Oxalates (oxalic acid) are plant compounds that bind calcium and other minerals. For most people they are harmless, but recurrent calcium-oxalate kidney-stone formers are advised to moderate the highest sources.
What is Oxalates?
Oxalates is a plant organic acid that plays a critical role in binding dietary calcium into insoluble crystals. While many general diets overlook it, maintaining optimal levels of Oxalates is frequently tracked by people working to optimize their Urinary oxalate.
Top Foods High in Oxalates
A data-driven breakdown of the foods with the highest concentration of Oxalates per 100 g.
| Food | Oxalates |
|---|---|
| Spinach | 970 mg |
| Dark Chocolate (70–85%) | 700 mg |
| Almonds | 469 mg |
| Tofu | 280 mg |
| Sweet Potato | 240 mg |
| Chia Seeds | 200 mg |
| Beetroot | 152 mg |
| Buckwheat | 130 mg |
How Oxalates Impacts Urinary oxalate
Research links diets rich in Oxalates to changes in Urinary oxalate. Optimizing intake of these foods can support healthy Urinary oxalate levels via adding to the calcium-oxalate load the kidneys must clear.
How to Reduce Oxalates
Soluble oxalate leaches into cooking water, so wet-cooking methods cut it far more than dry heat.
| Method | Typical reduction | How it works |
|---|---|---|
| Boiling & draining | ~30–87% | Boil leafy greens and discard the water; soluble oxalate leaches out (steaming is much weaker). |
| Pairing with calcium | absorption ↓ | Dietary calcium binds oxalate in the gut so less reaches the kidneys. |
| Soaking (legumes/grains) | modest | Reduces a portion before cooking. |
Scientific references & clinical evidence
This guide is built on peer-reviewed research — verify the primary sources below.
Written by the Nutrition Encyclopedia team · medically reviewed by Dr. Sunaina Tariq, MBBS
Last updated 22 June 2026
How we source & verify data · Medical disclaimer
Nutrition values are approximations compiled from public food-composition databases (USDA FoodData Central) and are provided for educational purposes only — not medical advice.