Why do sugar free sweets carry a laxative warning?

Turn over a bag of sugar free sweets and you will usually find a warning that excessive consumption may produce laxative effects. It is not a joke or an overcautious lawyer's idea. It is the law, and it is there because the sweeteners in sugar free sweets really can send you running.

Sweeteners your gut cannot finish

Most sugar free sweets are made with sugar alcohols, also known as polyols, such as maltitol, sorbitol, isomalt and xylitol: see what are sugar free sweets made with?

Unlike sugar, sugar alcohols are usually only partly absorbed in the small intestine. That is useful, because it means they have less effect on blood sugar. But what is not absorbed carries on to the large intestine. Like many substances the body cannot fully digest, eating too much can lead to bloating, diarrhoea and wind. Some people notice effects even after a single serving, though most people build up some tolerance if they eat them regularly.

Some sugar alcohols are strong enough to be used as medicine. Sorbitol is sold over the counter as a laxative to treat constipation, and maltitol is also used as one.

How much is too much?

It depends on the sweetener and the person, but the figures give an idea.

• Maltitol typically causes diarrhoea at more than about 90 g a day, and around 40 g can cause mild rumbling and wind.
• Xylitol was the subject of a 1985 report by the European Scientific Committee on Food, which said that 50 g a day can cause diarrhoea.
• Erythritol is the exception. Most of it is absorbed in the small intestine and passed out unchanged, so in small doses it does not normally cause laxative effects. Even so, in 2023 the European Food Safety Authority set a recommended daily limit of 0.5 g per kilogram of body weight, about 35 g for an average adult, to guard against its laxative effect.

What the law says

Under UK food labelling law, which carried over the European rules, any food containing more than 10 per cent added polyols must carry the words excessive consumption may produce laxative effects. Products sweetened with intense sweeteners must also say with sweetener next to their name, and those with aspartame must say they contain a source of phenylalanine.

The Haribo saga

A bag of gummy bears showed why the warning matters. Haribo's sugarless gummy bears, sold in five pound bags on Amazon in the United States, were sweetened with Lycasin, a syrup based on maltitol. In early 2014 the product's reviews went viral, as buyer after buyer described in vivid and often very funny detail what had happened after eating a large number of them. One reviewer called it gastrointestinal Armageddon.

The product page carried a notice that consumption of some sugar free candies may cause stomach discomfort and a laxative effect. As Refinery29 pointed out at the time, the label did not say how much maltitol each serving contained, which made it hard for buyers to judge how many was too many. The American Dietetic Association advises against eating more than 20 g of maltitol at a time.

The sensible answer

Read the warning, go easy on large bags, and keep them well away from dogs, because xylitol is poisonous to them: see can dogs eat sweets?

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