onion
Vegetables
Is onion high in oxalates?
Is onion high or low in oxalates? See its exact rating, how much counts as a portion, and its FODMAP, salicylate, oxalate and diet compatibility in one place.
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Sensitivity notes
Why oxalates food checker matters
Oxalates are compounds found in many plant foods that can bind with calcium to form crystals. High oxalate intake may contribute to kidney stones in susceptible individuals and can cause other symptoms in those with oxalate sensitivity.
- Stay well-hydrated to help prevent oxalate crystal formation
- Pair high-oxalate foods with calcium-rich foods to bind oxalates
- Cooking and boiling can reduce oxalate content in some foods
- Spread oxalate intake throughout the day rather than one large dose
- Consider probiotics - some gut bacteria break down oxalates
Sensitivities
What onion contains
FODMAPs
Histamine & Amines
Plant compounds
Irritants
Additives
Allergens
Diet fit
Where onion fits
Therapeutic diets
Lifestyle diets
Religious diets
What to know about 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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Oxalates Guide
Everything you need to know about oxalates sensitivity and smart food choices.
Oxalates are compounds found in many plant foods that can bind with calcium to form crystals. High oxalate intake may contribute to kidney stones in susceptible individuals and can cause other symptoms in those with oxalate sensitivity.
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 Oxalates sensitivity:
View all safe options
These foods have moderate levels and may be tolerated in small amounts:
These foods are high in oxalates and may trigger symptoms:
View full list
If you're sensitive to Oxalates, consider these strategies:
- 1Stay well-hydrated to help prevent oxalate crystal formation
- 2Pair high-oxalate foods with calcium-rich foods to bind oxalates
- 3Cooking and boiling can reduce oxalate content in some foods
- 4Spread oxalate intake throughout the day rather than one large dose
- 5Consider probiotics - some gut bacteria break down oxalates
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 Oxalates?
Oxalates: low signal for most people.
Can I still eat onion if I'm sensitive to Oxalates?
Usually fine in normal portions.
What else should I check?
Check FODMAPs, Fructans, and Low Fermentation next for a fuller picture.