Understanding Oxalates: What They Are and How They Affect Your Body
Oxalates (also known as oxalic acid or oxalic salts) are naturally occurring compounds found in many plant foods. They’re sometimes called “anti-nutrients” because they can bind to minerals such as calcium and magnesium, making these minerals harder for your body to absorb.
Our own bodies also produce oxalate as part of normal metabolism (for example, when breaking down vitamin C), so diet is only one piece of the puzzle.
How Oxalates Can Affect the Body
1. Kidney Stones
Oxalates can bind to calcium in the urine, forming calcium oxalate crystals — the most common type of kidney stone. People prone to stones or with certain gut issues may need to keep an eye on their intake.
2. Reduced Mineral Absorption
High-oxalate foods can slightly reduce calcium absorption when eaten in large amounts, though in a balanced diet this effect is usually minor.
3. Gut and Microbiome Factors
Healthy gut bacteria (especially Oxalobacter formigenes) help break down oxalate before it’s absorbed. Those who’ve had antibiotics or digestive conditions may absorb more oxalate than usual.
Foods High in Oxalates
Some plant foods are naturally rich in oxalates. Here are a few of the main ones:
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Spinach and Swiss chard
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Beetroot and beet greens
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Rhubarb
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Nuts and nut butters (especially almonds and cashews)
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Soy products (tofu, soy milk)
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Beans and lentils
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Cocoa, dark chocolate
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Black tea
Cooking methods such as boiling and discarding the water can reduce oxalate content in vegetables.
Keeping Balance
Oxalates aren’t all bad — they’re part of many healthy foods. The key is moderation and balance.
Tips:
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Pair oxalate-rich foods with calcium (e.g. cheese, yoghurt) to bind oxalate in the gut.
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Stay hydrated to dilute urine and reduce the risk of kidney stone formation.
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Vary your greens — swap spinach for kale, romaine or rocket now and then.
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Support gut health with fibre and fermented foods.
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If you’ve had kidney stones, check with your GP or dietitian for tailored advice.
Key Takeaways
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Oxalates are natural plant compounds that can affect mineral absorption.
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High intakes may raise the risk of kidney stones for some people.
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Cooking and food pairing can reduce oxalate absorption.
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For most people, a balanced diet with plenty of variety poses no concern.