A late-night scroll through social media can feed you a whole bunch of dietary advice. You’ll see some (typically overstated) reports that a trendy food or supplement is a one-stop-shop for curing all of life’s pain points, from improving gut health to weight loss (which may not even be necessary). Konjac is a popular ingredient in low-carb diets like keto.
“Konjac is a root vegetable native to Southeast Asia, often used as a low-carbohydrate alternative to aid in weight management and digestive health due to its unique soluble fiber, known as glucomannan,” explains Michelle Routhenstein, MS, RD, CDCES, CDN, a preventive cardiology dietitian and certified diabetes educator at EntirelyNourished.com.
Does konjac live up to the hype? Registered dietitians gave the 4-1-1 on konjac, including its reported benefits, risks, taste and where you’ll find it.
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What Is Konjac?
TL;DR: Konjac (pronounced kaan-jak) is a root perennial plant with origins in China and Southeast Asia, explains Jessie Anderson, MS, RD, CSSD, LD, ACSM EP-C, a registered dietitian with Top Nutrition Coaching. She says that you may see it referred to as devil’s tongue, elephant yam, snake palm, voodoo lily and konnyaku potato.
Anderson explains that Konjac plant roots are starchy and edible.
“[They are] high in soluble fiber while low in calories, carbohydrate and fat,” she adds.
As a result, Anderson reports that konjac, which has a 2,000-year history in China and Southeast Asia, has gained favor in the U.S. for its potential use in preventing and treating cardiometabolic, gastrointestinal and immunological conditions. You’ll often find it manufactured into flour, jelly, noodles and dietary supplements.
“Konjac contains the water-soluble dietary fiber called glucomannan. According to a 2024 Nutrientsstudy, glucomannan can delay stomach emptying, prolong satiety and help with weight loss.
That may sound familiar—GLP-1s like Ozempic have a similar effect. However, unlike Ozempic, supplements are not regulated as drugs by the Food and Drug Administration (FDA). The FDA doesn’t approve dietary supplements for safety and effectiveness before they hit shelves. In 2021, the FDA sent a warning letter to Genesis Nutrition Ultra Slim about one of its weight loss supplements with konjac regarding pharmaceutical ingredients it contained that were known for heart attack and stroke risks.
Routhenstein recommends consulting a doctor before taking any supplements, including ones containing konjac.
“It may interact with certain medications that help lower blood sugar levels during meals, as it slows down the absorption of food,” Routhenstein says. “It is best to consult your healthcare team to determine if it’s a suitable option for you.”
Related: The Superfood That Kept Me Full When I Stopped Taking Ozempic
What Does Konjac Taste Like?
Not much. “Konjac has a neutral taste that allows it to absorb the flavors of the ingredients added to it, while its texture is slightly rubbery and gelatinous,” Routhenstein says.
In other words, konjac is a chameleon, adapting its taste to the main dish’s, according to Anderson. If you do taste a little something, it may remind you of a time you hung zero during a surfing lesson and got a cool drink of water you didn’t want.
“It carries a slight salty ocean-like taste,” she explains.
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Where To Find Konjac and How To Cook With It
Routhenstein reports that you can often find konjac in health food and Asian grocery stores. Konjac comes in various forms, which dictate how you’ll use it in recipes.
Anderson says the most popular ways to use konjac are:
- Konjac flour. Take a seat, sourdough.Anderson says konjac flour is frequently used to prepare gluten-free breads, shirataki noodles and shirataki rice.
- Konjac jelly.This one is for the sweet tooths. “Konjac jelly is often used in the preparation of low-calorie, fiber-rich desserts and snacks,” Anderson explains. “Due to its stable gel-like texture, Konjac is often used as a vegan-friendly alternative to gelatin in desserts, puddings and candies.”
- Dietary supplements. Anderson notes that konjac glucomannan is a good source of soluble fiber, so it is often manufactured into dietary supplements that promise to help with diarrhea, cardiometabolic and gastrointestinal health.
Related: This Beverage Could Lower Your Type 2 Diabetes Risk By 19%
Is Konjac Good For You? 3 Potential Benefits
1. Cholesterol
Anderson points to recent research showing that konjac may have cholesterol-improving effects. It contains glucomannan. In 2020, the FDA noted that glucomannan may help lower blood cholesterol levels, which was a big reason why the federal agency moved to expand the definition of dietary fiber to include glucomannan.
A 2021 Biomoleculesreview also indicated that konjac could improve blood cholesterol.
2. Blood sugar
The 2021 Biomolecules review also suggested that konjac could help lower blood sugar levels. A 2022 Food Science and Technology review even suggested that konjac might help treat and prevent diabetes.
“Konjac aids in the slowing of digestion while enhancing activity of enzymes involved in glucose metabolism,” Anderson says.
She explains that these properties improve insulin sensitivity and prevent significant blood sugar spikes after you eat.
3. Gut health
Gut health has become buzzy of late, but the 2021 Biomolecules review had some data that indicated that konjac may, in fact, boost digestion.
“The unique fiber in konjac can support gut health because it acts as a prebiotic, feeding beneficial gut bacteria and helping with bowel movements,” Routhenstein explains.
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Risks of Konjac
Supplements can be recalled or raise alarm bells. We mentioned above how the FDA raised alarm bells about the ingredients in Genesis Ultra Slim. Plus, supplements can interfere with or interact poorly with medications, so it is important to speak with a doctor and dietitian and check for recalls on products you are interested in.
Besides those basics—which are true for any supplement—Anderson says you’ll also want to be mindful of the fiber in konjac. Fiber is important, but she points out that many people aren’t consuming enough (38 grams per day for men and 25 grams per day for women).
“It is encouraged to increase gradually dietary fiber intake by three to four every three to four days,” Anderson says.
Before increasing your intake, ensure you’re not experiencing unwanted side effects like bloating, cramping and hiccups. Drinking plenty of fluids will help with digestion. Also, konjac’s gel-like texture can be a choking hazard for some.
“It is recommended for those who have difficulty swallowing and for young children to avoid Konjac,” Anderson explains.
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Sources:
- Michelle Routhenstein, MS, RD, CDCES, CDN, a preventive cardiology dietitian and certified diabetes educator at EntirelyNourished.com
- Jessie Anderson, MS, RD, CSSD, LD, ACSM EP-C, a registered dietitian with Top Nutrition Coaching
- The Impact of Glucomannan, Inulin, and Psyllium Supplementation (SolowaysTM) on Weight Loss in Adults with FTO, LEP, LEPR, and MC4R Polymorphisms: A Randomized, Double-Blind, Placebo-Controlled Trial. Nutrients.
- FDA 101: Dietary Supplements. FDA.
- Genesis Nutrition Ultra Slim dba Genesis Ultra Slim. FDA.
- FDA Grants Citizen Petition on Glucomannan as a Dietary Fiber. FDA.
- Plant Prebiotics and Their Role in the Amelioration of Diseases. Biomolecules.
- Open-access Research progress of konjac dietary fibre in the prevention and treatment of diabetes. Food Science and Technology.
- Closing America’s Fiber Intake Gap. American Journal of Lifestyle Medicine.