Konjac and glucomannan: Multi-purpose prebiotic fiber


When I was a kid, my mom would return from her occasional trips into New York City to buy food from a Japanese grocer with some konnyaku candy, a jelly-like sweet desert that came in large bars. I did not know then that this was a product made from konjac originating from an Asian yam. The dense candies have since been removed from the market, unfortunately, as some children choked on the thick jelly, casting a shadow over konjac products for a number of years. Concerns over other forms of the fiber have since been addressed and dismissed. (The solution is to sell the product in small bite-sized pieces, rather than large bars or other forms, or to chew the candy well. Glucomannan powder added to foods does not have this concern.)

But, consumed as a teaspoon of glucomannan powder (the dried powder of konjac) or as Shirataki noodles made from konjac, these foods provide a convenient way to increase intake of prebiotic fibers without the choking risk of the thick gelatin form. Konjac as a dried powder does indeed have substantial water-absorbing potential and has therefore been put to work in inducing satiety for weight loss purposes, as well as for increasing elimination of intestinal bile acids that leads to lower levels of total and LDL cholesterol. Clinical studies have therefore focused on weight loss and cholesterol-reducing effects (both of which are modest or minimal). But the prebiotic fiber properties of glucomannan are the most interesting.

Given prebiotic fiber content, konjac and glucomannan have been associated with:

      • Increased proliferation of probiotic Lactobacillus and Bifidobacteria species, while indirectly suppressing proliferation of Gram-negative pathogens and several Clostridia species. Short-chain fatty acids that both nourish the intestinal lining as well as mediate beneficial health effects (e.g., reduced insulin resistance, reduced blood sugar and blood pressure, reduced triglycerides) are also substantially increased.
      • Increased Bacteroidetes (away from the greater Firmicutes pattern seen in obesity and type 2 diabetes) and increased Akkermansia
      • Modest reductions in total and LDL cholesterol, but a more marked 23% reduction in triglycerides (the pattern often seen with prebiotic fiber supplementation).
      • Increased activity of an intestinal enzyme, alkaline phosphatase, that disables the lipopolysaccharide (LPS) of pathogenic bacterial species that is associated with endotoxemia. In other words, glucomannan likely reduces the severity of endotoxemia caused by dysbiosis and SIBO.

We do not, of course, confine intake of prebiotic fibers to only one source, but seek out variety: glucomannan/Shirataki, galactooligosaccharides from legumes, arabinogalactan and others from acacia fiber, inulin from onions, garlic, and asparagus, etc. Getting in a variety of prebiotic fibers helps cultivate bacterial species diversity in bowel flora, a powerful marker for overall health.

Knowing about glucomannan powder and Shirataki noodles therefore adds to the list of sources of prebiotic fibers that help cultivate bacterial species diversity. Glucomannan powder can be added to many dishes (add slowly and stir, as it can thicken your dish considerably; adding one teaspoon adds 4 grams prebiotic fiber to your daily intake) and is heat stable. Its moisture-absorbing properties can be put to use as a thickening agent, as well. If you are in the mood for an Asian-style dish, Shirataki noodles are a great choice. Here is my recipe for Ramen Noodles made with Shirataki noodles.


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