What Are Sugar Alcohols? Why Your Protein Bar Is Making You Bloated

You eat clean. You train hard. You grab a protein bar because it says 20g protein on the front and sugar-free on the back. Thirty minutes later, you're bloated, gassy, and wondering what went wrong.

You're not alone. This is one of the most common complaints in the sports nutrition industry. And the culprit is almost always the same thing: sugar alcohols.

If you've ever flipped a protein bar over and seen words like maltitol, sorbitol, erythritol, or xylitol on the ingredient list, you've been eating sugar alcohols. Most people don't know what they are. And honestly, most brands are counting on that.

So let's break it down.

Sugar alcohols are a class of sweeteners that are neither sugar nor alcohol. Chemically, they're carbohydrates with a molecular structure that partially resembles sugar and partially resembles alcohol. That's where the confusing name comes from. They do occur naturally in small amounts in certain fruits and vegetables, but the sugar alcohols in your protein bar are industrially manufactured.

The ones you'll see most often in protein bars and "sugar-free" snacks include maltitol, sorbitol, erythritol, xylitol, and isomalt. Brands use them because they provide sweetness at roughly half the calories of regular sugar and they have a lower glycemic impact. That means a brand can print "low sugar" or "sugar-free" on the label while still keeping the bar sweet.

Sounds like a win on paper. But here's where it falls apart.

When you eat a protein bar loaded with sugar alcohols, your small intestine can only partially absorb them. The portion that doesn't get absorbed travels down to your large intestine, where your gut bacteria start fermenting it. That fermentation produces gas. At the same time, sugar alcohols are osmotic, which means they pull water into your intestine. Put those two things together and you get bloating, cramping, gas, and in higher doses, diarrhea.

This isn't a fringe issue or something that only affects a few unlucky people. This is especially true for people with IBS or sensitive digestion, but it affects plenty of otherwise healthy people too. Multiple meta-analyses have shown that reducing FODMAP intake, including polyols like sugar alcohols, leads to significant reductions in IBS symptom severity.

Not all sugar alcohols are equally bad. Maltitol and sorbitol are the worst offenders because they're poorly absorbed and aggressively fermented. Erythritol tends to be better tolerated since most of it gets absorbed in the small intestine before reaching the colon. But it's not completely in the clear for sensitive individuals either.

And here's the thing most people miss: a lot of protein bars don't just use one sugar alcohol. Many contain multiple types combined with other fermentable fibres like chicory root (inulin), which just makes everything worse.

One case documented by Poison Control involved a 12-year-old girl who had chronic abdominal pain and cramping several times a week. Lab results came back normal. Doctors couldn't find a cause. Eventually someone asked about her diet. Turned out she was regularly eating sorbitol-containing sugar-free products. When she stopped eating them, her symptoms went away completely.

That was a child eating sugar-free gum and diet bars. Now think about an adult consuming 15 to 20 grams of sugar alcohols in a single protein bar. Sometimes twice a day.

It comes down to two things: cost and marketing.

Sugar alcohols are cheap. They cost a fraction of what natural alternatives like monk fruit cost, and that's why the vast majority of "sugar-free" or "keto-friendly" bars rely on them. They make it easy for a brand to print impressive looking macros on the front of the pack. High protein, low sugar. The digestive trade-off gets buried in the ingredient list where most people never look.

Here's what usually happens. Someone buys a bar, likes the taste, maybe even leaves a good review. Then they get bloated two hours later and blame it on something they ate for lunch. The brand gets a five-star rating. Your gut gets punished. That cycle repeats every single day across the entire industry.

Every protein bar sold in Australia has to list ingredients in descending order by weight. Here's what to look for:

1.     Words ending in "-ol": maltitol, sorbitol, xylitol, erythritol, isomalt, mannitol, lactitol. If any of these show up, the bar contains sugar alcohols.

2.     Check the nutrition panel: if a bar has more than one sugar alcohol, you'll usually see "sugar alcohols" listed as a combined figure under carbohydrates. If there's only one type, it might just be listed by name.

3.     Look for "sugar-free" or "keto" claims: these are strong indicators that sugar alcohols are involved. A bar can't be sweet and truly sugar-free unless it uses sugar alcohols, artificial sweeteners, or a natural alternative like monk fruit or stevia.

Not every sweetener wrecks your gut. Monk fruit (also called luo han guo) is a natural, zero-calorie sweetener that comes from a small fruit grown in Southeast Asia. It gets its sweetness from antioxidant compounds called mogrosides, which are over 100 times sweeter than sugar. The FDA classifies it as Generally Recognised as Safe (GRAS). And unlike sugar alcohols, it doesn't ferment in your gut and doesn't pull water into your intestine. No bloating. No gas. No cramping.

So why don't more brands use it? Simple. Monk fruit is significantly more expensive than sugar alcohols. It's much easier and much cheaper to use maltitol syrup and let consumers deal with the side effects.

Stevia is another natural option, although a lot of people find it has a bitter aftertaste. For protein bars specifically, monk fruit tends to deliver a cleaner, more natural sweetness.

When we started developing The Volk Bar with Alexander Volkanovski, the very first decision we made was the one most brands avoid. Zero sugar alcohols. Not reduced. Not "minimal." Zero. No maltitol, no sorbitol, no erythritol. We went with monk fruit instead.

We use rice syrup as a structural ingredient to keep the bar soft on the shelf. Without it (or without sugar alcohols), protein bars go rock hard within days. It's not there as a sweetener. It's there because it was the honest alternative to the ingredient that makes every other bar cause problems.

Each Volk Bar delivers 17.5g of complete protein from an organic plant and whey blend, 5.1g of prebiotic fibre from tapioca that actually supports your gut instead of disrupting it, and a taste that doesn't require you to sacrifice your digestion for the next two hours.

We also deliberately chose soluble tapioca fibre over cheaper options like chicory root. Chicory root (inulin) is another common culprit behind bar-related bloating. Tapioca fibre feeds your beneficial gut bacteria without the aggressive fermentation.

COMPARISON

Sugar alcohols aren't evil. They have their place. But if you're eating protein bars regularly and dealing with bloating, gas, or stomach issues, flip the bar over and read the label. There's a very good chance sugar alcohols are behind it.

The fix is straightforward. Choose bars sweetened with monk fruit or stevia instead of maltitol, sorbitol, or erythritol. Your gut will thank you within a few days.

And if you want to try a bar that was built specifically around this principle from day one, The Volk Bar has zero sugar alcohols, monk fruit sweetening, and prebiotics for gut health. Don't take our word for it. Read the label. That's all we ask.