The warning follows the cases of two patients who suffered chronic diarrhoea, abdominal pain and severe weight loss after ingesting large amounts of sorbitol.

Writing in the British Medical Journal, the doctors from Berlin said the patients - a man and a woman - had consumed some 15 to 20 sticks of chewing gum a day. When they kicked the habit, both regained normal bowel function.

Sorbitol, also known as E420, is poorly absorbed by the small intestine and is known to have laxative properties. But Dr Juergen Bauditz and colleagues of the University of Berlin said many consumers might fail to link it with their gastrointestinal problems.

'Our cases demonstrate that sorbitol consumption can cause not only chronic diarrhoea and functional bowel complaints but also considerable unintended weight loss - about 20 per cent of usual body weight,' they wrote. -- REUTERS