Sugar alcohols are carbohydrates with sweetness properties but incomplete digestibility, resulting in lower caloric content than sugar. Understanding their metabolism, digestive effects, and individual properties explains why they cause bloating, why benefits vary by compound, and practical consumption limits.
What Are Sugar Alcohols
Sugar alcohols are carbohydrates structurally similar to both sugars and alcohols, but metabolized differently than either. They’re neither “sugar” nor “alcohol”—the names are misleading. Common examples: sorbitol, xylitol, mannitol, erythritol. They taste sweet but are only partially digestible, resulting in lower caloric content than equivalent sugars.
The partial digestibility is intentional—the molecules are designed to be sweet but not fully metabolized, creating sweetness without equivalent calories.
Common Sugar Alcohol Types
Sorbitol: 50-60% as sweet as sugar, approximately 2.6 cal/g (sugar is 4). Well-absorbed but causes significant gas/bloating. Xylitol: 100% as sweet as sugar, approximately 2.4 cal/g. Better tolerated than sorbitol but still causes digestive issues. Mannitol: 50-70% as sweet as sugar, approximately 1.6 cal/g. Poor absorption, significant digestive side effects. Erythritol: 70-80% as sweet as sugar, approximately 0.2 cal/g (essentially zero calories). Approximately 90% absorbed and rapidly excreted, fewer digestive issues.
Erythritol is the superior sugar alcohol from digestive perspective—nearly zero calories and minimal bloating. Xylitol offers better sweetness but more digestive side effects. Sorbitol and mannitol are problematic for most consumers.
Digestive & Metabolic Fate
Sugar alcohols are absorbed in the small intestine but not metabolized efficiently: (1) Partial absorption—approximately 50-90% absorption depending on type. (2) Unabsorbed portion passes to the colon. (3) Colonic bacteria ferment unabsorbed sugar alcohols. (4) Fermentation produces gases (hydrogen, methane, CO₂) and short-chain fatty acids. (5) Gas accumulation causes bloating, cramping, flatulence.
The digestive side effects result directly from bacterial fermentation—the same mechanism fiber causes bloating. Sugar alcohols are essentially partially-fermented carbohydrates.
Why They Cause Bloating
The amount of gas depends on: (1) Absorption rate: Erythritol is nearly completely absorbed (minimal colon content, minimal gas). Sorbitol is poorly absorbed (substantial colon content, maximum gas). (2) Quantity consumed: Large amounts overwhelm absorption capacity, increasing colon content. (3) Individual tolerance: Varies by gut microbiota composition—different bacterial populations produce different gas amounts. (4) Adaptation: Repeated consumption may reduce symptoms as microbiota adapts.
Practically: erythritol at moderate doses (10-20g) causes minimal bloating. Sorbitol at equivalent sweetness doses causes substantial bloating. Individual tolerance varies widely.
Calories & Sweetness Comparison
Sugar: 4 cal/g, 1.0 sweetness. Sorbitol: 2.6 cal/g, 0.6 sweetness (need 1.67x weight for equivalent sweetness = 4.3 cal/equivalent sweetness, WORSE than sugar). Xylitol: 2.4 cal/g, 1.0 sweetness. Erythritol: 0.2 cal/g, 0.75 sweetness (need 1.33x weight = 0.27 cal/equivalent sweetness, MUCH BETTER than sugar).
Erythritol is the only sugar alcohol offering clear caloric advantage over sugar on an equivalent-sweetness basis. Others don’t meaningfully reduce calories when adjusted for sweetness.
Health Effects & Claims
Advantages: (1) Lower glycemic response than sugar (some sugar alcohols). (2) Don’t promote dental cavities (bacteria can’t ferment them efficiently for acid production). (3) Lower caloric content (particularly erythritol). Disadvantages: (1) Digestive side effects (bloating, gas). (2) Potential laxative effects at high doses. (3) Individual variation in tolerance (some people are very sensitive).
Sugar alcohols are reasonably safe but aren’t “free foods”—they have metabolic effects and digestive consequences. The health advantage over sugar is modest except for erythritol specifically.
Practical Consumption & Limits
Erythritol: Generally well-tolerated at 10-30g/day. Some sensitivity at higher doses. Xylitol: Comfortable for most at 5-15g/day. Higher doses often cause noticeable symptoms. Sorbitol/Mannitol: Problematic for most at >10g/day. Often used in medicinal products as intentional laxatives.
Practical guidance: start with small amounts, assess personal tolerance, avoid consuming large quantities. Sugar alcohols are acceptable for occasional use but aren’t unlimited-consumption sweeteners. Erythritol is superior for regular use due to minimal digestive effects.