Sorbitol, also known as E 420, can trigger severe weight loss, abdominal pain and diarrhoea.

A report in the British Medical Journal today highlights the cases of patients who lost up to a fifth of their bodyweight.

The cause was eventually traced to excess intake of sorbitol - one was eating 14-20 sticks of gum a day.

Dentists recommend chewing sugarfree gum to increase saliva production, which reduces cavities and strengthens teeth.

Wrigley, which owns many of the brands sold in the UK, has seen its sales in Europe grow by a third since Sorbitol is also used in sugar-free sweets, some cereals and foods aimed at diabetics.

But gastroenterology experts in Germany say many consumers - and even some doctors - are unaware of the laxative side-effects of sorbitol, which can also hinder the absorption of nutrients into the small intestine.