In this week's BMJ, doctors warn of excess sorbitol intake, a widely used sweetener in "sugar-free" products such as chewing gum and sweets.

Sorbitol has laxative properties and is poorly absorbed by the small intestine.

Their advice follows the cases of two patients with chronic diarrhoea, abdominal pain and severe weight loss. Although extensive investigations were carried out, final diagnosis was only established after detailed analysis of eating habits.

On questioning, both patients admitted consuming substantial amounts of sugar-free gum and sweets.

The first patient (a 21 year old woman) chewed large amounts of sugar-free gum, accounting for a total daily dose of 18-20g sorbitol (one stick of chewing gum contains about 1.25g sorbitol). The second patient (a 46 year old man) reported chewing 20 sticks of sugar-free gum and eating up to 200g of sweets each day, which together contained around 30g sorbitol.

After both patients started a sorbitol free diet, diarrhoea subsided, normal bowel movements resumed and weight gain was achieved.

As possible side effects are usually found only within the small print on foods containing sorbitol, consumers may be unaware of its laxative effects and fail to recognise a link with their gastrointestinal problems, write the authors.

In conclusion, they say, our cases demonstrate that sorbitol consumption can cause not only chronic diarrhoea and functional bowel complaints but also considerable unintended weight loss (about 20% of usual body weight). Thus, the investigation of unexplained weight loss should include detailed dietary history with regard to foods containing sorbitol.

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