Quick Answer: Sugar alcohols like erythritol, maltitol, and sorbitol — common in low-sugar protein bars — are poorly absorbed by the gut and ferment in the colon, causing gas, bloating, and sometimes diarrhea, especially above roughly 20-30g in one sitting.

You eat one protein bar and feel fine. Two bars, or one particular brand, and you’re uncomfortably bloated an hour later. That’s not an allergy or intolerance in the usual sense — it’s a well-documented ingredient effect.

Why do sugar alcohols specifically cause digestive issues?

Sugar alcohols (erythritol, maltitol, sorbitol, xylitol) are only partially absorbed in the small intestine. The unabsorbed portion travels to the colon, where gut bacteria ferment it — producing gas as a direct byproduct, along with drawing extra water into the intestine, which is what causes the bloating and, at higher amounts, diarrhea.

This is a normal, expected mechanism, not a sign something’s wrong with your gut — some sugar alcohols (like erythritol) cause this less than others (maltitol and sorbitol are generally the worst offenders).

How much sugar alcohol actually triggers symptoms?

Individual tolerance varies, but general reporting suggests symptoms often start appearing above 20-30g of sugar alcohols in one sitting for many people — and a single protein bar loaded with maltitol can pack 15-20g on its own, meaning two bars easily crosses that threshold.

Check the label: sugar alcohols are listed separately from total sugar, often as ‘sugar alcohol’ or by name (maltitol, erythritol, etc.) under the total carbohydrate line.

What Nobody Tells You About High-Protein Labels

Here’s the part that surprises people: a bar marketed as ‘low sugar’ or ‘keto-friendly’ is often the exact one causing the problem — sugar alcohols are frequently used specifically to hit a low-sugar claim while keeping the bar sweet, meaning the healthier-sounding label can correlate with more digestive trouble, not less.

A bar with moderate real sugar and no sugar alcohols may actually sit better in your stomach than one boasting ‘1g sugar’ loaded with 18g of maltitol.

FAQ: Protein Bar Digestion Questions, Answered

Which sugar alcohol is gentlest on digestion?

Erythritol is generally better tolerated than maltitol or sorbitol at equivalent amounts, since a larger portion of it is absorbed before reaching the colon.

Can I build tolerance to sugar alcohols over time?

Some people report modestly improved tolerance with gradual, consistent exposure, though it varies a lot individually — starting with smaller amounts is a reasonable approach either way.

Are sugar alcohols unsafe, or just uncomfortable?

For most people they’re a digestive comfort issue, not a safety issue, though very high intakes can cause more significant GI distress. This is general information, not medical advice.

TL;DR:

• Sugar alcohols (maltitol, sorbitol, erythritol) ferment in the colon, causing gas and bloating
• Symptoms often appear above 20-30g in one sitting — easy to hit with 2 bars
• ‘Low sugar’ labels often mean more sugar alcohol, not less digestive risk
• Erythritol is generally gentler than maltitol or sorbitol at similar amounts

Next bloating episode, flip the wrapper over and check the sugar alcohol line before blaming the protein.