The Short Answer
Sugar alcohols are low-calorie sweeteners derived from sugars and starches, added to protein bars to reduce the sugar count without using real sugar. They're generally recognized as safe, but many people experience digestive side effects — bloating, gas, and loose stools — especially in the quantities found in a single protein bar. If you've ever eaten a bar and felt off an hour later, sugar alcohols are the likely culprit.
What Exactly Are Sugar Alcohols?
Despite the name, sugar alcohols are neither sugar nor alcohol. They sit in a chemical middle ground — their structure resembles both, which is how they got the name. Maltitol, sorbitol, xylitol, erythritol, and isomalt are the most common ones you'll find on a protein bar label.
They provide fewer calories than sugar (roughly 0.2 to 3 calories per gram versus 4 for sugar) and cause a slower, smaller rise in blood glucose. For bar manufacturers, that's a useful combination: the product tastes sweet, the sugar line on the nutrition label stays low, and the net carb count looks favorable for keto-adjacent shoppers.
From a formulation standpoint, they also function as humectants — they help bars stay soft and extend shelf life. That's a practical reason they're in so many products, not just a sweetener play.
Why They're So Common in Protein Bars
Protein bar marketing runs on macros. A bar that says "20g protein, 5g sugar" looks clean on a shelf tag or a social media graphic. Sugar alcohols make that math possible without using artificial sweeteners like sucralose or aspartame, which carry their own label baggage.
Maltitol in particular is popular because it behaves most like sugar in terms of texture and sweetness, but it's also the sugar alcohol most associated with digestive distress. It has a glycemic index of around 35 — low compared to table sugar at 65, but not zero. Some labels subtract maltitol entirely from net carb calculations, which is technically incorrect under stricter accounting.
The result is a product that looks leaner than it is, and feels worse than it should.
The Gut Issue Is Real
Sugar alcohols are only partially absorbed in the small intestine. The unabsorbed portion travels to the large intestine, where gut bacteria ferment it. That fermentation produces gas. At small doses, most people tolerate this without noticing. At the doses common in protein bars — sometimes 15 to 20 grams per serving — many people don't.
The FDA doesn't require a specific warning on labels for sugar alcohols, though some manufacturers add "excess consumption may have a laxative effect" in small print. If you're eating a bar pre-workout or mid-afternoon in a meeting, that's not a footnote you want to find out about the hard way.
Erythritol is generally better-tolerated than maltitol or sorbitol because more of it gets absorbed before reaching the colon, but the individual response varies enough that it's not a universal fix.
How Sugar Alcohols Hide on Labels
The label math worth understanding:
Total carbohydrates includes everything — fiber, sugar, sugar alcohols, starch.
Net carbs (not an FDA-defined term) is typically calculated as:
Total carbs − fiber − sugar alcohols = net carbs
Brands use this calculation to market a bar as "only 4g net carbs" while the total carbohydrate line reads 25g. For people actively managing blood glucose, this shortcut can be misleading — especially with maltitol, which does affect blood sugar.
If you're a label reader, look for the sugar alcohol line under "Total Carbohydrates." It's required to be listed if sugar alcohols are present, though it often sits in a smaller font than the net carb callout on the front of the package.
What We Do Instead
At Genesee, we didn't build our bars around a macro number we needed to reverse-engineer. We started with whole-food ingredients and let the label reflect reality.
No sugar alcohols. No artificial sweeteners. No seed oils. The sweetness in our bars comes from real food sources, and the fat comes from grass-fed bison tallow — an ingredient with a longer track record than most food-science additives.
We're former NJCAA athletes. We ate a lot of bars that made us feel worse than nothing would have. That's a real and specific frustration, and it's the reason we built something different. You can read more about where Genesee came from on our story page.
The Comparison You Should Make at the Shelf
Next time you pick up a protein bar, run through this quick check:
- Find the sugar alcohol line under Total Carbohydrates.
- Identify which sugar alcohol — maltitol is the most problematic for digestion and blood glucose response; erythritol is milder.
- Check the amount — anything above 10g in a single serving is worth noting if you have a sensitive gut or are watching glycemic impact carefully.
- Compare it to the front-panel net carb claim — if those numbers don't add up intuitively, the brand is doing math that benefits their marketing, not your understanding.
This isn't about alarm. Sugar alcohols aren't toxic. But they're also not inert, and the current convention of treating them as nutritionally invisible is sloppy at best and misleading at worst.
For a direct side-by-side on how Genesee stacks up against other bars on sweeteners and ingredients, see our comparison page.
Who This Matters Most For
Athletes and active people: If you're using a bar for pre- or intra-workout fuel, digestive discomfort at the wrong time is more than an inconvenience. Whole-food ingredients that your gut recognizes tend to process more predictably.
Parents buying bars for kids: Children are more sensitive to the laxative effects of sugar alcohols by body weight. A bar that's fine for a 190-pound adult can cause real discomfort for a 70-pound kid eating it as an after-school snack.
Label readers: If ingredient transparency is part of how you shop, sugar alcohols are a case study in how brands optimize labels for the shelf, not for clarity. Understanding the mechanic makes you a sharper buyer across the whole category.
People monitoring blood glucose: Net carb math that subtracts maltitol is not honest accounting. If you're actively managing how food affects your blood glucose, the full carbohydrate picture — not the branded net carb number — is what matters.
The Bottom Line
Sugar alcohols are legal, common, and functional — but they come with real tradeoffs that most protein bar labels don't communicate clearly. Partial gut absorption causes digestive side effects in a significant portion of users. The net carb shorthand that omits them can misrepresent a product's true carbohydrate load. And for a category that sells itself on clean nutrition, leaning on processing aids to hit a marketing number is worth questioning.
If you want to see what a bar looks like when the ingredient list comes first, browse our products — or try a subscription and give your gut something it won't have to argue with.