“Sugar-free” – still a blood-sugar rise? The thing with maltitol & IMO

The first trap: not every sugar alcohol is the same

Evidence level: established

“Sugar-free” sweets are usually sweetened with sugar alcohols (polyols). But this group is anything but uniform. Some barely raise blood sugar at all – others quite noticeably. What matters is the glycaemic index (GI), which indicates how much a substance raises blood sugar (0 = no rise, 100 = pure glucose).

The much-cited scientific reference (Livesey, 2003) shows the range clearly: erythritol 0, mannitol 0, sorbitol 9, isomalt 9, xylitol 13 – but maltitol 35, and maltitol syrup even around 39.¹ For comparison: table sugar is 65. Maltitol thus has the highest GI of all common sugar alcohols – roughly half as high as sugar.² Particularly relevant: this value applies largely regardless of the amount consumed and the metabolic state (including in type 1 and type 2 diabetes).¹

Concretely with ahead: erythritol yes, but not everywhere

A fair look at the products shows a mixed picture. Many ahead products (such as the gummy bears or various candy bars) use erythritol – which is consistent, because erythritol has a GI of practically 0 and is therefore genuinely very blood-sugar-friendly.³

Other products from the same brand, however, are sweetened with maltitol. For the “Dark Choco Chunks”, for example, the ingredients list is simply: cocoa mass, sweetener maltitol, cocoa butter, emulsifier.⁴ Several bars also contain maltitol, sometimes combined with sorbitol and isomalt.⁴ ahead itself correctly notes for the Chunks that maltitol “raises blood sugar less than sugar” – that’s true, but it’s not the same as “doesn’t raise blood sugar”.⁴

The second trap: what “sugar-free” actually means legally

Evidence level: established (EU law)

Here lies the real point of clarification. Under the EU Health Claims Regulation, “sugar-free” refers exclusively to classic sugar (mono- and disaccharides) and means: at most 0.5 g of sugar per 100 g.⁵ “No added sugar” merely means that no table sugar or sweetening ingredient was added – natural sugar (e.g. from milk) may be present.⁵

The crucial catch: sugar alcohols like maltitol legally count as sweeteners, not as sugar. They therefore don’t appear in the “of which sugars” row of the nutrition table at all – even though they can raise blood sugar.⁶ A product can thus quite rightly be called “sugar-free” and show a low number in the “of which sugars” row – and still raise blood sugar noticeably via maltitol.

The third trap: “fibre” that isn’t (IMO)

Evidence level: well documented

Besides the sweetening sugar alcohol, it’s worth a second look at the ingredients listed as “fibre” – especially IMO (isomalto-oligosaccharides). It appears above all in “high-fibre” and “low-carb” bars, often at more than 15 g per bar.⁷ And it’s a prime example of how a technically correct declaration can still mislead.

The background: whether a carbohydrate counts as “fibre” is often tested in the lab via a fungal enzyme. This enzyme can barely split IMO – so IMO appears indigestible in the test and may be listed as fibre.⁸ But the human digestive enzymes in the small intestine break IMO down largely into glucose – just more slowly than normal sugar.⁸ Studies confirm this: after IMO, blood sugar and insulin rose measurably, unlike after genuine soluble fibre.⁷ The authors of a comparative study therefore state explicitly that IMO is not a fibre but a slowly digestible carbohydrate.⁷

And then there’s digestion

A second, very practical drawback of maltitol (and other polyols in larger amounts): they can be laxative and cause bloating.² In the EU, products with more than 10 g of certain sugar alcohols per 100 g must even carry a warning about the possible laxative effect.² Anyone who eats a whole bar of “sugar-free” chocolate may feel that distinctly.

Practical tips:

• Read the ingredients list, not just the front. If “maltitol” or “maltitol syrup” is listed, caution is warranted if you’re blood-sugar-sensitive.
• Erythritol, mannitol (GI 0) are blood-sugar-friendly; sorbitol, isomalt, xylitol (GI 9–13) usually little problem; maltitol (GI 35) is the exception.
• Watch the “fibre” too. If “IMO” or “isomalto-oligosaccharides” is in the list, treat the “net carb” figure with caution.
• Test for yourself. If you use a CGM or meter, check your individual response – it varies from person to person.
• With diabetes or insulin therapy, discuss counting these with your care team.