Sugar alcohols and the tolerance problem nobody warns you about

Sugar alcohols are the reason a bar can claim two grams of sugar and still taste sweet. They are also the single most common reason someone tells us a bar "did not agree with them."

The category name hides real differences. These are four distinct compounds with different absorption, different sweetness, and very different tolerance thresholds.

They are poorly absorbed by design

That is the point. A sweetener that passes through largely unabsorbed contributes fewer calories and less glucose. The unabsorbed fraction continues into the large intestine, where gut bacteria ferment it. Fermentation produces gas. Enough unabsorbed material also draws water into the bowel osmotically.

This is not an allergy or a sensitivity. It is the expected behaviour of the ingredient, and it scales with dose.

The thresholds are not the same

Sorbitol is poorly tolerated at relatively low intakes, which is why US labels carry a laxation warning above a defined daily amount. Maltitol is better tolerated than sorbitol but is also the least "free" of the group metabolically — its glycaemic impact is meaningfully higher than the others, which undercuts the reason many people choose it.

Xylitol sits in between. Erythritol is the outlier: most of it is absorbed in the small intestine and excreted unchanged in urine, so comparatively little reaches the colon to ferment. That is why erythritol is generally the best tolerated of the four, and why it displaced the others in a lot of formulations.

Why bars use blends

A bar rarely contains one sugar alcohol. Blending lets a formulator hit a sweetness and texture target while keeping any single compound under the level where people notice a problem — and, on the label, splits one sweetening system across several lines that each fall further down the ingredient list.

That is worth knowing when you compare two products. The bar with maltitol syrup fifth is not necessarily using less of it than one with maltitol third.

What actually resolves the question

"Is this bad for you" does not resolve. "How much of this can I eat before it causes a problem, and how does that compare to what is in this bar" does.

That number is different per compound and different per person, and the honest answer for most people is that it takes one uncomfortable afternoon to learn. What the reports here can tell you is which compound you are dealing with, what intake the regulators assessed, and what the documented effects are.

You can search any sweetener or text the ingredient to Iggy and get the same summary back.