Many sugar-free chewing gums contain a sweetener called sorbitol. Sorbitol is a laxative which is poorly absorbed by the small intestine. An article in this week's British Medical Journal (BMJ) warns of the dangers of excess sorbitol intake.

The warning comes after doctors came across two patients who had chronic diarrhea, abdominal pain and dangerously excessive weight loss. After lengthy investigations which could not identify why the patients were losing so much weight and had chronic diarrhea and pains, a detailed analysis of eating habits put the problem down to eating too much chewing gum with sorbitol.

One of the patients, a 21-year-old woman, had been eating the equivalent of 18-20g of sorbitol each day. The average stick of gum has about 1.25g sorbitol - so, she was chewing through 15-18 sticks of gum each day. The other patient, a 46-year-old man, was chewing about 20 sticks of sorbitol-containing gum plus approximately 200g of sweets (candy) each day - his total sorbitol daily intake was about 30g, the authors wrote.

As soon as sorbitol intake was stopped, both patients started having normal bowel movements (diarrhea subsided) and normal weight gain was achieved.

The authors say consumers are generally unaware of the possible side-effects of sorbitol, even though details are included in the small print of foods containing it. When consumers have gastronomical problems they are unaware that they may be caused by the laxative effects of sorbitol.

The authors conclude that sorbitol consumption may not only cause chronic diarrhea and functional bowel complaints, but also significant unplanned weight loss of about 20% of body weight. Any investigation of unexplained weight loss should include a detailed dietary history with regard to sorbitol-containing foods.

What is Sorbitol?

Also known as glucitol, sorbitol is a sugar alcohol. The body metabolizes it slowly. It is obtained by reduction of glucose changing the ether group to an addition hydroxyl group - hence the name sugar alcohol.

Sorbitol can be found in cough syrups, sugar free mints, chewing gum, diet foods, diet drinks and ice creams. Sorbitol occurs naturally in some stone fruits and berries from trees of the Sorbus genus.

Sorbitol provides dietary energy of 2.6 kilocalories (11 kilojoules) per gram, compared to sugar which provides about 4 kilocalories (17 kilojoules). Sorbitol retains 60% of the sweetness.

As a food additive Sorbitol has an E-number E420 and is categorized as a sweetener, emulsifier and humectant.

Sorbitol is also used as a non-stimulant laxative. It is either an oral suspension or a suppository. It draws water into the large intestine, stimulating bowel movements.