What are sugar alcohols? No booze, and not quite sugar either

A misleading name: won't get you tipsy, and not quite as sweet as sugar

Scientists call this group polyols. In everyday English, they're sugar alcohols.

The word "alcohol" here is chemist's language. It refers to a small attachment on the molecule, a bit like a "hook" with its own name. Drinking alcohol (ethanol) has that same hook, hence the shared name. But the two are completely different things.

In shape, a sugar alcohol molecule looks a lot like sugar. Similar enough to touch your tongue and switch on the "sweet" light. But different enough that your body handles it in its own way.

Who's in the sugar alcohol family?

It's a fairly big family. You'll meet them on labels for candy, biscuits and chewing gum:

Then there's erythritol, a name you'll often see in sweetener blends.

A cute fun fact: prunes are famous for keeping things moving, partly thanks to the sorbitol naturally found in the fruit. Nature was using sugar alcohols long before factories started making candy.

Why can lots of sugar free candy upset your tummy?

This is the part many people learn by experience.

When you eat white sugar, your small intestine absorbs almost all of it. But with sugar alcohols like sorbitol, maltitol and xylitol, the small intestine only absorbs part. The rest travels on to the large intestine.

Two things happen there:

1. It pulls water into the gut. Like sprinkling salt on cucumber slices, water gets drawn out. More water in the gut means looser stools.
2. Gut bacteria ferment it. That process makes gas. Your belly starts to feel tight and gurgly.

A few candies are usually fine. But eat a whole bag of candy or a whole maltitol chocolate bar at once, and many people feel bloated and gassy, and sometimes need to make a dash for the bathroom.

That's why, in Europe, products with more than 10% added polyols must print a warning: excessive consumption may produce laxative effects. Everyone's tolerance is different, and the body usually gets used to small amounts eaten regularly.

Fewer calories than sugar, but not always zero

Because they're only partly absorbed, most sugar alcohols provide fewer calories than white sugar.

Under EU labeling rules:

• Sugar and starch: 4 calories per gram.
• Most sugar alcohols: counted at 2.4 calories per gram.

So a "sugar free" chocolate bar made with maltitol still has calories. Not as few as many people think.

As for blood sugar: sugar alcohols usually raise it more slowly and less than white sugar does. How much depends on the type. Maltitol, for instance, still raises blood sugar noticeably more than its siblings.

Two fun facts about xylitol

• Mouth bacteria don't ferment xylitol the way they ferment sugar. That's why it so often shows up in chewing gum and toothpaste.
• Xylitol is highly toxic to dogs. Even a small amount is dangerous for them. If you have a pup at home, keep the gum well out of reach.

Frequently asked questions