Do oxalates in spinach increase the risk of kidney stones?

Okay, let's talk about spinach and kidney stones, a topic many people are concerned about.

Will the Oxalate in Spinach Actually Cause Kidney Stones? – Don't Panic, It Depends!

Straight to the point:

For the vast majority of healthy people, eating spinach normally is generally not a concern for developing kidney stones because of it. However, if you already have kidney stones (especially calcium oxalate stones) or your doctor has identified you as prone to them, then you do need to be particularly careful.

Below, I'll break it down for you—why that is and how to eat spinach most safely.

First, What's the Deal with Oxalate and Kidney Stones?

Think of their relationship as "raw material" and "finished product."

What are kidney stones? Our urine contains many chemical substances that are normally dissolved in water and flushed out. But if the concentration of certain substances in the urine gets too high, or there's too little water (making the urine too concentrated), they can crystallize out, just like sugar that won't dissolve in over-sweetened water. These tiny crystals can slowly clump together, grow larger, and become "kidney stones."
What is oxalate? Oxalate (oxalic acid) is a natural compound found in many plants. Vegetables like spinach, celery, amaranth greens, and beets have especially high levels. It's not inherently bad, but it has one key trait: it loves binding with "calcium."
How do they come together? When oxalate enters our body and travels through the bloodstream to the kidneys to be excreted, if it encounters "calcium" in the urine, they bind together tightly to form "calcium oxalate." This substance doesn't dissolve in water and easily forms crystals—the most common type of kidney stone, calcium oxalate stones.

So, in theory, consuming too much oxalate can increase the risk of calcium oxalate crystallization in the urine.

So, Can I Still Eat Spinach?

Don't rush, it depends on the person:

For the vast majority of healthy people:

Eat it with confidence! Our bodies have strong regulatory abilities. As long as your kidney function is normal and your diet is balanced, an occasional plate of spinach is something your body can easily handle. Developing kidney stones is complex and has more to do with genetics, fluid intake, and overall diet (like eating too much salt and meat) than just spinach alone. Spinach shouldn't take all the blame.

Small tip: Even for healthy people, don't make spinach your staple food for every meal every day. Moderation is key for anything.

For those with a history of kidney stones or at high risk:

If you've already had calcium oxalate stones, or urine tests show elevated oxalate levels, then you need to be cautious. Doctors will usually recommend following a "low-oxalate diet." In this case, for "high-oxalate foods" like spinach, it's best to:

Eat less or avoid it.
If you really want some, always prepare it using the methods described below.

How to Eat Spinach "Smartly" to Minimize Risk?

These simple and effective methods are recommended for everyone, whether high-risk or not. They are good healthy habits:

1. Blanch it! Blanch it! Blanch it!

This is the most crucial step! Because oxalate dissolves in water, before stir-frying or making spinach salads:

Bring a pot of water to a boil, add clean spinach leaves, blanch for 1-2 minutes, then scoop the spinach out and pour away the blanching water!

This step removes 50%-80% of the oxalate in spinach, significantly reducing the risk. Then you can safely stir-fry, make salads, or use it in soups.

2. Pair it with "High-Calcium" Foods

That's right! For example, make "spinach and tofu stew" or drink a glass of milk while eating a spinach salad.

A common misconception is that "spinach + tofu" = "oxalate + calcium" = kidney stones. Actually, it's the opposite! When spinach and calcium-rich foods meet in the digestive tract, oxalate will bind with the calcium in the food, forming calcium oxalate. This calcium oxalate is not absorbed by the intestines. Instead, it passes straight through with your stool.

This way, far less oxalate enters the bloodstream to reach the kidneys, naturally leaving much less chance for it to cause mischief in the urine.

3. Drink Plenty of Water!

This is the "golden rule" for preventing all types of kidney stones. Drinking enough water dilutes your urine, lowering the concentration of both oxalate and calcium. Even if some calcium oxalate crystals do form, they are less likely to clump together and grow, making them easier to be flushed out by urine. Drinking 1.5-2 liters of water daily is more effective than anything else.

To Summarize

Healthy people: Eating spinach normally is fine. Cultivating the good habit of "blanching first" is even better.
High-risk individuals: It's best to eat less, as advised by your doctor. If you do eat it, you must "blanch first" and "drink plenty of water."
Don't avoid it unnecessarily: Spinach is a nutrient-rich powerhouse, packed with iron, vitamin K, folate, and dietary fiber. Using the right methods, we can safely enjoy its taste and nutritional benefits.