You see them on every protein bar label: erythritol, maltitol, sorbitol, xylitol. They're called sugar alcohols, and they're the reason a bar can taste sweet while claiming "1g sugar" or "sugar-free." But not all sugar alcohols are equal — some are genuinely harmless, while others spike your blood sugar and wreck your digestion.
Here's everything you need to know about sugar alcohols in protein bars: what they are, which ones are safe, which ones to avoid, and why your stomach sometimes hates them.
Sugar alcohols (polyols) are a category of sweeteners that are chemically similar to both sugar and alcohol — but they're neither. They don't contain ethanol (you won't get drunk), and they're not sugar (they're processed differently by your body).
They occur naturally in small amounts in fruits and vegetables. The sugar alcohols in protein bars are produced industrially, usually from corn starch or birch wood, through a hydrogenation process.
Sugar alcohols provide sweetness with fewer calories than sugar and less blood sugar impact. That's why protein bar manufacturers love them — they can make bars taste sweet while keeping the "sugar" line on the nutrition label low.
Under FDA labeling rules, sugar alcohols are listed under "Total Carbohydrates" but NOT under "Sugars." This is why a bar can contain 15g of sugar alcohols and still say "1g sugar" — the sugar alcohols aren't technically "sugars" by regulatory definition.
This labeling creates confusion. Many people see "1g sugar" and assume the bar has minimal sweetener impact. But if that bar contains 15g of maltitol, you're getting 75% of the glycemic response you'd get from actual sugar. The "1g sugar" label is technically accurate but practically misleading.
Erythritol is the gold standard of sugar alcohols. Zero calories, zero glycemic impact, and minimal digestive issues because it's absorbed before reaching your large intestine (where fermentation causes gas and bloating). Built Bar uses erythritol as its primary sweetener.
The only downside: a mild "cooling" sensation on the tongue that some people notice.
Allulose is technically a rare sugar, not a sugar alcohol, but it functions similarly. It tastes the closest to real sugar of any alternative sweetener — no aftertaste, no cooling effect, no bitterness. It's increasingly used in premium protein bars.
The FDA ruled in 2019 that allulose doesn't need to be listed as "sugar" or "added sugar" on nutrition labels, because it contributes virtually no calories and doesn't raise blood sugar.
Xylitol is less common in protein bars than erythritol but shows up occasionally. It has documented dental health benefits (reduces cavity-causing bacteria). The main concern: it's toxic to dogs. If you share snacks with a pet nearby, xylitol-containing bars need careful handling.
Sorbitol draws water into the large intestine, which is why it's literally used as a medical laxative. In protein bars, even 10-15g can cause bloating, cramping, and diarrhea in sensitive individuals. It's less common in modern bars as manufacturers shift to better-tolerated options.
Maltitol is the sugar alcohol you should actively avoid. Despite being marketed as a "sugar-free" sweetener, it spikes blood sugar at 75% of sugar's rate — making it nearly useless for diabetics or keto dieters. It also causes notorious digestive issues: bloating, gas, and diarrhea.
Why do bars use it? Because it's cheap, it tastes closest to sugar, and it creates good texture. think! and some Barebells flavors contain maltitol, though in controlled amounts.
This matters enormously for diabetics, keto dieters, and anyone managing blood sugar:
Many keto-focused resources tell you to subtract all sugar alcohols from your carb count. This is only accurate for erythritol and allulose. If your bar contains maltitol, you should count at least half of those grams as effective carbs.
For bars optimized for blood sugar management, see our best protein bars for diabetics guide.
The mechanism is simple: most sugar alcohols (except erythritol) aren't fully absorbed in your small intestine. The unabsorbed portion reaches your large intestine, where gut bacteria ferment it — producing gas, bloating, and drawing water into the bowel (causing loose stools).
Your tolerance depends on:
Not all sugar alcohols are the same. Erythritol and allulose are genuinely excellent sweeteners — zero calories, zero glycemic impact, and minimal digestive issues. Maltitol and sorbitol are problematic — they spike blood sugar more than advertised and cause digestive distress.
When evaluating a protein bar, don't just check the sugar content — check which sugar alcohol is providing the sweetness. A "0g sugar" bar sweetened with erythritol is legitimately sugar-free. A "0g sugar" bar sweetened with maltitol is hiding a blood sugar spike behind a technicality.
For a full guide on evaluating protein bar labels, see our how to read a protein bar label guide. For the best sugar-free options, see best sugar-free protein bars of 2026.
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