Glucomannan (occasionally labeled as “konjac” or Amorphophallus konjac) is an un-absorbable polysaccharide that is derived from the konjac root. That’s a slightly complicated way of saying that glucomannan is a source of fiber.
Despite being the prime ingredient in several “less than credible” products (i.e., the makers of FiberThin, one glucomannan-based product, were recently sued by the Federal Trade Commission for making false and unsubstantiated claims about their product. Another product, Lipozene, has a hideous customer service record) glucomannan is a supplement worth investigating.
Of course, this should not come as a surprise—an increased fiber consumption has long been touted as a “low tech”, “low cost” diet strategy. Nancy Howarth, a nutritionist from Tuft’s University in Boston, suggests people who add an extra 14 grams per day to their diet could expect to lose 4 pounds and decrease food intake by 10% in 4 months.
Additionally, the typical low quality North American diet does not contain nearly enough fiber — the average North American consumes 15 grams of fiber daily—10 grams less than the minimum recommended amount of 25 mg.
So if your diet is lacking in fiber, glucomannan is certainly worthwhile investigating.
Best of all, there’s some decent clinical evidence validating its various benefits. For instance…
Several clinical studies validate glucomannan’s ability to lower LDL cholesterol, blood lipid levels and blood sugar levels (see J Am Coll Nutr. 2003 Feb;22(1):36-42, Diabetes Care. 2000 Jan;23(1):9-14, Nutr Metab Cardiovasc Dis. 2005 Jun;15(3):174-80, Diabetes Care. 1999 Jun;22(6):913-9, Biomed Environ Sci. 1990 Jun;3(2):123-31). It appears to be especially useful for diabetics in this regard.
One study (Int J Obes. 1984;8(4):289-93) showed that 1 gram of glucomannan, taken with 8 oz. of water one hour prior to meals, has a significant influence on weight loss—almost 6 pounds of fat lost in two months, with no changes in eating habits.
It should be noted that this equates to .75 lbs. of weight per week… hardly on “par” with the sort of results promised by the retailers of the more outrageous glucommannan-based weight loss products.
This study “Glucomannan and obesity: a critical review” concluded…
“At doses of 2-4 g per day, GM was well-tolerated and resulted in significant weight loss in overweight and obese individuals. There is some evidence that GM exerts its beneficial effects by promoting satiety and fecal energy loss. Additionally, GM has been shown to improve lipid and lipoprotein parameters and glycemic status.”
A more recent study (see J Am Coll Nutr. 2007 Dec;26(6):663-8) showed glucomannan may play a role in the treatment of hyperthyroidism. It’s been shown to be helpful in the treatment of childhood constipation as well (see Pediatrics. 2004 Mar;113(3 Pt 1):e259-64).
Despite what appears to be mounds of positive evidence, there are a couple of issues with glucomannan.
First, glucomannan may bind with and hinder the absorption of certain nutrients. It’s probably a good idea to use a high quality multi-vitamin when supplementing with glucomannan or glucomannan-based products, and to consume that later in the day, either prior or sometime after you’ve consumed this supplement.
Secondly, I’ve received some interesting feedback regarding glucomannan-based products and their side effects.
This feedback seems to indicate that glucomannan pills can occasionally get stuck in the esophagus and cause a blockage.
Although this seems a bit far-fetched, a clinical study (Clin Toxicol (Phila). 2007;45(1):80-2) indicates that glucomannan-based supplements can pose a hazard for individuals with upper gastrointestinal pathology.
One way to avoid this issue is break open the capsules and sprinkle it over your food.
Bottom line on glucomannan?
It’s a convenient form of fiber that appears to have plenty of benefits. Although you can get more fiber into your diet simply by eating the right fruits and vegetables, many people will appreciate the simplicity offered by glucomannan capsules. It will likely help you eat less, and this reduction in calories may cause you lose weight. Remember though, the results are subtle at best. This isn’t a “10 lbs. in 10 days” solution.
If you’re interested in experimenting with this supplement, stay away from high-priced, specialty diet products. The NOW brand Glucomannan supplement is a suitable alternative, and it’s cheap; a 180-capsule bottle is just under $10 at BodyBuilding.com, our recommended online retailer. At this price, it’s well worth experimenting with!