Does Cooking Kale Reduce Oxalates? A Deep Dive into Nutrient Absorption

December 21, 2025 •

3 min read

According to a study published in the Italian Journal of Food Science, cooking methods like boiling and air frying significantly decreased the oxalate content in kale. So, does cooking kale reduce oxalates? The answer is yes, certain cooking methods are highly effective at lowering this compound.

Quick Summary

Cooking methods, especially boiling and blanching, can effectively reduce the oxalate levels found in kale. The water-soluble nature of oxalates allows them to leach out during cooking, which can enhance mineral absorption and potentially benefit kidney health for sensitive individuals.

Key Points

Boiling is Most Effective: Boiling or blanching kale and discarding the water is the best way to significantly reduce soluble oxalate content.
Steaming is Moderately Effective: Steaming can also reduce oxalates, but it is less potent than boiling, though it preserves more water-soluble vitamins.
Kale is Lower in Oxalates than Spinach: Kale naturally has a lower oxalate content compared to other leafy greens like spinach and Swiss chard, making it a safer choice for many.
Pair with Calcium: Eating kale with calcium-rich foods helps the mineral bind with oxalates in the gut, preventing their absorption.
Discard the Cooking Water: To ensure oxalate removal, always discard the water used for boiling or blanching, as the soluble oxalates leach into it.
High-Heat Cooking is Ineffective: Sautéing, roasting, and air frying do not remove oxalates effectively because they don't involve leaching into water.
Hydration is Crucial: Maintaining adequate hydration is important for diluting oxalates in the body and reducing the risk of kidney stone formation.

What are Oxalates and Why Should You Care?

Oxalates, or oxalic acid, are naturally occurring compounds found in many plants, including fruits, vegetables, nuts, and grains. As an 'antinutrient,' oxalates can bind to essential minerals like calcium, magnesium, and iron in the digestive system, preventing your body from absorbing them. The most significant concern surrounding high oxalate intake is the formation of calcium oxalate crystals, which are responsible for up to 80% of all kidney stones. While most people can consume moderate amounts of oxalates without issue, individuals prone to kidney stones or with other related health concerns may need to reduce their intake.

Soluble vs. Insoluble Oxalates

Oxalates come in two forms: soluble and insoluble. Soluble oxalates are bound to minerals like sodium and potassium and easily dissolve in water. Insoluble oxalates are bound to calcium and form crystals that are not water-soluble. This distinction is important because cooking primarily affects the soluble form.

Does Cooking Kale Reduce Oxalates?

Yes, cooking kale can significantly reduce its oxalate content. This is because water-soluble oxalates leach out into the cooking water. Discarding the cooking water is crucial for reducing oxalate levels.

The Best Cooking Methods for Reducing Oxalates

Boiling and Blanching: These are the most effective methods. Boiling can remove a significant portion of oxalates, with some studies showing reductions over 60%. Blanching is also highly effective.
Steaming: Less effective than boiling, steaming still reduces oxalates. It retains more water-soluble vitamins compared to boiling.

Less Effective Cooking Methods

Sautéing, Roasting, and Air Frying: These methods are not effective for reducing oxalates as they don't involve water. While air frying might show some decrease, it's not as reliable as boiling.

Comparison of Cooking Methods for Oxalate Reduction


Cooking Method	Effectiveness at Reducing Oxalates	Effect on Water-Soluble Nutrients	Best For...
Boiling/Blanching	High	Significant nutrient loss	Maximum oxalate reduction
Steaming	Moderate	Less nutrient loss	Balancing nutrient retention and oxalate reduction
Sautéing/Roasting	Low	Retains fat-soluble vitamins	Flavor and texture (not for oxalate reduction)
Microwaving	Low to Moderate	Generally retains nutrients well	Quick cooking; less effective for leaching oxalates

Practical Tips for Managing Oxalate Intake

To manage oxalate intake, especially if you are prone to kidney stones:

Pair with Calcium: Combine kale with calcium-rich foods to bind oxalates in the gut.
Stay Hydrated: Drinking water helps dilute oxalates in urine.
Rotate Greens: Vary high-oxalate greens like spinach with lower-oxalate options like bok choy.
Consult a Professional: If you have kidney stone history, talk to a doctor or dietitian.

The Low-Oxalate Perspective: Is Raw Kale a Concern?

Kale is relatively low in oxalates compared to spinach. For most healthy people, raw kale is not a concern. Issues may arise with high consumption or for those with conditions affecting oxalate metabolism. Blended raw kale can lead to more rapid oxalate absorption in sensitive individuals. Cooking is the most reliable way to reduce potential risk.

Conclusion

Kale is a healthy food, and for most people, oxalates are not a significant concern. If you need to reduce oxalate intake, boiling or blanching and discarding the water is the most effective method. Combining cooked kale with calcium-rich foods and staying hydrated provides extra protection. A balanced diet with various raw and cooked vegetables is generally recommended.

Optimize Your Kale Intake

To maximize the benefits of kale while minimizing oxalate concerns:

Steam kale to preserve vitamins while reducing oxalates.
Always eat cooked kale with a calcium source.
Alternate raw kale with other leafy greens.
Chop kale before boiling for better oxalate leaching.
Seek medical advice for kidney health concerns.

Outbound Link

For further information on oxalates and kidney stone prevention, the National Kidney Foundation provides excellent resources on diet management.

Frequently Asked Questions

Boiling or blanching kale is the most effective method for removing oxalates, as the water-soluble oxalates leach out into the cooking water, which is then discarded.

For most healthy individuals, eating raw kale is perfectly safe. The concern about oxalates is primarily for those with a history of kidney stones or other related health issues.

No, steaming is less effective than boiling at reducing oxalates. While some leaching occurs, boiling provides more direct water contact for the oxalates to dissolve into.

Roasting is not an effective method for reducing oxalates. The high-heat, dry cooking process does not allow the water-soluble oxalates to leach out.

While boiling is best for reducing oxalates, it can also lead to a loss of water-soluble vitamins. Steaming retains more nutrients while still providing a moderate reduction in oxalates.

If you are very sensitive to oxalates, it is generally safer to consume cooked kale. Blending raw kale can make oxalates more readily absorbed in some individuals.

To lower oxalate intake, boil or blanch kale and discard the cooking water. You can also combine it with calcium-rich foods like dairy or calcium-set tofu.

No, kale has a relatively low oxalate content compared to other popular greens like spinach and Swiss chard. This makes it a better choice for those on a low-oxalate diet.