Table of ContentsView AllTable of ContentsMixed Results for Weight ManagementMay Promote Bowel Regularity and Treat ConstipationMay Lower CholesterolMay Help to Reduce Blood SugarSide EffectsPrecautionsDosageOveruseInteractionsHow to StoreSimilar SupplementsFrequently Asked QuestionsSources & What to Look For
Table of ContentsView All
View All
Table of Contents
Mixed Results for Weight Management
May Promote Bowel Regularity and Treat Constipation
May Lower Cholesterol
May Help to Reduce Blood Sugar
Side Effects
Precautions
Dosage
Overuse
Interactions
How to Store
Similar Supplements
Frequently Asked Questions
Sources & What to Look For
Glucomannan is adietary fibermade from the root of the elephant yam. It is sometimes used in food as a thickening agent, but many people take it in powder, gummy, or capsule form as a supplement.
Glucomannan has been studied for its potential benefits in weight management, bowel function, and management of blood sugar and cholesterol levels. However, studies investigating its effectiveness have yielded inconsistent results.
In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says. Whenchoosing a supplement, look for independently tested products and consult a healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.
Getty Images / Pricha Tihokam
Glucomannan is one of the most viscous fibers. It can absorb up to 50 times its weight in water.It creates a thick gel when absorbed.
Viscous fibers like glucomannan slow the digestion and absorption of nutrients, which creates a feeling of fullness (satiety). An increase in satiety can reduce food intake.
Studies have evaluated glucomannan’s effect on weight loss. However, results have been mixed.
In one trial, researchers evaluated the use of glucomannan in 53 participants with a body mass index (BMI) of 25 to 35. Participants received either 1.33 grams (g) of glucomannan capsules or placebo capsules with 8 ounces of water one hour before breakfast, lunch, and dinner for eight weeks. Overall, glucomannan was well tolerated, but it did not produce significant weight loss results.
A review of six clinical trials suggested that short-term use of glucomannan may help reduce body weight, although BMI was not affected. The studies included people who were overweight or had obesity, but were otherwise healthy.
However, the data is too limited to recommend trying glucomannan as a weight-loss aid.
Weight loss is complicated and is different for everyone. An individualized approach that accounts for a person’s goals, dietary history, culture, medical history, lifestyle, and sustainability is important to a weight management plan.
Constipationcan be uncomfortable and affect your quality of life. Oftentimes, nutrition interventions like addingfibrous foodsand drinking more water is the first line of treatment. Sometimes, fiber supplements are used.
In a randomized control trial, researchers investigated using glucomannan to treat constipation in pregnant people in their third trimester. For one month, participants took 4 g of powdered glucomannan in divided doses twice daily with water.
After one month of supplementation, the participants had increased bowel movements and positive changes in stool consistency.
Some research suggests that glucomannan may be better than other fibers at loweringcholesterol.
In one meta-analysis,which evaluated 370 individuals, researchers determined that taking about 3 g per day of glucomannan reducedlow-density lipoprotein (LDL) cholesterol(known as the ‘bad" cholesterol) andnon-high-density lipoprotein (HDL) cholesterol(a measure of the “bad” types of cholesterol in the body).
Most studies administered glucomannan as powdered capsules, bars, biscuits, or yogurt, with doses ranging from 2.0 to 15.1 g per day. Studies lasted from three to 12 weeks.
Glucomannan is thought to lower postprandial (after-meal)blood glucosedue to its ability to absorb water, reducing food digestion and absorption. Researchers investigated its use in people with type 2 diabetes.
In a meta-analysis of six studies, supplementation with glucomannan significantly reducedfasting blood sugarand two-hour postprandial blood sugar.Doses ranged from 1.2 g to 15 g daily, and the duration of the experiments ranged from three to 16 weeks.
However, it is unclear whether glucomannan was consumed withdiabetes medicationsor in conjunction with diet and exercise. Therefore, it should not be assumed that it can replace standard-of-care methods but rather it can be used in addition to diet, exercise, and pharmacologic therapy.
Based on studies, other potential benefits include:
Larger-scale trials are needed to confirm these findings.
What Are the Side Effects of Glucomannan?
Most studies have evaluated glucomannan use in the short term, and not much is known about long-term safety. Short-term use appears to be well-tolerated.
Minor potential side effects include:
If you take glucose-lowering medications(oral medicines or insulin),you may need to monitor your blood sugar more often, as glucomannan can have a blood sugar-lowering effect.
Because of this, you should know how to identifysymptoms of hypoglycemia and know how to treat it. If you have low blood sugar often, contact your medical team. You may need a change in your treatment regimen.
Before starting new supplements, let your healthcare provider know, especially if you also take prescription or over-the-counter (OTC) medications. Drug-supplement interactions can be avoided with proper timing.
Lastly, when taking glucomannan, it is very important to drink ample amounts of water.
Dosage: How Much Glucomannan Should I Take?
Although there is no set dosing regimen, taking around 3 g daily may be best to reduce the risk of gastrointestinal (GI) symptoms.
If you are new to taking the supplement, you may want to break up the doses and take smaller amounts to start as your body adjusts.
What Happens If I Take Too Much Glucomannan?
Too much glucomannan can cause gas, bloating, stomach cramps, and diarrhea. Excess amounts, especially without water, may increase the risk of choking or esophageal obstruction.
Glucomannan may reduce how much medicine your body absorbs. Therefore, discussing the timing of taking medications and supplements with your healthcare provider before use is important.
It is essential to carefully read the ingredient list and nutrition facts panel of glucomannan to know which and how much of each ingredient is included. Review the supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.
Other water-soluble fibers may produce similar results. For example, psyllium (commonly known as the brand name Metamucil), is another type of soluble fiber that has been shown to help increase satiety and relieve constipation.
Other types of psyllium supplements include brand names like:
Guar gum and pectin are other types of soluble fibers.
Frequently Asked QuestionsTake glucomannan with at least 8 ounces of water. Many studies suggest taking it before meals to help increase feelings of fullness. Start slowly and increase gradually to prevent gastrointestinal side effects.If you are taking any medications, discuss the timing of supplementation with your healthcare provider. Glucomannan can affect the way your medicine is absorbed.Getting your fiber needs through food first is the best approach. Eating fiber-rich foods like fruit, vegetables, whole grains, nuts, and seeds provides you with fiber and contributes to your daily needs of other essential vitamins, minerals, and antioxidants.
Take glucomannan with at least 8 ounces of water. Many studies suggest taking it before meals to help increase feelings of fullness. Start slowly and increase gradually to prevent gastrointestinal side effects.If you are taking any medications, discuss the timing of supplementation with your healthcare provider. Glucomannan can affect the way your medicine is absorbed.
Take glucomannan with at least 8 ounces of water. Many studies suggest taking it before meals to help increase feelings of fullness. Start slowly and increase gradually to prevent gastrointestinal side effects.
If you are taking any medications, discuss the timing of supplementation with your healthcare provider. Glucomannan can affect the way your medicine is absorbed.
Getting your fiber needs through food first is the best approach. Eating fiber-rich foods like fruit, vegetables, whole grains, nuts, and seeds provides you with fiber and contributes to your daily needs of other essential vitamins, minerals, and antioxidants.
Sources and What to Look For
Glucomannan can be added to foods or used to make foods. It is also found in powder, capsule, and tablet form.
Food Sources of Glucomannan
Shirataki noodles are made from glucomannan. Other food sources that contain glucomannan include konjac jelly and tofu.
Konjac flour, which is pure soluble fiber, contains no starch or sugar and is available as a food thickener. It is often used to thicken gravy, sauces, soups, and stews and can be used in baked goods. To use, you must mix the thickener with a liquid and then add it to your food.
Glucomannan Supplements
Glucomannan supplements come in gummies, pill, powder, and tablet forms. The powders are virtually tasteless; therefore, they can be added to smoothies, yogurt, and other foods.
In the United States, the Food and Drug Administration (FDA) does not regulate supplements the way it regulates prescription drugs. That means some supplement products may not contain what the label says. Whenchoosing a supplement, look for independent tested products and consult a healthcare provider, registered dietitian nutritionist (RD or RDN), or pharmacist.
Summary
Glucomannan is a type of viscous, soluble fiber that has been studied for its use in weight management, regulating bowels, and lowering cholesterol and blood sugar. It appears to be safe with short-term use.
However, despite their potential health benefits, supplements should never replace a nutrition eating plan or other healthy lifestyle changes. It’s generally recommended to meet your fiber needs with the right diet. Still, under the supervision of a healthcare provider or registered dietitian nutritionist, glucomannan may be used as an add-on to lifestyle interventions.
11 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Watanabe M, Risi R, Masi D, et al.Current evidence to propose different food supplements for weight loss: a comprehensive review.Nutrients. 2020;12(9):2873. doi:10.3390/nu12092873National Institutes of Health’s Office of Dietary Supplements.Dietary supplements for weight loss: glucomannan.Keithley JK, Swanson B, Mikolaitis SL, et al.Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults.J Obes.2013;2013:610908. doi:10.1155/2013/610908Zalewski BM, Chmielewska A, Szajewska H.The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials.Nutrition. 2015;31(3):437-42.e2. doi:10.1016/j.nut.2014.09.004Janani F, Changaee F.The effect of glucomannan on pregnancy constipation.J Family Med Prim Care.2018;7(5):903-906. doi: 10.4103/jfmpc.jfmpc_168_18Ho HVT, Jovanovski E, Zurbau A, 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.2017;105(5):1239-1247. doi:10.3945/ajcn.116.142158Zhang Z, Zhang Y, Tao X, Wang Y, Rao B, Shi H.Effects of glucomannan supplementation on type II diabetes mellitus in humans: a meta-analysis.Nutrients.2023;15(3):601. doi:10.3390/nu15030601Devaraj RD, Reddy CK, Xu B.Health-promoting effects of konjac glucomannan and its practical applications: a critical review.International Journal of Biological Macromolecules.2019;126:273-281. doi:10.1016/j.ijbiomac.2018.12.203EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS); Mortensen A, Aguilar F, Crebelli R, et al.Re-evaluation of konjac gum (E 425 i) and konjac glucomannan (E 425 ii) as food additives.EFSA J. 2017;15(6):e04864. doi:10.2903/j.efsa.2017.4864Xiao Z, Chen H, Zhang Y, et al.The effect of psyllium consumption on weight, body mass index, lipid profile, and glucose metabolism in diabetic patients: a systematic review and dose-response meta-analysis of randomized controlled trials.Phytother Res.2020;34(6):1237-1247. doi:10.1002/ptr.6609Nagasawa T, Kimura T, Yoshida A, et al.Konjac glucomannan attenuated triglyceride metabolism during rice gruel tolerance test.Nutrients.2021;13(7):2191.
11 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Watanabe M, Risi R, Masi D, et al.Current evidence to propose different food supplements for weight loss: a comprehensive review.Nutrients. 2020;12(9):2873. doi:10.3390/nu12092873National Institutes of Health’s Office of Dietary Supplements.Dietary supplements for weight loss: glucomannan.Keithley JK, Swanson B, Mikolaitis SL, et al.Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults.J Obes.2013;2013:610908. doi:10.1155/2013/610908Zalewski BM, Chmielewska A, Szajewska H.The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials.Nutrition. 2015;31(3):437-42.e2. doi:10.1016/j.nut.2014.09.004Janani F, Changaee F.The effect of glucomannan on pregnancy constipation.J Family Med Prim Care.2018;7(5):903-906. doi: 10.4103/jfmpc.jfmpc_168_18Ho HVT, Jovanovski E, Zurbau A, 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.2017;105(5):1239-1247. doi:10.3945/ajcn.116.142158Zhang Z, Zhang Y, Tao X, Wang Y, Rao B, Shi H.Effects of glucomannan supplementation on type II diabetes mellitus in humans: a meta-analysis.Nutrients.2023;15(3):601. doi:10.3390/nu15030601Devaraj RD, Reddy CK, Xu B.Health-promoting effects of konjac glucomannan and its practical applications: a critical review.International Journal of Biological Macromolecules.2019;126:273-281. doi:10.1016/j.ijbiomac.2018.12.203EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS); Mortensen A, Aguilar F, Crebelli R, et al.Re-evaluation of konjac gum (E 425 i) and konjac glucomannan (E 425 ii) as food additives.EFSA J. 2017;15(6):e04864. doi:10.2903/j.efsa.2017.4864Xiao Z, Chen H, Zhang Y, et al.The effect of psyllium consumption on weight, body mass index, lipid profile, and glucose metabolism in diabetic patients: a systematic review and dose-response meta-analysis of randomized controlled trials.Phytother Res.2020;34(6):1237-1247. doi:10.1002/ptr.6609Nagasawa T, Kimura T, Yoshida A, et al.Konjac glucomannan attenuated triglyceride metabolism during rice gruel tolerance test.Nutrients.2021;13(7):2191.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Watanabe M, Risi R, Masi D, et al.Current evidence to propose different food supplements for weight loss: a comprehensive review.Nutrients. 2020;12(9):2873. doi:10.3390/nu12092873National Institutes of Health’s Office of Dietary Supplements.Dietary supplements for weight loss: glucomannan.Keithley JK, Swanson B, Mikolaitis SL, et al.Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults.J Obes.2013;2013:610908. doi:10.1155/2013/610908Zalewski BM, Chmielewska A, Szajewska H.The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials.Nutrition. 2015;31(3):437-42.e2. doi:10.1016/j.nut.2014.09.004Janani F, Changaee F.The effect of glucomannan on pregnancy constipation.J Family Med Prim Care.2018;7(5):903-906. doi: 10.4103/jfmpc.jfmpc_168_18Ho HVT, Jovanovski E, Zurbau A, 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.2017;105(5):1239-1247. doi:10.3945/ajcn.116.142158Zhang Z, Zhang Y, Tao X, Wang Y, Rao B, Shi H.Effects of glucomannan supplementation on type II diabetes mellitus in humans: a meta-analysis.Nutrients.2023;15(3):601. doi:10.3390/nu15030601Devaraj RD, Reddy CK, Xu B.Health-promoting effects of konjac glucomannan and its practical applications: a critical review.International Journal of Biological Macromolecules.2019;126:273-281. doi:10.1016/j.ijbiomac.2018.12.203EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS); Mortensen A, Aguilar F, Crebelli R, et al.Re-evaluation of konjac gum (E 425 i) and konjac glucomannan (E 425 ii) as food additives.EFSA J. 2017;15(6):e04864. doi:10.2903/j.efsa.2017.4864Xiao Z, Chen H, Zhang Y, et al.The effect of psyllium consumption on weight, body mass index, lipid profile, and glucose metabolism in diabetic patients: a systematic review and dose-response meta-analysis of randomized controlled trials.Phytother Res.2020;34(6):1237-1247. doi:10.1002/ptr.6609Nagasawa T, Kimura T, Yoshida A, et al.Konjac glucomannan attenuated triglyceride metabolism during rice gruel tolerance test.Nutrients.2021;13(7):2191.
Watanabe M, Risi R, Masi D, et al.Current evidence to propose different food supplements for weight loss: a comprehensive review.Nutrients. 2020;12(9):2873. doi:10.3390/nu12092873
National Institutes of Health’s Office of Dietary Supplements.Dietary supplements for weight loss: glucomannan.
Keithley JK, Swanson B, Mikolaitis SL, et al.Safety and efficacy of glucomannan for weight loss in overweight and moderately obese adults.J Obes.2013;2013:610908. doi:10.1155/2013/610908
Zalewski BM, Chmielewska A, Szajewska H.The effect of glucomannan on body weight in overweight or obese children and adults: a systematic review of randomized controlled trials.Nutrition. 2015;31(3):437-42.e2. doi:10.1016/j.nut.2014.09.004
Janani F, Changaee F.The effect of glucomannan on pregnancy constipation.J Family Med Prim Care.2018;7(5):903-906. doi: 10.4103/jfmpc.jfmpc_168_18
Ho HVT, Jovanovski E, Zurbau A, 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.2017;105(5):1239-1247. doi:10.3945/ajcn.116.142158
Zhang Z, Zhang Y, Tao X, Wang Y, Rao B, Shi H.Effects of glucomannan supplementation on type II diabetes mellitus in humans: a meta-analysis.Nutrients.2023;15(3):601. doi:10.3390/nu15030601
Devaraj RD, Reddy CK, Xu B.Health-promoting effects of konjac glucomannan and its practical applications: a critical review.International Journal of Biological Macromolecules.2019;126:273-281. doi:10.1016/j.ijbiomac.2018.12.203
EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS); Mortensen A, Aguilar F, Crebelli R, et al.Re-evaluation of konjac gum (E 425 i) and konjac glucomannan (E 425 ii) as food additives.EFSA J. 2017;15(6):e04864. doi:10.2903/j.efsa.2017.4864
Xiao Z, Chen H, Zhang Y, et al.The effect of psyllium consumption on weight, body mass index, lipid profile, and glucose metabolism in diabetic patients: a systematic review and dose-response meta-analysis of randomized controlled trials.Phytother Res.2020;34(6):1237-1247. doi:10.1002/ptr.6609
Nagasawa T, Kimura T, Yoshida A, et al.Konjac glucomannan attenuated triglyceride metabolism during rice gruel tolerance test.Nutrients.2021;13(7):2191.
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