Glucomannan for Diabetes Defense: Can It Help?

Konjac plant
Glucomannan is sourced from the konjac root. IMAGEMORE Co, Ltd./Getty Images

Glucomannan is a fiber-rich substance extracted from the konjac root. Rich in soluble fiber (the type of fiber that attracts water and becomes a gel during digestion), glucommannan is sometimes used to fight diabetes.

Proponents claim that glucomannan can help keep blood sugar levels in check and lower cholesterol levels. It can be found in dietary supplement form or naturally in foods such as shirataki noodles.

The Benefits of Glucomannan for Diabetes

To date, relatively few studies have tested glucomannan's effectiveness against diabetes. However, several small studies suggest that glucomannan may offer certain benefits to people with diabetes.

For instance, a 2003 study published in the Journal of the American College of Nutrition found that four weeks of treatment with glucomannan supplements helped guard against elevated glucose levels and improved cholesterol levels in people with diabetes. The study involved 22 people with diabetes and high cholesterol who were not taking cholesterol medication. Results showed that glucomannan was superior to a placebo in reducing LDL cholesterol and fasting glucose levels (a measure of blood sugar after not eating or drinking for at least eight hours).

There's also some evidence that including glucomannan in your diet may help improve diabetes control. In a small 2000 study from Diabetes Care, for example, people ate glucomannan-enriched biscuits or biscuits enriched with wheat bran fiber every day for three weeks.

Researchers found that consumption of the biscuits lead to greater improvements in blood sugar control and a greater decrease in cholesterol.

Additionally, taking glucomannan in combination with plant sterols (naturally occurring compounds with cholesterol-lowering effects) may help diabetes patients keep their cholesterol in check, according to a 2006 study published in the European Journal of Clinical Nutrition.

For the study, 16 people with diabetes and 18 non-diabetic individuals were assigned to one of four treatments for 21 days: supplements containing plant sterols, supplements containing glucomannan, supplements containing a combination of glucomannan and plant sterols, or a placebo. Results indicated that the combination of glucomannan and plant sterols was most effective at lowering LDL cholesterol.

Possible Side Effects

Although consuming glucomannan powder or flour in limited amounts in foods (such as shirataki noodles) is generally considered acceptable, little is known about the health effects of long-term or regular use of glucomannan supplements. There's some concern that taking glucomannan supplements in combination with diabetes medication may reduce your blood sugar to dangerously low levels.

Since solid tablets of glucomannan may cause blockages in the throat or intestines, some health professionals recommend opting for the powder form mixed with water.

Fiber supplements can interfere with the absorption of minerals, so it's a good idea to take vitamin and mineral supplements several hours apart from glucomannan.

Self-treating with glucomannan and avoiding or delaying standard diabetes prevention or treatment may have serious health consequences.

Keep in mind that supplements haven't been tested for safety and dietary supplements are largely unregulated. In some cases, the product may deliver doses that differ from the specified amount for each herb. In other cases, the product may be contaminated with other substances such as metals. Also, the safety of supplements in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications has not been established. You can get further tips on using supplements here.

Where to Find It

Widely available for purchase online, glucomannan capsules, pills, powder, flour and other supplements can be found in many natural-foods stores and in stores specializing in dietary supplements.

Glucomannan is also known as Amorphophallus konjac, konjac mannan, and konjac fiber.

Final Thoughts

If you're considering the use of glucomannan supplements for the treatment or prevention of diabetes (or any other condition), it's important to consult your physician prior to starting your supplement regimen. 

There's some evidence that ginseng, cinnamon, and fenugreek may protect against diabetes. In addition, drinking tea on a regular basis and maintaining optimal vitamin D levels may also help.


Chen HL, Sheu WH, Tai TS, Liaw YP, Chen YC. Konjac supplement alleviated hypercholesterolemia and hyperglycemia in type 2 diabetic subjects--a randomized double-blind trial. J Am Coll Nutr. 2003 Feb;22(1):36-42.

Vuksan V, Jenkins DJ, Spadafora P, et al. Konjac-mannan (glucomannan) improves glycemia and other associated risk factors for coronary heart disease in type 2 diabetes. A randomized controlled metabolic trial. Diabetes Care. 1999 Jun;22(6):913-9.

Vuksan V, Sievenpiper JL, Owen R, et al. Beneficial effects of viscous dietary fiber from Konjac-mannan in subjects with the insulin resistance syndrome: results of a controlled metabolic trial. Diabetes Care. 2000 Jan;23(1):9-14.

Yoshida M, Vanstone CA, Parsons WD, Zawistowski J, Jones PJ. Effect of plant sterols and glucomannan on lipids in individuals with and without type II diabetes. Eur J Clin Nutr. 2006 Apr;60(4):529-37.

Disclaimer: The information contained on this site is intended for educational purposes only and is not a substitute for advice, diagnosis or treatment by a licensed physician. It is not meant to cover all possible precautions, drug interactions, circumstances or adverse effects. You should seek prompt medical care for any health issues and consult your doctor before using alternative medicine or making a change to your regimen.

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