Glucomannan and Its Fiber Benefits

Glucomannan is a viscous water-soluble, fermentable dietary fiber. It is made from the root of the elephant yam, also known as the konjac plant (Amorphophallus konjac or Amorphophallus rivieri).

Glucomannan originated in the warm, tropical parts of Asia. Konjac flour is traditionally used in Asian cooking.

Fiber is the indigestible part of carbohydrates that has been studied for its role in heart and gut health, blood sugar control, and weight management.

This article discusses the potential uses of glucomannan. It also covers dosages, side effects, and precautions when taking the supplement.

Uses of Glucomannan

Glucomannan has been studied for its potential role in weight management, bowel regularity, and blood sugar and cholesterol control.

Mixed Results for Weight Management

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.

May Promote Bowel Regularity and Treat Constipation

Constipation can be uncomfortable and affect your quality of life. Oftentimes, nutrition interventions like adding fibrous foods and 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.

May Lower Cholesterol

Some research suggests that glucomannan may be better than other fibers at lowering cholesterol.

In one meta-analysis, which evaluated 370 individuals, researchers determined that taking about 3 g per day of glucomannan reduced low-density lipoprotein (LDL) cholesterol (known as the 'bad" cholesterol) and non-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.

May Help to Reduce Blood Sugar

Glucomannan is thought to lower postprandial (after-meal) blood glucose due 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 reduced fasting blood sugar and 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 with diabetes medications or 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:

• Lowering triglycerides (a type of fat in the blood)
• Lowering blood pressure

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:

• Burping
• Loose stools
• Gas
• Diarrhea
• Constipation
• Abdominal discomfort

The European Food Safety Authority (EFSA) concluded there was no safety concern at less than 3 g per day of glucomannan (konjac) intake for the general population. Abdominal discomfort, including diarrhea or constipation, may occur after this daily dose in adults.

Precautions

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 identify symptoms 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.

Interactions

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.

How to Store

Store glucomannan in a cool, dry, dark place and keep the lid tightly closed. Discard by the expiration date or according to label instructions.

Similar Supplements

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:

• Alramucil
• Fiberall
• Genfiber
• Hydrocil
• Daily Fiber Therapy
• Natural Fiber Therapy
• Natural Vegetable
• Perdiem Fiber
• Reguloid
• Serutan
• Syllact
• Uni-Laxative
• V-Lax

Guar gum and pectin are other types of soluble fibers.

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. When choosing a supplement, look for third-party 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.