How to cook spinach to avoid oxalates?

November 18, 2025 •

4 min read

According to research, boiling can reduce the soluble oxalate content in spinach by over 60%, making it a highly effective method for those concerned about their intake. This guide explores how to cook spinach to avoid oxalates and enjoy its nutritional benefits without the worry.

Quick Summary

The most effective method for reducing soluble oxalates in spinach is boiling, followed by draining the water. Combining cooked spinach with calcium-rich foods can further minimize absorption, helping individuals concerned about kidney stones manage their diet.

Key Points

Boiling is Most Effective: The best method to reduce soluble oxalates in spinach is boiling or blanching in a generous amount of water.
Drain and Discard Water: Always discard the cooking water after boiling, as it contains the majority of the leached oxalates.
Pair with Calcium: Combine your cooked spinach with calcium-rich foods like cheese or yogurt to bind any remaining oxalates and prevent absorption.
Rinse and Squeeze: After boiling, rinse the spinach under cold water and squeeze out any excess liquid to further reduce oxalate content.
Moderate Portions: For those with concerns, moderate portion sizes of cooked spinach to manage overall oxalate intake.
Consider Alternative Greens: Incorporate other leafy greens like kale or bok choy into your diet, which have naturally lower oxalate levels.

Understanding Oxalates in Spinach

Spinach is a nutrient-dense leafy green, but it contains high levels of oxalates, or oxalic acid, which can bind to minerals like calcium and hinder their absorption. For most people, this isn't a concern, but for individuals prone to kidney stones, managing oxalate intake is important. Cooking methods that cause the water-soluble oxalates to leach out are key to enjoying spinach with lower risk.

The Science Behind Oxalate Reduction

Oxalic acid in plants exists in both soluble and insoluble forms. While insoluble oxalates are less of a concern, soluble oxalates are readily absorbed by the body. The key to reducing your intake is using a cooking method that encourages these soluble compounds to migrate out of the plant tissue and into the cooking liquid. Higher temperatures and the use of water are the most effective drivers of this process. Discarding the cooking water is crucial, as that's where the majority of the leached oxalates reside.

Comparing Cooking Methods for Oxalate Reduction


Method	Effectiveness	Process	Key Considerations
Boiling	High (30-87% reduction)	Boil in ample water, drain thoroughly.	Can lead to a loss of water-soluble vitamins like Vitamin C and folate.
Blanching	High (similar to boiling)	Quick boil (1-3 minutes) followed by an ice bath.	Best for preserving color and texture. Drain and squeeze well.
Steaming	Moderate (less effective than boiling)	Steam in a basket over boiling water.	Oxalates can be released into the condensed steam. Less loss of nutrients.
Microwaving	Moderate (variable reduction)	Cook in a small amount of water.	Less effective as oxalates are not fully leached. Use minimal water to preserve nutrients.
Stir-frying	Low (not effective)	Cook quickly in a pan with oil.	Oxalates remain in the food as no water is used to leach them out.
Raw (uncooked)	None	Consumed fresh, such as in salads or smoothies.	Highest oxalate content; not recommended for those with sensitivities.

Practical Steps for Low-Oxalate Spinach

To effectively reduce oxalates, the process starts with proper preparation. Opt for boiling or blanching as your primary cooking method. If you choose to steam, understand that the reduction will be less significant.

Here’s a step-by-step guide for preparing low-oxalate spinach:

Rinse Thoroughly: Wash the spinach leaves under running water to remove any surface dirt and some initial oxalates. Consider chopping the spinach into smaller pieces, which further enhances the leaching process during boiling.
Boil in Ample Water: Bring a large pot of water to a rolling boil. Use a generous amount of water to ensure maximum leaching of oxalates. Add the spinach to the boiling water.
Cook for 2-3 Minutes: Boil for approximately 2 to 3 minutes, starting the timer once the water returns to a boil. Some studies have shown up to 72% reduction with this timing.
Strain and Drain: Promptly remove the spinach from the boiling water using a colander. For maximum oxalate removal, press or squeeze the spinach with the back of a spoon to remove any excess cooking liquid. Do not reuse this water, as it is now high in oxalates.
Rinse and Squeeze: Rinse the drained spinach under cold water to stop the cooking process and preserve its bright green color. Squeeze the spinach again to remove as much water as possible.

Enhancing Your Meal with Calcium

Pairing your low-oxalate spinach with a calcium-rich food can act as a secondary defense. The consumed calcium will bind with any remaining oxalates in your digestive tract, forming insoluble compounds that are excreted from the body.

Add Dairy: Stir some parmesan or ricotta cheese into your cooked spinach.
Use Yogurt: Serve a dollop of yogurt on the side, or incorporate it into a sauce.
Incorporate Calcium-Rich Seeds: Sprinkle sesame seeds or add a spoonful of tahini for a nutty flavor and calcium boost.

Beyond Cooking: Other Factors for Lowering Oxalates

Cooking is a major factor, but other elements can also influence your overall oxalate intake. Consider these practices for a more comprehensive strategy.

Portion Control: Even with proper cooking, spinach remains a medium-oxalate food. Moderating your portion size helps control overall intake.
Stay Hydrated: Drinking plenty of water helps flush the kidneys and prevent mineral crystallization.
Choose a Variety of Greens: Don't rely solely on spinach for your leafy greens. Incorporate lower-oxalate alternatives like kale, bok choy, or cabbage into your diet.

Conclusion

By adopting simple techniques like boiling or blanching, you can significantly reduce the oxalate content in spinach, making it a safer and more enjoyable food for those sensitive to these compounds. Remember to discard the cooking liquid and pair your spinach with calcium-rich foods for added protection. These methods allow you to continue benefiting from the iron and vitamins in this superfood while actively managing your health concerns related to oxalates. Consulting a healthcare provider or a registered dietitian is always recommended if you have specific health concerns, such as a history of kidney stones.

Frequently Asked Questions

Steaming is less effective than boiling for removing oxalates because the compounds are not leached into a large volume of water. While some reduction occurs, boiling provides a more significant decrease in soluble oxalates.

Raw spinach contains the highest concentration of oxalates. Individuals on a low-oxalate diet should avoid or significantly limit their consumption of raw spinach and instead opt for properly cooked versions.

Soluble oxalates are water-soluble compounds that can be absorbed by the body, posing a higher risk for stone formation. Insoluble oxalates are less of a concern because they are less bioavailable and pass through the digestive system more easily.

Boiling for 2-3 minutes is sufficient to achieve a significant reduction in soluble oxalates. The key is to use a high volume of water and ensure it returns to a boil after adding the spinach.

Yes, pairing spinach with calcium-rich foods like milk or cheese can help. The calcium binds with oxalates in the digestive tract, preventing them from being absorbed into the bloodstream.

Yes, while boiling effectively removes oxalates, it can also lead to a loss of some water-soluble vitamins, such as Vitamin C and some B vitamins. The trade-off is often considered worthwhile for those managing oxalate intake.

Using a smaller amount of water reduces the efficiency of oxalate removal. For maximum leaching, it is important to boil spinach in a generous amount of water and then discard that liquid.