Background

Glucomannan is a dietary fiber usually made from the root of the konjac plant. It's historically been used as food and medicine in Asian cultures.

Glucomannan might work in the stomach and intestines by absorbing water to form a bulky fiber which treats constipation. It might also slow the absorption of sugar and cholesterol in the gut, helping to control sugar levels in people with diabetes and reduce cholesterol levels.

People commonly use glucomannan for constipation, diabetes, and high cholesterol. It's also used for high blood pressure, obesity, and many other conditions, but there is no good scientific evidence to support most of these uses.

Safety Safety definitions

When taken by mouth: Glucomannan powder and flour are commonly consumed in foods. Glucomannan powder and capsules are possibly safe when taken with plenty of water for up to 4 months. But taking glucomannan products without water, especially as tablets, is possibly unsafe. These products might cause choking and other serious side effects when taken without water.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if glucomannan is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Children: Glucomannan powder and capsules are possibly safe for most children when taken with plenty of water for up to 4 months. But taking glucomannan products without water, especially as tablets, is likely unsafe. These products might cause choking and other serious side effects when taken without water.

Effectiveness

Dosing & administration

In foods, glucomannan powder or flour is commonly used as a thickening agent and as a source of dietary fiber.

As medicine, glucomannan has most often been used by adults in doses of 3-4 grams by mouth daily for up to 3 months. In children, glucomannan has most often been used in doses of 2-5 grams by mouth daily for up to 4 months. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

Medications taken by mouth (Oral drugs)

Interaction Rating=Moderate Be cautious with this combination.

Taking glucomannan along with medications taken by mouth can decrease how much medicine the body absorbs. To prevent this interaction, take glucomannan at least one hour after medications you take by mouth.

Interactions with herbs & supplements

Vitamin A: Glucomannan may reduce the body's ability to absorb fat-soluble vitamins such as vitamin A.
Vitamin D: Glucomannan may reduce the body's ability to absorb fat-soluble vitamins such as vitamin D.
Vitamin E: Glucomannan may reduce the body's ability to absorb fat-soluble vitamins such as vitamin E.
Vitamin K: Glucomannan may reduce the body's ability to absorb fat-soluble vitamins such as vitamin K.

Interactions with foods

Glucomannan might reduce the body's ability to absorb fat-soluble vitamins, such as vitamins A, D, E, and K. But it doesn't seem to affect water-soluble vitamins, such as vitamin C and B vitamins.