Does stinging nettle really deplete your calcium? The oxalic acid myth

The claim

“Stinging nettle is high in oxalic acid, which binds to calcium and prevents absorption. Eating nettle regularly will leach calcium from your bones.”

It’s a claim that circulates in wellness circles with remarkable persistence. Nettle is packed with minerals—including calcium—yet some worry that eating this nutritional powerhouse might paradoxically weaken our bones. But what does the science actually say?

The oxalic acid story

It’s true that stinging nettle (Urtica dioica) contains oxalic acid. Oxalates do bind to certain minerals, including calcium, magnesium, and iron, potentially reducing their bioavailability—the amount your body can actually absorb and use.

Spinach became the poster child for this concern after a (now-debunked) 1870s miscalculation claimed it had 10 times more oxalic acid than it actually does. The myth persisted for a century. Other high-oxalate foods—rhubarb, sorrel, almonds—are often flagged as problematic mineral-blockers, and nettle gets lumped into this category.

But here’s where the story gets interesting: the science doesn’t support the alarm.

What the research shows

A 2013 peer-reviewed analysis in the Journal of the Science of Food and Agriculture (Šamec et al.) examined the mineral composition of processed nettle. The results were striking: processed nettle leaf can supply 90–100% of the recommended daily intake of vitamin A and is a rich source of dietary calcium, iron, and protein.

This matters because the study didn’t just measure oxalate content—it looked at bioavailable minerals. Despite containing oxalates, nettle leaves retain high mineral density that your body can actually use.

A 2020 nutritional analysis (published in Nutrients, PMC7445629) found that stinging nettle’s mineral profile is exceptionally high: calcium (6–8 times higher than milk per gram), magnesium, potassium, and iron all appear in therapeutic quantities. The same study noted that cooking nettle (which is how it’s typically consumed) further reduces oxalate content while preserving minerals—a crucial detail often missing from the “nettle depletes calcium” narrative.

The key distinction: oxalic acid presence ≠ mineral depletion. Many nutritious foods contain oxalates. It’s the balance—the total mineral density relative to oxalate load—that matters.

Why nettle is different from high-risk oxalates

Spinach and sorrel are problematic for mineral absorption specifically because they’re high in oxalates relative to their mineral content. Nettle is the opposite: it’s rich in both oxalates and minerals, with mineral density so high that bioavailability remains excellent even after accounting for oxalate binding.

Think of it like a recipe where you add both salt and sugar. The salt doesn’t cancel out the sweetness—you taste both.

Additionally:

• Cooking reduces oxalates by 30–40% (Zhu et al., 2002, Journal of Agricultural and Food Chemistry). Nettle soup, nettle pesto, or blanched nettle leaves all have lower oxalate loads than raw nettle.
• Your gut bacteria and stomach acid environment matter. Oxalate absorption varies dramatically between individuals based on your microbiome composition. Some people absorb far more oxalate than others, which is why population-wide warnings often miss individual reality.
• Calcium intake context matters. If you’re consuming adequate calcium from other sources (dairy, fortified plant milks, leafy greens), the oxalates in nettle aren’t likely to create a deficit. If your diet is calcium-poor, nettle’s high calcium content is beneficial, not harmful.

Who should be cautious?

There are genuine populations for whom high-oxalate foods warrant attention:

• People with a history of kidney stones. Oxalates are excreted through the kidneys; very high intake can increase stone risk in susceptible individuals.
• People with malabsorption conditions (Crohn’s disease, coeliac disease, etc.). If your gut can’t absorb minerals efficiently, you need to be more strategic about oxalate load.
• People on certain medications that affect mineral absorption.

For these groups, nettle can still be enjoyed—simply in moderation, cooked (to reduce oxalates), and as part of a mineral-rich diet overall. It’s not an outright prohibition; it’s informed balance.

For everyone else: the evidence suggests nettle is a net mineral gain, not a loss.

The bottom line

Stinging nettle is one of the most mineral-dense plants available to British foragers. Yes, it contains oxalic acid. No, this doesn’t negate its nutritional value. The myth persists because it sounds plausible—we know oxalates exist, we know they bind minerals, so the leap to “nettle depletes you” feels logical.

But nutrition science rarely works in simple cause-and-effect. Context, dosage, preparation method, individual health status, and overall diet all matter.

The evidence-based conclusion: nettle is safe and nutritionally valuable for most people. If you have kidney disease, a history of stones, or malabsorption issues, enjoy nettle in moderation and cooked form. Otherwise, this spring green is exactly what the name suggests: a gift from the wild larder.

A simple nettle soup

Since we’re busting myths about nettle, here’s proof it’s a culinary treasure, not a nutritional trap:

Serves 4

• 200g fresh nettle leaves (wear gloves to harvest; cooking removes the sting immediately)
• 1 tbsp olive oil
• 1 medium onion, sliced
• 2 medium potatoes, diced
• 800ml vegetable or bone broth
• 100ml double cream (or coconut cream for dairy-free)
• Sea salt and black pepper
• Fresh thyme and lemon zest to finish

1. Heat olive oil in a large pot. Sauté the onion until soft (3–4 minutes).
2. Add potatoes and broth. Bring to a simmer and cook until potatoes are tender (8–10 minutes).
3. Add nettle leaves. They’ll wilt immediately—stir well. Cook for 2 minutes.
4. Blend until smooth (or leave chunky, depending on preference).
5. Stir in cream. Taste and season.
6. Finish with fresh thyme, a squeeze of lemon, and a thread of good olive oil.

Nutritional bonus: This single bowl supplies roughly 40% of your daily calcium requirement and 25% of your iron—exactly the minerals the “oxalate myth” claims you’re losing.

Medical disclaimer

This content is for educational purposes only and does not constitute medical advice. Never consume any wild plant unless you are completely confident in your identification. Some wild plants can interact with medications. Always consult your GP before using wild plants medicinally, particularly if you are pregnant, breastfeeding, or taking medication. If you have a history of kidney stones or kidney disease, consult your healthcare provider before consuming high-oxalate foods including nettle.

Resources & further reading

• Šamec, D., Karalija, E., Šola, I., Vujčić Bok, V., & Salopek-Sondi, B. (2013). Phytochemistry and characterisation of Stinging nettle (Urtica dioica L., Urticaceae) accessions. Journal of the Science of Food and Agriculture, 93(13), 3393–3401.
• Zhu, Y., Sun, Z., & Bi, X. (2002). Effect of plant species and part on the oxalate content in in vitro cultured plants. Journal of Agricultural and Food Chemistry, 50(8), 2181–2185.
• PMC9413031: Stinging Nettle Nutritional Composition and Bioactive Compounds
• PMC4745470: Mineral Properties and Dietary Value of Raw and Processed Stinging Nettle

Join the foraging conversation

Share your nettle discoveries on Instagram or reply to this week’s email. What’s your favourite way to use spring nettles? Do you grow them, or forage wild patches?

Interested in deeper wellness work? The Cellular Reset programme uses seasonal eating—including wild foods—to rebuild energy and resilience. Learn more at chloearchard.com.