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Glucomannan Weight Loss Side Effect Warnings You Need to Know

Tim Boyer's picture

Glucomannan has recently been televised as a safe and effective weight loss supplement that acts as a natural appetite suppressant. However, what few people are aware of is a side effect warning that taking the wrong type of glucomannan or taking glucomannan the wrong way can cause serious esophageal or intestinal damage that requires emergency surgery.

Glucomannan is a water-soluble dietary fiber derived from the root of a plant named “Amorphophallus konjac,” which grows in warm subtropical regions of Asia. It is also known by other names such as konjak, konjaku, and konnyaku potato. Due to its swelling properties, glucomannan is often used as a food additive as a thickener.

However, because of its ability to absorb water and swell many times the normal size of its dried state, glucomannan is more popularly known as a potential weight loss supplement that acts as an appetite suppressant. It suppresses appetite by essentially expanding and filling the space within the stomach to give a feeling of fullness.

Currently, only a few small studies suggest that taking glucomannan may result in significant weight loss for some dieters.

In one study 20 moderately overweight women were divided into a treatment group and a placebo group. The treatment group received 1 gram of glucomannan 3 times a day for 8 weeks while the control group took a placebo throughout the testing period. What the results showed was that the treatment group lost an average of 5.5 pounds whereas the placebo group gained an average of 1.5 pounds.

However, neither group was closely monitored regarding how much each member of their respective group consumed during the testing. Furthermore, the numbers were too small to be statistically significant. Therefore the study only suggests that taking glucomannan may lead to weight loss.

In spite of the lack of more thorough studies, what is accepted is the fact that taking glucomannan does lead to feelings of fullness and therefore may suppress appetite in some people.

Taking glucomannan typically leads to slightly uncomfortable side effects such as gas, bloating, nausea, abdominal pain and diarrhea. More serious complaints of taking glucomannan can be traced to individuals sensitive to glucomannan that experienced allergic reactions such as a rash, hives, itching, swelling of the mouth or throat, wheezing, or difficulty breathing.

However, what many do not know is that there have been reports of side effects that became medical emergencies requiring surgery for some users of glucomannan that involve blockages of the esophagus, blockages of the intestines and/or intestinal damage to the point of potential rupture.

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A search of literature related to the safety of taking glucomannan reveals reports that taking a tablet form rather than the capsule form of glucomannan can result in the tablet sticking to the tissues of the esophagus and hindering swallowing. The problem becomes compounded when water is taken to wash the stuck tablet and instead causes the tablet to swell further and increase blockage.

In a WebMD “User Reviews and Ratings” of glucomannan, one reviewer stated that her daughter took a glucomannan pill for two months and developed internal bleeding that had to be treated at an emergency room. Presumably from the review, the glucomannan had expanded to such a degree in her daughter’s intestines that it was damaging the tissues and causing the bleeding.

Apparently, because of glucomannan’s ability to swell considerably, the form of glucomannan taken may make a difference. One suggestion is that tablet forms should be totally avoided because of their potential to swell before reaching the stomach and that users should use only the capsule form to prevent the chance of early esophageal swelling.

Another more sensible suggestion has been that glucomannan should be dissolved in water first and then consumed. In fact, on The Dr. Oz Show, Dr. Oz does tell viewers to be sure to dissolve the glucomannan in a shake or other drink before consuming.

Aside from the potential serious consequences of esophageal and intestinal blockage from taking glucomannan, there is also the potential that glucomannan may inhibit the absorption of nutrients and some medications. Experts advise people who wish to try to lose weight using glucomannan as a weight loss supplement should see their physician first to ensure that it will not affect their current medication usage.

Follow this link for information about safe and natural appetite suppressants.


“Glucomannan and risk of oesophageal obstruction” British Medical Journal 1986; 292(6520):591-92; David A. Henry et al.

NYU Langone Medical Center

WebMD User Reviews and Ratings

Updated 6/18/2014



I take ur drugs. Am on a durg. Can ur durg effect me.
Pls i want ur number to call. Thank u.
Bettina - Do you have a doctor? Please see a health care specialist if you have concerns about taking this drug.
I taking glucomannan and i have rash what should i do please
I have GERD and had my symptoms under control. Since using this product (in powder form) my symptoms have returned and I now have stomach soreness also. Is this coincidence or likely to be related ?
My testes swell after ingesting gluco. What up with that.
I've tried the kojnac noodles three times now and felt super nauseous the rest of the night. Last night I was wheezing. I won't be eating these again.
i love glucomannan powder, i mix it with citrucell and chia seeds and drink it for breakfast ... and before bed.... stay away from carbs or you will get the side effects described above. It is a diabetics dream come true. weight loss aid also.