onion
Vegetables
Is onion high in fructans?
Find out whether onion is high or low in fructans, see its exact rating, and check its FODMAP, salicylate, oxalate and diet compatibility all in one place.
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Sensitivity notes
Why fructans food checker matters
Fructans are chains of fructose molecules found in wheat, onions, garlic, and many other foods. They're a type of FODMAP that can cause digestive symptoms in sensitive individuals because they're not well absorbed in the small intestine.
- Garlic-infused oil is low-FODMAP since fructans don't dissolve in oil
- Green parts of leeks and scallions are lower in fructans
- Sourdough bread may be better tolerated than regular wheat bread
Triggers
Diets
Serving size, prep, and portion notes for onion
Onion is graded E for fructans and E for total FODMAPs, the top of our scale, which is why it is the single most common trigger people uncover once they start logging food against symptoms. The reaction is a carbohydrate problem rather than an allergy: onion is A for histamine, A for oxalates, A for lectins and A for nightshades, so if onion bloats you the fructans are almost certainly the mechanism. It also grades E for low fermentation SIBO plans. The frustrating part is that fructans are water soluble and heat stable, so caramelizing, slow simmering or fishing the pieces out of a sauce does not make onion any safer, and onion hidden in stock, gravy and spice blends is why so many people react to restaurant food they cannot account for.
Watch for
Fructans and total FODMAPs both graded E, the highest tier we use, and the grade does not soften between raw and cooked onion / Cooking is not a fix: fructans dissolve out of the onion into the pan and stay in the liquid, so straining the pieces out leaves the trigger in the sauce / Hidden onion drives most unexplained flare-ups: stock cubes, gravies, curry pastes, spice rubs, chips and anything listed as seasoning or natural flavor / Graded E for low fermentation SIBO, so onion is usually one of the first things pulled when working through a SIBO protocol / Clean on the rest of the chemistry (histamine A, oxalate A, lectin A, nightshade A, with only a borderline B for histamine liberation), which is why an onion reaction is nearly always intolerance rather than allergy
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Fructans Guide
Everything you need to know about fructans sensitivity and smart food choices.
Fructans are chains of fructose molecules found in wheat, onions, garlic, and many other foods. They're a type of FODMAP that can cause digestive symptoms in sensitive individuals because they're not well absorbed in the small intestine.
Sensitivity varies widely. What triggers one person may be fine for another. Track your reactions to find your personal threshold.
These foods are generally well-tolerated for Fructans sensitivity:
View all safe options
These foods have moderate levels and may be tolerated in small amounts:
These foods are high in fructans and may trigger symptoms:
View full list
If you're sensitive to Fructans, consider these strategies:
- 1Garlic-infused oil is low-FODMAP since fructans don't dissolve in oil
- 2Green parts of leeks and scallions are lower in fructans
- 3Sourdough bread may be better tolerated than regular wheat bread
- 4Spelt and ancient grains still contain fructans despite marketing claims
- 5Portion size matters - small amounts may be tolerable
Pro tip: Keep a food diary to track your reactions. The Triggerbites app makes this easy with automatic pattern detection.
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Get the AppFAQ
Is onion high in Fructans?
Fructans: higher signal - consider smaller servings or swaps.
Can I still eat onion if I'm sensitive to Fructans?
Best to avoid or test carefully with a small amount.
What else should I check?
Check FODMAPs, Low Fermentation, and FODMAPs next for a fuller picture.