Sugar Alcohols and Keto: What You Need To Know
How they can affect ketosis, blood sugar, and digestion.
By KetoPeek Updated
The short version
Sugar alcohols are sweeteners found in most keto-labeled snacks and protein bars. Most of them raise blood sugar less than regular sugar, but they're not all the same.
Individual tolerance varies, and larger amounts can cause digestive trouble even with the gentler ones.
Quick reference
Erythritol
- Glycemic index
- ~0
- Stomach
- Gentle
Xylitol
- Glycemic index
- ~13
- Stomach
- Moderate
Sorbitol
- Glycemic index
- ~9
- Stomach
- Moderate
Isomalt
- Glycemic index
- ~9
- Stomach
- Rough
Lactitol
- Glycemic index
- ~6
- Stomach
- Rough
Mannitol
- Glycemic index
- ~0
- Stomach
- Rough
Maltitol
- Glycemic index
- ~35
- Stomach
- Moderate
HSH / polyglycitol
- Glycemic index
- ~39
- Stomach
- Rough
| Sugar alcohol | Glycemic index | Cal / g | Stomach | Keto fit |
|---|---|---|---|---|
| Erythritol | ~0 | 0.2 | Gentle | Excellent |
| Xylitol | ~13 | 2.4 | Moderate | Good |
| Sorbitol | ~9 | 2.6 | Moderate | Good |
| Isomalt | ~9 | 2.0 | Rough | Caution |
| Lactitol | ~6 | 2.0 | Rough | Caution |
| Mannitol | ~0 | 1.6 | Rough | Caution |
| Maltitol | ~35 | 2.1 | Moderate | Avoid |
| HSH / polyglycitol | ~39 | 3.0 | Rough | Avoid |
Glycemic index compares foods to glucose (100). Table sugar is 65. Lower is better for keto.
What are sugar alcohols?
Despite the name, they're neither alcohol nor sugar. They're a class of carbohydrate used as sweeteners. On ingredient labels you'll usually spot them by names ending in "-ol": erythritol, xylitol, sorbitol, maltitol, and so on.
Manufacturers use them because they taste sweet but carry fewer calories and tend to cause a smaller blood sugar response than regular sugar. You'll find them in protein bars, sugar-free candy, keto desserts, and low-carb baked goods.
Do they affect ketosis?
For most people, the news is pretty good. Most polyols produce a smaller insulin and glucose response than sugar, so they're unlikely to knock you out of ketosis the way a regular carb would. That said, individual response varies, and no sweetener is completely free.
Erythritol is the standout. Most of it is absorbed and excreted without being metabolized, so its glycemic impact is very low for most people.
Xylitol and sorbitol are somewhere in the middle. They have a modest effect compared to sugar, but they're not a free pass.
Maltitol is the one to watch. Its glycemic index is meaningfully higher than erythritol or xylitol. On strict keto, most people either count it like a regular carb or avoid it altogether.
Watch your stomach
Not all sugar alcohols get fully absorbed. What passes through moves to the colon, where bacteria ferment it. That can mean gas, bloating, or diarrhea if you have too much in one sitting.
Most adults handle roughly 10–15 g a day without trouble. Past 20–30 g in one sitting, symptoms are much more common. Some sugar-free products pack a surprising amount per serving, so it's worth checking the label before you eat the whole bag.
If you have IBS or follow a low-FODMAP diet, your tolerance is likely lower than average. Start small and pay attention to how you feel.
How Keto Peek treats sugar alcohols
When a label lists sugar alcohols, we don't just subtract them all from carbs. We weight each type based on how much it actually affects blood sugar. When we can read the ingredient list, we split the total across the specific sweeteners we detect. If we can't tell which ones are in there, we default to the conservative end so most of those grams still count.
Minimal impact (mostly excluded)
Erythritol, allulose, monk fruit, mannitol, tagatose, isomalt, lactitol
→ Counted as ~0–10% carbs
Moderate impact (partially counted)
Xylitol, sorbitol, glycerin (glycerol), HSH
→ About 50–55% counted as carbs
High impact (mostly counted)
Maltitol
→ Powder: ~75% counted
→ Syrup: 100% counted
Going deeper
The science, if you are curious
How are sugar alcohols metabolized?+−
Every polyol takes a different path through your body. Erythritol is the unusual one: most of it is absorbed in the small intestine, circulates briefly, and gets excreted in urine with almost no metabolism. That's why its calorie and glycemic impact is so low.
Most others are only partially absorbed. What doesn't get absorbed moves to the colon, where bacteria ferment it. That fermentation produces some calories (roughly 1.6–2.6 kcal per gram, depending on the polyol) and is the main reason they can cause digestive symptoms at higher doses.
Lactitol and isomalt are poorly absorbed and heavily fermented, so they tend to be easy on blood sugar but harder on the gut for some people.
What does research say about blood sugar and insulin?+−
Studies like Livesey (2003) looked at the glycemic and insulin indices of polyols. Erythritol consistently scores very low. Maltitol scores higher, and while it's still below table sugar in most comparisons, it's high enough that people on strict keto tend to treat it carefully.
Individual responses vary. Your own blood sugar data, if you track it, is more useful than any published table average.
Are sugar alcohols safe over the long term?+−
Common polyols are generally considered safe by major regulators at typical intake levels. EFSA has set acceptable daily intake values for some of them, including erythritol, based on body weight.
Some recent observational research has linked elevated blood levels of certain polyols to cardiovascular markers, but that work is early and doesn't establish cause and effect. For most people, the main practical concern remains digestive tolerance at high doses, not long-term safety.
How do I read sugar alcohols on a label?+−
In the US, sugar alcohols are listed under total carbohydrates, separate from "sugars." The ingredient list should tell you which specific polyol was used. That detail matters, because they're not interchangeable from a keto standpoint.
"Sugar-free" on the front of a package doesn't mean "carb-free." Check the actual grams. If maltitol or HSH appears near the top of the ingredient list, it's worth a closer look if you're strict keto.