, Lyon M, Rogovik AL, Jenkins AL, Leiter LA. Viscosity of fiber preloads affects food intake in adolescents. Nutr Metab Cardiovasc Dis. 2009 Sep;19(7):498-503. doi: 10.1016/j.numecd.2008.09.006. Epub 2009 Jan 21.
  10. Vita PM, Restelli A, Caspani P, Klinger R. [Chronic use of glucomannan in the dietary treatment of severe obesity]. Minerva Med. 1992 Mar;83(3):135-9.
  11. Saper RB, Eisenberg DM, Phillips RS. Common dietary supplements for weight loss. Am Fam Physician. 2004 Nov 1;70(9):1731-8.
  12. Pittler MH, Ernst E. Dietary supplements for body-weight reduction: a systematic review. Am J Clin Nutr. 2004 Apr;79(4):529-36.
  13. Kraemer WJ, Vingren JL, Silvestre R, Spiering BA, Hatfield DL, Ho JY, Fragala MS, Maresh CM, Volek JS. Effect of adding exercise to a diet containing glucomannan. Metabolism. 2007 Aug;56(8):1149-58.
  14. Scalfi L, Coltorti A, D’Arrigo E, Carandente V, Mazzacano C, Di Palo M, Contaldo F. Effect of dietary fibre on postprandial thermogenesis. Int J Obes. 1987;11 Suppl 1:95-9.
  15. Rogovik AL, Chanoine JP, Goldman RD. Pharmacotherapy and weight-loss supplements for treatment of paediatric obesity. Drugs. 2010 Feb 12;70(3):335-46. doi: 10.2165/11319210-000000000-00000.
  16. Livieri C, Novazi F, Lorini R. [The use of highly purified glucomannan-based fibers in childhood obesity]. Pediatr Med Chir. 1992 Mar-Apr;14(2):195-8.
  17. Walsh DE, Yaghoubian V, Behforooz A. Effect of glucomannan on obese patients: a clinical study. Int J Obes. 1984;8(4):289-93.
  18. Vido L, Facchin P, Antonello I, Gobber D, Rigon F. Childhood obesity treatment: double blinded trial on dietary fibres (glucomannan) versus placebo. Padiatr Padol. 1993;28(5):133-6.
  19. Vuksan V, Jenkins DJ, Spadafora P, Sievenpiper JL, Owen R, Vidgen E, Brighenti F, Josse R, Leiter LA, Bruce-Thompson C. Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial. Diabetes Care. 1999 Jun;22(6):913-9.
  20. Arvill A, Bodin L. Effect of short-term ingestion of konjac glucomannan on serum cholesterol in healthy men. Am J Clin Nutr. 1995 Mar;61(3):585-9.
  21. Martino F, Martino E, Morrone F, Carnevali E, Forcone R, Niglio T. Effect of dietary supplementation with glucomannan on plasma total cholesterol and low density lipoprotein cholesterol in hypercholesterolemic children. Nutr Metab Cardiovasc Dis. 2005 Jun;15(3):174-80.
  22. Sood N, Baker WL, Coleman CI. Effect of glucomannan on plasma lipid and glucose concentrations, body weight, and blood pressure: systematic review and meta-analysis. Am J Clin Nutr. 2008 Oct;88(4):1167-75.
  23. Al-Ghazzewi FH, Tester RF. Effect of konjac glucomannan hydrolysates and probiotics on the growth of the skin bacterium Propionibacterium acnes in vitro. Int J Cosmet Sci. 2010 Apr;32(2):139-42. doi: 10.1111/j.1468-2494.2009.00555.x. Epub 2009 Oct 10.
  24. Tester R, Al-Ghazzewi F, Shen N, Chen Z, Chen F, Yang J, Zhang D, Tang M. The use of konjac glucomannan hydrolysates to recover healthy microbiota in infected vaginas treated with an antifungal agent. Benef Microbes. 2012 Mar 1;3(1):61-6. doi: 10.3920/BM2011.0021.
  25. Azezli AD, Bayraktaroglu T, Orhan Y. The use of konjac glucomannan to lower serum thyroid hormones in hyperthyroidism. J Am Coll Nutr. 2007 Dec;26(6):663-8.
  26. McCarty MF. Glucomannan minimizes the postprandial insulin surge: a potential adjuvant for hepatothermic therapy. Med Hypotheses. 2002 Jun;58(6):487-90.

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