Maltitol explained: Does the sugar-free sweetener spike glucose?

If you’ve ever picked up a “sugar-free” chocolate bar, a keto-friendly biscuit or a protein bar and wondered how it can taste sweet without any sugar in it, the answer is often maltitol. It’s one of the most common sweeteners you’ve never heard of – used in thousands of products on UK supermarket shelves, and doing a lot of the heavy lifting behind the “no sugar added” label.

Maltitol isn’t sugar, but it isn’t calorie-free or sugar-free either. It’s cheaper and sweeter than most alternatives, which is why it’s everywhere – and it can still raise your blood sugar and upset your stomach in ways the label won’t tell you.

This guide covers what maltitol actually is, why it’s in so many things, what it does in your body, and who should think twice before eating it.

So what is maltitol?

Maltitol is a sugar alcohol – not an alcohol you drink, but a type of carbohydrate that sits chemically between a sugar and a fibre. Chemists call this family polyols. You’ve probably eaten several of them without realising: erythritol, xylitol, sorbitol, isomalt and maltitol all belong to the same club.

They exist because food manufacturers wanted something that tastes and behaves like sugar without all the calories or blood-sugar impact. Maltitol is the one that comes closest to actual sugar. It’s around 75 to 90 per cent as sweet as the white stuff, has about half the calories, and – unlike most artificial sweeteners – behaves like sugar when you bake with it. That’s why it’s the go-to for sugar-free chocolate, sugar-free ice cream and anything that needs to feel indulgent.

The trade-off is that it isn’t quite as innocent as the “sugar-free” label implies.

How is it made?

Maltitol is made by taking maltose – a sugar found in starchy foods like corn or wheat – and running it through a chemical process called hydrogenation. That process converts the sugar into a sugar alcohol, which changes how your body handles it. Your gut only partially absorbs maltitol, which is why it delivers fewer calories than sugar – but also why it can cause the digestive issues we’ll get to shortly.

One quirk worth knowing: maltitol doesn’t brown or caramelise the way sugar does. That’s why sugar-free chocolate can taste right but sugar-free caramel usually doesn’t.

Does maltitol raise blood sugar?

Yes – and this is the bit most people get wrong. “Sugar-free” and “won’t raise blood sugar” are not the same thing.

Every food that affects blood sugar gets a glycaemic index (GI) score – a number from 0 to 100 that tells you how sharply it lifts your glucose. Table sugar sits around 60 to 65. Pure glucose is 100. Sweeteners like sucralose or erythritol are near zero – they barely register.

Maltitol lands at roughly 35 . Lower than sugar, but a long way from zero – and higher than most other sugar alcohols. Which means a “sugar-free” chocolate bar sweetened with maltitol can still nudge your glucose up, and eating two or three of them in an afternoon starts to look uncomfortably close to eating the sugar version.

A 2021 review of sugar alcohols confirmed the pattern: polyols generally blunt the glycaemic response compared with sugar, but maltitol’s effect is modest, not absent. If you’re managing diabetes, insulin resistance or you’re just trying to keep your glucose stable, maltitol should be counted as a carbohydrate – not treated as a free food.

A continuous glucose monitor makes this visible in a way a label can’t. One caveat worth flagging: Ultrahuman’s database holds very few logged instances of maltitol consumed on its own, so the picture here draws on published research rather than original Ultrahuman data. But the practical takeaway holds – if you want to know how a specific maltitol product affects you, testing it against a baseline with a CGM tells you more than any packet will.

Why it upsets your stomach

The other complaint people have about maltitol is what it does south of the ribcage. Gas, bloating, cramping, and at higher doses, loose stools.

The reason is mechanical. Your small intestine can only absorb some of the maltitol you eat. The rest travels down into your colon, where two things happen: gut bacteria ferment it (producing gas), and it pulls water into the bowel by osmosis (loosening things up). At small doses your gut copes fine. At large doses – or in people with sensitive digestion – it doesn’t.

That said, maltitol’s laxative reputation is a bit overblown. In a controlled trial, 40 grams of maltitol in chocolate caused only mild gas and rumbling with no significant laxative effect , and was better tolerated than the same dose of isomalt or lactitol. The horror stories usually come from very high intakes, individual sensitivity, or products that combine maltitol with more aggressive sugar alcohols like sorbitol.

In the EU, foods high in added polyols have to carry a label warning that excessive consumption may have a laxative effect. That’s not scaremongering – it’s just useful information the manufacturers would rather you didn’t dwell on.

How much is too much?

There’s no single threshold, because tolerance is highly individual and builds with regular exposure. Many people tolerate 20 to 40 grams a day fine. A sensitive person may react to a fraction of that. And here’s the thing – a single sugar-free chocolate bar can easily contain 20 grams of maltitol on its own.

Practical signs you’ve overdone it: gurgling within a couple of hours, bloating, and loose stools. The fix is straightforward. Cut the portion. Tolerance often improves if you build up slowly rather than eating a whole bar on day one.

How it compares to other sugar alcohols

Not all sugar alcohols behave the same way. They differ in sweetness, glycaemic impact and how well the gut tolerates them.

Approximate values compiled from polyol research (Livesey 2003; Msomi 2021); individual response varies.

Erythritol stands out because it’s almost entirely absorbed and excreted unchanged, so it has essentially no glycaemic impact and causes far less digestive upset than maltitol. If a product’s main goal is to avoid both blood-sugar impact and stomach trouble, erythritol is usually the better choice – maltitol’s advantage is that it behaves more like sugar in cooking, so it wins on taste and texture but loses on the metabolic side.

One aside worth knowing: xylitol is highly toxic to dogs even in tiny amounts. Keep xylitol-sweetened products away from pets.

Who should be careful with maltitol?

Maltitol is recognised as safe by regulators including the FDA and EFSA, and for most people the main issue is comfort, not danger. A few groups have more reason to watch their intake:

• People managing diabetes or blood sugar. Maltitol’s glycaemic index isn’t trivial, so “sugar-free” doesn’t mean “won’t affect glucose.” Count it toward your carbohydrate intake and, ideally, see how your own body responds.
• Anyone with IBS or a sensitive gut. Sugar alcohols are fermentable carbohydrates (the “P” in the low-FODMAP framework), so maltitol can be a strong trigger for bloating and diarrhoea.
• People following a ketogenic diet. Maltitol’s absorbed portion still provides usable carbohydrate, so it can affect ketosis more than labels suggest. Many “net carb” counts understate its impact.
• Children. Smaller bodies reach the laxative threshold faster, so sugar-free sweets can cause diarrhoea in kids at modest amounts.

If you already track elevated glucose outside of a diabetes diagnosis, Ultrahuman’s explainer on non-diabetic hyperglycaemia is a useful next read, and the guide to the types of sugar covers how maltitol fits among other sweeteners.

This article is for informational purposes and isn’t medical advice. People managing diabetes, IBS or any digestive or metabolic condition should work with a clinician for individual guidance. Disclosure: Ultrahuman sells the M2 Live CGM, Ring AIR and Ring PRO referenced in this guide.