Should You Really Be Afraid of Oxalates?

Oxalates are one of the newest villains in the nutrition world.

I know because I used to be afraid of them too.

Several years ago, I avoided potatoes because I had heard they contained oxalates. Not because I had any symptoms or issues with potatoes. But because I was told oxalates were bad.

Potatoes contain oxalates. Therefore potatoes = bad.

And while it’s true that certain modern health trends have pushed oxalate intake much higher than what most people would historically consume (think raw spinach smoothies, almond milk and almond flour everything, green juices, and giant raw spinach salads), I’ve also watched (and felt) the pendulum swing too far in the opposite direction.

Now, I see people afraid of almost any food that contains oxalates.

Potatoes, sweet potatoes, tea, berries, chocolate, leafy green vegetables, and other foods commonly labeled as "high oxalate foods".

Foods that many people can enjoy without any issues at all.

To be clear, I am not dismissing people who genuinely feel better with lower oxalate intake. Individual responses certainly matter. Oxalate intolerance is real. Kidney stones are real. But context matters.

I also don’t think most people need to live in fear of every food containing oxalates. Because oxalate exposure is far more complicated than looking up a food on a list.

Let’s talk about why.

What Are Oxalates and Why Are People Concerned About Them?

Oxalates are natural compounds found in plants that have the ability to bind with calcium. When enough calcium and oxalate are present together, they can form tiny calcium oxalate crystals. Most of the time, your body handles this process just fine and is able to detoxify oxalates. But under the right conditions, those crystals can grow, clump together, and eventually form kidney stones.

So most concerns revolve around calcium oxalate kidney stones, which account for roughly 70-80% of all kidney stones. And yes, kidney stones are a legitimate health concern!

But here’s where the conversation often gets oversimplified. People hear that oxalates can contribute to kidney stones and immediately assume: “Oxalates are bad.”

But whether oxalates become a problem depends on far more than simply whether a food contains them.

Your Body Makes Oxalates Too: Understanding Endogenous Oxalate Production

Most people assume oxalates only come from food.

Not true.

Your body also produces oxalates on its own (ref), a process known as endogenous oxalate production. Some researchers argue that endogenous production may be one of the largest contributors to a person’s total oxalate burden. (ref)

As one review states: (ref)

“Endogenous oxalate synthesis makes an important contribution to the amount of oxalate excreted in urine and hence the development of calcium oxalate kidney stones.”

What I find especially interesting is that your metabolic state influences this process. (ref)

Meaning, endogenous oxalate production isn’t simply a matter of what you eat. The body can generate oxalates internally through normal metabolism, and poor metabolic health can increase that production.

So before we even look at a spinach leaf or a potato, it’s important to understand that your oxalate burden isn’t determined solely by dietary intake.

Why Oxalate Food Lists Are More Complicated Than They Look

The internet often treats oxalate content as a fixed number (as if every spinach leaf contains the exact same amount.)

But in reality, oxalate content of foods can vary substantially depending on:

• - Variety
• - Growing conditions
• - Soil fertility
• - Climate
• - Plant maturity
• - Harvest timing

For example, one study found that the soluble oxalate content of green tea ranged from 8.3 mg/L to 139.8 mg/L depending on when the tea was harvested. (ref)

Another study found nearly an 80% difference in spinach oxalate content depending on cultivar, season, and growing environment. (ref)

Researchers have also reported tremendous variation in foods such as spinach, rhubarb, and beets, with published values differing by several hundred milligrams per 100 grams. (ref)

While yes, some foods are generally higher in oxalates than others, there is no single oxalate value for many foods.

Which is one reason online oxalate lists can be so confusing, often conflicting with one another and leaving people wondering what they’re actually supposed to eat.

The reality is that oxalate exposure is much more dynamic than most lists make it seem.

Raw vs. Cooked Oxalates: Why Preparation Matters

Another thing many oxalate lists ignore is how people actually eat food.

Most laboratory analyses measure foods in their raw form.

But traditionally, many higher-oxalate foods weren’t eaten raw.

They were:

• - Boiled
• - Stewed
• - Fermented
• - Cooked and served with other foods

And that matters a lot!!

Oxalates are water-soluble. So when vegetables are boiled, a significant portion of the soluble oxalate content leaches into the cooking water.

Research consistently shows that boiling can substantially reduce soluble oxalates (ref), the fraction most relevant to absorption and kidney stone risk.

A giant raw spinach smoothie is not metabolically equivalent to cooked spinach served as part of a meal.

Preparation and the full meal matters. We don’t eat nutrients, or oxalates, in isolation. How a food is prepared and what it’s eaten with can significantly impact how much oxalate your body ultimately absorbs.

How Calcium Reduces Oxalate Absorption

This may be the most overlooked piece of the entire conversation.

Calcium binds oxalate in the digestive tract, so less oxalate gets absorbed.

In the figure below, you can see how there is significantly less oxalate absorbed when dietary calcium intake is at 1,200 mg and above. (ref)

In fact, dairy consumption is associated with a significantly lower risk of kidney stones (ref), likely because of its calcium content.

A question I rarely see asked is:

How much calcium are people consuming alongside their oxalates?

Because that matters, a lot.

If you’re especially concerned about oxalates, consuming calcium-rich foods in the same meal can help reduce absorption.

Nutrients That Support Oxalate Metabolism and Detoxification

Your body has natural pathways for processing and eliminating oxalates, and those pathways require nutrients to run properly.

So there are other nutrients in addition to calcium that can help support this process.

This is one reason I focus so heavily on nutrient density and making sure I hit the RDAs for vitamins and minerals through whole food sources.

These nutrients aren’t just “nice to have.” They serve as cofactors that allow enzymes to carry out the countless metabolic reactions occurring inside your body every second.

Enzymes run the show in our bodies. They help convert food into energy, process toxins, build and repair tissues, regulate hormones, and support virtually every aspect of metabolism.

But enzymes require nutrient cofactors to perform their metabolic tasks, meaning they cannot function optimally without adequate amounts of specific vitamins and minerals.

When the appropriate nutrient cofactors are present in sufficient concentrations for enzymes to operate fully, the food we eat is successfully metabolized into useful end-products and cellular energy is produced.

When these nutrient cofactors are in short supply because we aren’t consuming enough vitamins and minerals, metabolic pathways become less efficient, making it harder for the body to properly process, detoxify, and eliminate compounds that are naturally produced through metabolism.

Time and time again, research shows that vitamins and minerals consumed within a whole-food matrix often outperform isolated compounds found in supplements.

Yet many people spend enormous amounts of energy worrying about oxalates while simultaneously failing to meet their basic vitamin and mineral requirements (something you can easily assess by tracking a few days of eating in an app like Cronometer).

Before stressing about the oxalate content of every food, it may be worth asking a simpler question: Am I giving my body the nutrients it needs to handle oxalates in the first place?

Can PUFAs Increase Endogenous Oxalate Production?

This entire article was inspired by a YouTube comment on one of my full day of eating videos.

And honestly? I kind of do!

Here’s why.

Researchers have described glyoxal as one of the most important sources of endogenous oxalate synthesis in humans. (Meaning, the more glyoxal your body produces, the more oxalate it has the potential to produce internally.)

Now glyoxal doesn’t only come from one place in the body. But one source is the oxidation of polyunsaturated fatty acids (PUFAs).

Because of their multiple double bonds, PUFAs are highly susceptible to oxidation. During this process, compounds called lipid peroxides are formed, and one of the breakdown products generated is glyoxal (ref). Numerous studies have identified glyoxal among the oxidation products of Omega 6 fats like linoleic and linolenic acids (ref, ref, ref). Other research has shown that reducing PUFA peroxidation can reduce calcium oxalate crystal deposition in the kidneys. (ref)

Which highlights another reason why your dietary fat choices are important. The more PUFA stored in membranes and adipose tissue, the more substrate is available for lipid peroxidation. After all, you can’t oxidize what isn’t there. This is one reason lipid peroxidation products rise when membrane unsaturation increases. So, greater PUFA availability combined with greater oxidative stress may increase glyoxal formation through lipid peroxidation.

You will notice in this figure from (ref) that researchers have identified multiple routes that can generate glyoxal, including both the oxidation of polyunsaturated fats and pathways related to glucose metabolism.

This ties back to something I mentioned earlier in the article: your metabolic state influences endogenous oxalate production.

The researchers are not saying ‘glucose cause oxalates’. The concern is dysregulated glucose metabolism seen in diabetes and metabolic syndrome. (Which PUFAs can contribute to since PUFAs disrupt the body’s ability to burn glucose efficiently by inhibiting enzymes essential for breaking down carbs (r,r).)

In addition to the glyoxal pathway, there is also emerging evidence that ferroptosis, a form of cell death driven by lipid peroxidation of PUFAs, may contribute to kidney stone formation and crystal deposition. (ref)

None of this proves that dietary PUFAs are the primary cause of oxalate problems.

But it does highlight that oxalate production is influenced by much more than simply how many oxalates you consume.

Supporting metabolic health through regular exercise, maintaining muscle mass, consuming a nutrient-dense diet, and being mindful of the types of fat in your diet may all influence the body’s endogenous oxalate burden.

And this is where I think the conversation around oxalates sometimes misses the bigger picture.

Oxalates are a natural compound found in many foods that humans have consumed throughout history. Potatoes, berries, seasonal greens, chocolate, tea, and countless other foods naturally contain oxalates.

By contrast, the dramatic increase in omega-6 polyunsaturated fats (particularly linoleic acid from industrial seed oils and conventional chicken/pork) is a relatively recent change in the human diet. Modern linoleic acid consumption is estimated to be several times higher than it was just a century ago and far higher than what our ancestors would have consumed for most of human history. So while many people are busy stressing over naturally occurring compounds found in whole foods, they may be overlooking one of the most significant dietary fat shifts of the modern era.

If you’d like to learn more about how high-PUFA diets impact metabolism, oxidative stress, and long-term health, you can read my full article on the health consequences of a high-PUFA diet here.

This PUFA discussion is just another reason why I tend to focus on overall metabolic health rather than obsessing over the oxalate content of individual foods.

Seasonal Eating and Oxalates: Why Exposure Naturally Changes Throughout the Year

Another reason I don’t obsess over oxalates?

Seasonality.

Nature rarely gives us the same produce options all year long.

Historically, people naturally cycled through different fruits and vegetables as the seasons changed. Spring greens. Summer berries. Fall squashes. Winter storage foods.

Produce availability shifted throughout the year. And with it, oxalate exposure likely shifted too! Today, we can eat spinach every day of the year if we choose. But is that really normal?

One of the benefits of seasonal eating is that it naturally creates dietary diversity since you aren’t eating the same produce year-round.

You rotate foods and as a result, you naturally rotate your exposure to different nutrients, plant compounds, and yes, even oxalates.

Instead of consuming the same handful of foods every day for years on end, your diet changes throughout the year as different produce options come into season. Learn more about how I approach seasonal eating and the health benefits in a previous article I wrote, here.

Now, you don’t need to reinvent your diet every week. But shifting some of the fruits and vegetables you eat from season to season can make meals more enjoyable and increase dietary diversity.

Nature doesn’t serve us spinach smoothies every day of the year. And maybe that’s a good thing.

Personally, I cycle through produce options as the seasons change and don’t stress about the fact that my oxalate intake naturally fluctuates throughout the year.

What I do try to keep consistent is eating a nutrient-rich diet and getting plenty of dietary calcium every day (I monitor this using Cronometer).

To me, that’s a much more practical approach than obsessing over the oxalate content of every fruit and vegetable I eat.

Should You Be Afraid of Oxalates?

The internet often treats oxalates as though they’re a fixed toxin hiding in food.

The reality is much more nuanced.

Oxalate exposure is influenced by:

• - How foods are grown
• - How they’re prepared
• - What they’re eaten with
• - Your nutrient status
• - Your metabolic health
• - Even the time of year

I am not here to tell you to start drinking spinach smoothies made with almond milk every day. Nor am I here to tell you that everyone should ignore oxalates.

But most people don’t need to fear oxalate-containing foods. A person drinking a giant raw spinach smoothie with very little calcium is in a very different situation than someone eating cooked vegetables as part of a nutrient-rich meal.

Gauge your individual tolerance, and eat a well-rounded diet rich in vitamins and minerals.

Personally, I focus on eating a wide variety of foods, rotating produce with the seasons, meeting my micronutrient needs, and consuming plenty of calcium-rich foods throughout the year.

I don’t fear oxalates. I understand them.

And in nutrition, understanding is almost always more helpful than fear!

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Frequently Asked Questions About Oxalates

Are oxalates bad for everyone?

No. Oxalates are natural compounds found in many plant foods. While some individuals may benefit from limiting high-oxalate foods, most people can consume oxalate-containing foods as part of a nutrient-rich diet without issue.

Does the body make oxalates on its own?

Yes. Oxalates are not only obtained from food. Your body also produces oxalates through metabolic processes, a phenomenon known as endogenous oxalate production.

Does cooking reduce oxalates?

Often, yes. Boiling can significantly reduce the soluble oxalate content of many vegetables because oxalates can leach into the cooking water.

Does calcium reduce oxalate absorption?

Yes. Calcium binds to oxalate in the digestive tract, reducing the amount that is absorbed into the bloodstream. Consuming calcium-rich foods alongside higher-oxalate foods is one of the best ways to reduce oxalate absorption.

What foods are highest in oxalates?

Foods commonly considered higher in oxalates include spinach, beet greens, Swiss chard, rhubarb, almonds, and certain teas. However, oxalate content can vary substantially depending on growing conditions, harvest timing, and preparation methods.

Should I avoid potatoes because they contain oxalates?

For most people, no. Potatoes contain oxalates, but they also provide valuable nutrients such as potassium, vitamin C, B vitamins and healthy carbohydrates. Whether a food contains oxalates is only one factor to consider when evaluating its place in a healthy diet. It's always best to gauge individual tolerance and digestibility.