Konjac is an herb with a tuber-like corm (underground plant stem). It’s also known as elephant yam, devil’s tongue, snake palm, and voodoo lily. Overall, konjac is highly versatile in a number of products and dishes notwithstanding its Japanese cuisine roots. Let’s explore – what the heck is konjac?
Konjac is high in a soluble fibre called glucomannan which gives it gelatinous properties. Konjac can be used to make flour, jelly, and fibre supplements. A popular use is to make noodles. The most common are Japanese noodles, created using konjac glucomannan flour, which are called shirataki and Ito-konnyaku. The flavour of shirataki noodles is fairly bland, but Ito-konnyaku uses algae to improve its flavour (3). Noodles made from konjac are often calorie-free and marketed to dieters. However, traditionally they are used in stir-fries, and hot pot. It is also used as a jell component in lychee jelly cups, and it is used as an ingredient found in chewing gum.
Konjac and Health
The top three potential health benefits of Konjac are digestive health, heart health, and weight loss. These benefits can be attributed to its high soluble fibre content.
Konjac’s fibre glucomannan has been shown to reduce constipation. A study conducted on seven constipated adults using a 21-day placebo, a seven day adaption period, a 21-day test period using a konjac glucomannan supplement of 1.5 g three times per day, found that bowel movements improved by 30% in constipated participants (1).
A systematic review and meta-analysis on three randomized control trials conducted on 122 children in total found that an increase in bowel movements with the supplementation of glucomannan (2). Overall, konjac shows promising effects on constipation; however, more research is required to analyze long term effects of konjac glucomannan on constipation prevention.
Cholesterol reduction is a potential health benefit of konjac, which can be attributed to its glucomannan content. A systematic review on glucomannan effects on plasma lipids, fasting blood glucose, blood pressure, and body weight, found that glucomannan reduced plasma LDL cholesterol, total cholesterols and triglycerides(3).
Furthermore, a systematic review and meta-analysis found that three grams of glucomannan from konjac was required to see a beneficial reduction of 10% in LDL cholesterol (4). Overall, it can be concluded that konjac glucomannan fibre has the potential to improve cholesterol levels.
Weight loss is a potential health benefit of the consumption of konjac . A randomized control trial conducted on 176 individuals on a calorie-restricted diet using a supplement containing either glucomannan alone; glucomannan and gar gum; or glucomannan, gar gum, and alginat found that glucomannan alone induced additional bodyweight reduction in addition to calorie restriction(5). This was not found with the other supplements.
The National Institutes of Health’s Office of Dietary Supplements claims that glucomannan has been shown to decrease hunger (6). However, they concluded that it has little to no effect on weight loss. Contrastingly, the study (3) cited in Heart Health, found that glucomannan had positive impacts on healthy body weights. Therefore, more research is necessary to conclude konjac’s weight loss effects.
Adverse effects have been noted with the consumption of konjac. Due to its highly gelatinous properties it may cause digestive stress (rather than being beneficial). Depending on the individuals, symptoms can include bloating, diarrhea or loose stool, abdominal pain, gas, nausea, and possibly esophageal or bowel obstruction. I recommend gradually introducing it into your diet, as with any new, high fibre ingredient/food.
Overall, konjac has a number of potential health benefits due to the soluble fibre glucomannan content. Remember no single food or ingredient is a silver bullet. A lifestyle filled with healthy habits including a balanced dietary pattern, exercise and restful sleep is the best approach for long-term consistent, mind body health. If you have added konjac to your healthy diet, let me know your thoughts about the flavour, texture and how you use it!
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- Chen H-L, Cheng H-C, Wu W-T, Liu Y-J, Liu S-Y. Supplementation of Konjac Glucomannan into a Low-Fiber Chinese Diet Promoted Bowel Movement and Improved Colonic Ecology in Constipated Adults: A Placebo-Controlled, Diet-Controlled Trial. J Am Coll Nutr [Internet]. 2008 Feb 14 [cited 2019 Sep 16];27(1):102–8.
- Han Y, Zhang L, Liu X-Q, Zhao Z-J, Lv L-X. Effect of glucomannan on functional constipation in children: a systematic review and meta-analysis of randomized controlled trials. Asia Pac J Clin Nutr [Internet]. 2017 May [cited 2019 Sep 16];26(3):471–7.
- 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 [Internet]. 2008 Oct 1 [cited 2019 Sep 16];88(4):1167–75.
- Ho HVT, Jovanovski E, Zurbau A, Blanco Mejia S, Sievenpiper JL, Au-Yeung F, et al. A systematic review and meta-analysis of randomized controlled trials of the effect of konjac glucomannan, a viscous soluble fiber, on LDL cholesterol and the new lipid targets non-HDL cholesterol and apolipoprotein B. Am J Clin Nutr [Internet]. 2017 May 1 [cited 2019 Sep 16];105(5):1239–47.
- Birketvedt GS, Shimshi M, Erling T, Florholmen J. Experiences with three different fiber supplements in weight reduction. Med Sci Monit [Internet]. 2005 Jan [cited 2019 Sep 16];11(1):PI5 Available from: http://www.ncbi.nlm.nih.gov/pubmed/15614200
- Dietary Supplements for Weight Loss — Health Professional Fact Sheet [Internet]. [cited 2019 Sep 16]. Available from: https://ods.od.nih.gov/factsheets/WeightLoss-HealthProfessional/
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