Are greens high in oxalates?

October 31, 2025 •

2 min read

A single cup of raw spinach contains over 650mg of oxalates, demonstrating that the quantity can vary dramatically among greens. For individuals sensitive to these compounds, this begs the question: are greens high in oxalates and should they be managed in your diet?.

Quick Summary

The oxalate content in greens varies significantly, with some like spinach and Swiss chard being very high, while many others such as kale and bok choy are surprisingly low in this compound.

Key Points

Not All Greens Are High in Oxalates: While popular greens like spinach and Swiss chard contain high oxalate levels, many other leafy vegetables such as kale, bok choy, and arugula are surprisingly low in this compound.
Kidney Stone Risk: High oxalate intake can contribute to the formation of calcium oxalate kidney stones, particularly in susceptible individuals.
Cooking Reduces Oxalates: Boiling and steaming greens can significantly reduce their oxalate content, with boiling being the most effective method, especially when the cooking water is discarded.
Pairing with Calcium is Key: Eating calcium-rich foods with high-oxalate greens helps the calcium and oxalate bind in the gut, which minimizes the absorption of oxalates by the body.
Spinach is an Outlier: When it comes to oxalate content, spinach is a major outlier, containing exceptionally high amounts compared to most other greens.
Bioavailability Matters: The calcium in low-oxalate greens is more bioavailable than the calcium in high-oxalate greens like spinach, where it is bound and not easily absorbed.

What Are Oxalates?

Oxalates, or oxalic acid, are natural compounds in plants. They can bind with minerals like calcium in the digestive system, potentially hindering absorption and contributing to calcium oxalate kidney stone formation. While generally safe, high intake can be a concern for those prone to kidney stones or with certain gut conditions.

The Health Implications of Oxalate Intake

Most people can consume high-oxalate foods in moderation as the body excretes excess. Those at higher risk may need a low-oxalate diet.

Kidney Stones: Oxalate binding with calcium forms crystals in the kidneys, leading to stone formation.
Mineral Absorption: Oxalate can reduce the absorption of calcium and magnesium.
Other Factors: Fat malabsorption and high vitamin C intake can increase oxalate issues.

Not All Greens Are Created Equal

The oxalate content of leafy greens varies widely. Some have high levels, while others are low-oxalate options.

High-Oxalate Greens to Consider Limiting

Spinach: Known for high oxalate content, with raw spinach containing hundreds of milligrams per cup.
Swiss Chard: Another green with very high oxalate levels.
Beet Greens: High in oxalates.
Parsley: Has significant oxalate content.

Low-Oxalate Greens for Safe Consumption

Consider these low-oxalate options:

Kale: Surprisingly low in oxalates, with about 2mg per raw cup.
Bok Choy: Very low oxalate content.
Arugula: Low in oxalates.
Cabbage: All types are low in oxalates.
Collard Greens: Lower in oxalates than spinach.
Mustard and Turnip Greens: Also low in oxalates.
Lettuce (Romaine, Iceberg): Very low in oxalates.

How to Reduce Oxalates in Greens

Cooking can help reduce oxalates as they are water-soluble.

Boiling: Most effective, as oxalates leach into the water. Boiling spinach can reduce oxalates by over half.
Steaming: Less effective than boiling but still helps reduce levels.
Combining with Calcium: Eating high-oxalate foods with calcium-rich foods can help bind oxalates in the gut, reducing absorption.

Comparison of Oxalate Levels in Popular Greens


Green	Raw Oxalate (per 1 cup)	Cooked Oxalate (per ½ cup)	Oxalate Level	Calcium Absorption
Spinach	~656 mg	~755 mg	Very High	Poor (Oxalates bind calcium)
Swiss Chard	~350 mg	Not specified	Very High	Poor (Oxalates bind calcium)
Kale	~2 mg	Not specified	Low	Good (Low oxalate)
Bok Choy	~1 mg	Not specified	Low	Good (Low oxalate)
Collard Greens	Not specified	~10 mg	Low	Good (Low oxalate)
Arugula	~0 mg	Not specified	Low	Good (Low oxalate)

*Note: Cooked values can appear higher due to concentration, but cooking generally reduces total oxalate content, especially with draining.

Conclusion: Balancing Greens and Oxalate Intake

In summary, while some greens are high in oxalates, many are not. Understanding the variation and managing intake based on health needs is key. For most, the benefits of greens outweigh the risks with moderate consumption. Those with kidney stone history should favor low-oxalate varieties and use preparation methods to reduce oxalate content in high-oxalate greens. Diversifying your greens intake and proper preparation allows you to enjoy their benefits while managing oxalate levels.

For further dietary guidance, consult resources from trusted institutions like the National Kidney Foundation, especially if managing a specific health condition.

Frequently Asked Questions

The greens highest in oxalates include spinach, Swiss chard, and beet greens. A single cup of raw spinach has an extremely high oxalate content compared to other leafy vegetables.

Excellent low-oxalate greens include kale, bok choy, cabbage, romaine lettuce, collard greens, and arugula.

Yes, cooking can reduce the oxalate content of greens. Boiling is the most effective method, as oxalates are water-soluble and will leach into the cooking water. Steaming is also effective to a lesser degree.

No, individuals with a history of kidney stones do not need to avoid all greens. They should focus on limiting or preparing high-oxalate greens like spinach while favoring low-oxalate varieties like kale and bok choy.

Eating calcium-rich foods alongside high-oxalate greens can help reduce oxalate absorption. The calcium binds to the oxalates in the gut, forming insoluble compounds that are excreted from the body.

For most people, it is difficult to consume enough greens to cause a problematic oxalate overload. However, excessive consumption of high-oxalate greens, especially when juiced or blended, can pose a risk for some individuals.

The bioavailability of calcium is higher in low-oxalate greens like kale and bok choy. In high-oxalate greens like spinach, the oxalates bind to the calcium, making it less available for absorption by the body.