Side Effects of Glucomannan

Glucomannan, a type of water-soluble fiber that comes mainly from the dried root of the konjac plant, is used by the food industry as a thickener. However, glucomannan supplements are also used for other purposes. For example, they may help you lose weight and lower your blood sugar and cholesterol levels, according to a study published in "The American Journal of Clinical Nutrition" in October 2008. Glucomannan may cause side effects or interfere with certain medications, so check with your doctor before using this supplement.

While glucomannan may help with weight loss, it does have some potential side effects. (Image: Creatas Images/Creatas/Getty Images)

Gastrointestinal Effects

Gastrointestinal effects (Image: Jupiterimages/Polka Dot/Getty Images)

Glucomannan, like other types of soluble fiber, can cause gastrointestinal side effects when you suddenly increase the amount you consume. These can include bloating, stomach pains, loose stools, flatulence and diarrhea. While diarrhea can be a side effect, this doesn't mean glucomannan is effective for treating constipation. A study published in "Clinical Nutrition" in August 2011 found that glucomannan wasn't beneficial for treating functional constipation in children.

Blood Sugar Effects

Blood test (Image: Purestock/Purestock/Getty Images)

Soluble fiber, like glucomannan, soaks up water and forms a gel in your digestive tract, which slows down the emptying of the stomach. This slows down the absorption of glucose into the blood and can lower your blood sugar levels. People with diabetes should be careful when using glucommanan to avoid decreasing their blood sugar levels too much.

Choking Risk

Drink plenty of water with the supplement (Image: Creatas Images/Creatas/Getty Images)

Don't use glucomannan if you have any blockages in your digestive tract or if you have structural abnormalities in your gut or esophagus. Take this supplement as directed with plenty of water, as there have been incidences of choking when the tablets become lodged in the esophagus and swell.

Potential Medication Interactions

Potential medication interactions (Image: Jupiterimages/Polka Dot/Getty Images)

Since glucomannan slows stomach emptying, it may also interfere with certain medications, so only take this supplement either an hour after your other medications or four hours before you take your medications, according to Glucomannan may also interact with any medications that can lower blood sugar, such as insulin or diabetes medications.

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