Quick answer
Sugar alcohols (polyols) are a class of FODMAP carbohydrate. They pull water into the intestinal lumen osmotically and get fermented by gut bacteria — both mechanisms produce gas and bloating. The tolerance ranking from best to worst is generally: erythritol (well absorbed) → xylitol (moderate) → sorbitol and maltitol (high fermentation, worst for IBS). Choosing sweeteners for a low-FODMAP diet means knowing which polyols are in your protein bars, "sugar-free" candy, and keto desserts — most are maltitol or sorbitol.
This cluster is the hub. The full guide covers the mechanism, the per-sweetener ranking, and the alternatives that actually work.
What counts as a sugar alcohol
Sugar alcohols (polyols) are carbohydrates that look chemically like sugar but have an alcohol group. The common ones in food:
- Sorbitol (E420) — the original sugar alcohol, in apples, pears, prunes; widely used in "sugar-free" products.
- Mannitol (E421) — in mushrooms, cauliflower; used in some medical foods.
- Xylitol (E967) — in birch and beechwood; common in chewing gum and dental products.
- Maltitol (E965) — in "sugar-free" candy, protein bars, ice cream.
- Isomalt (E953) — in hard candies and chocolates.
- Lactitol (E966) — in baked goods.
- Erythritol (E968) — in "natural" sweeteners, monk-fruit blends, keto products.
- Polydextrose — a synthetic polymer of glucose; counts as a polyol.
They're often added to "sugar-free," "keto," "diabetic-friendly," and "low-carb" products.
Why they cause symptoms
Two mechanisms hit simultaneously:
- Osmotic effect — sugar alcohols don't get fully absorbed in the small intestine. The unabsorbed molecules pull water into the lumen. That distension is what produces cramps and, sometimes, diarrhea.
- Bacterial fermentation — once the unabsorbed polyols reach the colon, gut bacteria ferment them into gas (hydrogen, methane, CO2). That produces distension, bloating, and flatulence.
For people with IBS or visceral hypersensitivity, the same dose produces stronger symptoms at lower thresholds than for healthy controls.
The tolerance ranking
In general order from best to worst tolerated:
- Erythritol — about 60-90% absorbed in the small intestine, mostly excreted unchanged in urine. Very little fermentation. Best choice for sensitive guts, though high doses (>50g) still cause some symptoms.
- Xylitol — about 50% absorbed. Moderate fermentation. Common in chewing gum; doses above 30-50g cause symptoms.
- Sorbitol — about 50% absorbed. Heavily fermented. Worst for IBS. Hidden in "sugar-free" candy and many diet products.
- Maltitol — about 40% absorbed. Heavily fermented. The worst offender in "sugar-free" protein bars and chocolate.
- Isomalt, lactitol, mannitol — similar fermentation profile. All can cause symptoms at moderate doses.
The differences are large enough that switching from a maltitol-sweetened bar to an erythritol-sweetened one often resolves the worst symptoms.
What "low-FODMAP" actually means for sweeteners
The Monash FODMAP diet, the gold-standard low-FODMAP framework, classifies polyols by dose threshold:
- Erythritol: generally safe at typical use; limit at very high doses.
- Xylitol: limit to 15-30g per sitting.
- Sorbitol, mannitol: limit to 5-10g per sitting.
- Maltitol: limit strictly; even small doses cause symptoms in many IBS patients.
"Sugar-free" doesn't mean "low-FODMAP." A sugar-free chocolate sweetened with maltitol can be worse than the sugared version for someone with IBS.
Where they hide
Read labels on:
- Protein bars (maltitol is the most common sweetener).
- "Sugar-free" candy and chocolate (maltitol, sorbitol, isomalt).
- Keto ice cream (often maltitol or erythritol).
- Chewing gum and mints (xylitol, sorbitol).
- "Diabetic" cookies and baked goods (often maltitol, isomalt).
- Low-carb protein powder (check the sweetener carrier).
The cluster article on hidden polyols in packaged foods has a checklist.
Cluster contents
This guide is the hub. The full cluster covers:
- Sugar Alcohols and Gut Symptoms: What the Evidence Says — the original article that anchors this cluster.
- Erythritol vs Xylitol: Gut Tolerance Compared — head-to-head comparison, plus why some people react to erythritol and what to try instead.
- Low-FODMAP Sweetener Alternatives That Actually Work — the safe sweetener toolkit: stevia, monk fruit, glucose, sucrose, maple syrup at the right doses.
- Sorbitol and Maltitol: The Hidden Polyols in Packaged Foods — the label-reading checklist to spot them before you buy.
FAQ
Q: Are sugar alcohols safe? A: Yes, at typical doses. They're approved food additives worldwide. The issue is dose and individual sensitivity — not toxicity.
Q: Can sugar alcohols cause long-term gut damage? A: No. The effects are acute — bloating, gas, diarrhea. There's no evidence of damage to the gut lining from polyols.
Q: I'm on a low-FODMAP diet. Can I use any sweetener? A: Yes — table sugar (sucrose), glucose, maple syrup (in small amounts), and most stevia/monk-fruit products are fine. Avoid polyols at high doses.
Q: Why does erythritol sometimes bother me? A: Even erythritol can cause symptoms at very high doses (>50g), and a small percentage of people don't absorb it well. Switching to stevia or monk fruit solves it.
Q: How long does it take for symptoms to clear after I stop? A: Usually within 24-48 hours once the polyols clear the gut.
This article is for educational purposes only and isn't medical advice. If you have severe or persistent symptoms, work with a qualified clinician.