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From a young age, we're told how important it is to eat our vegetables. What they don't tell us, however, is that some vegetables are high in oxalates, substances that can be harmful if they build up in our bodies.

If you're not familiar with the concept of oxalates, don't know how oxalates affect the body, or you're wondering whether you need to worry about them in your diet, we have the answers.

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Oxalates, also known as oxalic acid, are naturally occurring compounds found in certain plant foods. They can also be synthesized by the human body. The primary function of oxalates is to bind minerals, and they play a role in the formation of kidney stones.

Your GI tract absorbs oxalate from your foods. But, how much oxalate depends on the types of foods you eat.

Oxalate binds with minerals such as calcium and iron to form a solid compound, sometimes referred to as stone or crystals. These compounds are generally small and pass through your kidneys into your urine. When you urinate, these compounds exit your body.
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As mentioned, oxalates are naturally found in foods including the following:

• Spinach
• Kale
• Chard
• Rhubarb
• Almonds
• Tofu
• Cocoa powder
• Rice bran
• Raw hazelnuts

Foods high in oxalate can also contain compounds that can bind with iodine and affect its absorption. Iodine is one of the essential minerals required for making thyroid hormones. If your body doesn’t absorb enough, it can lead to iodine deficiency. Thus, potentially affecting thyroid function.

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Oxalate levels can build up in one of two ways: higher amounts of oxalates are absorbed in the GI tract or the body's ability to break down and eliminate oxalates is impaired. 

A 2020 study further explains what can cause oxalate to build up in your body:

• Genetics. Although rare, those with primary hyperoxaluria (high oxalate levels in your urine) have a defect in specific enzymes that can cause an overproduction of oxalate.
• Malabsorption issues. Those with a history of GI surgeries, inflammatory bowel disease, or malabsorption syndromes can increase oxalate uptake in the intestines. Researchers believe this is related to fat malabsorption, which can ultimately lower the amount of calcium available to bind to oxalate.
• Changes in the gut microbiome. Individuals with inflammatory bowel diseases have low amounts of oxalate-degrading bacteria commonly found in the gut. This has been linked to increased oxalate absorption as your body can’t break it down.
• Gut inflammation. When inflamed, oxalate can easily move between the cells of the GI tract and into your body. This is commonly referred to as a leaky gut.

Gut inflammation and microbiome alterations have been linked to triggering autoimmune disorders. Because of this, those with autoimmune disorders may be at a higher risk of oxalate buildup.

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In low amounts, oxalates usually won’t affect your body. However, high amounts may increase your risk of kidney stones.

Calcium oxalate compounds are the most common type of kidney stones. This occurs when oxalates, usually from dietary intake, bind with calcium in your body to form a solid “stone.” Normally, kidney stones are small, like a grain of sand, and easily pass through your kidneys, but sometimes they can’t. In these cases, kidney stones lead to pain and inflammation and can even prevent your kidney from functioning properly.

Calcium oxalate compounds are not only found in your kidneys; they have also been found in the thyroid. A 2019 study reported that almost 80% of autopsies they performed had calcium oxalate crystals in their thyroid.

A 2023 study reports that damaged thyroid cells release oxalate crystals. In turn, this can cause:

• Inflammatory reactions
• Oxidative stress
• Immune reactions

Both oxidative stress and inflammatory reactions have been linked to triggering autoimmune disorders like Hashimoto’s. Hashimoto’s affects your thyroid gland and is the number one cause of hypothyroidism (low thyroid hormone levels).

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"Oxalate dumping" is a condition that is thought to occur when you decrease your oxalate intake too quickly, causing the body to “dump” all your excess oxalate load. This rapid decrease causes symptoms such as:

• Dizziness
• Joint pain
• Fatigue
• Mood changes
• Muscle cramps
• Pain while having a bowel movement or urinating
• Skin rashes
• Trouble concentrating

The symptoms of oxalate dumping typically go away in a couple of days, up to several weeks.   

Since a build-up of oxalates may result in chronic inflammation, some believe those with an inflammatory-related condition like Crohn’s disease or rheumatoid arthritis may benefit from oxalate dumping. The thought is as your body gets rid of these symptoms and symptoms of your inflammatory-related condition will improve.

Keep in mind that the concept of oxalate dumping is based on anecdotal evidence. To date, there is no scientific evidence to support this concept.

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The good news is there are ways to reduce oxalate buildup that don't involve "dumping" and its associated symptoms. These include:

• Decreasing oxalate intake. Slowly decreasing oxalate in your diet helps prevent symptoms of oxalate dumping. Working with a nutritionist is the best way to reduce your oxalate intake.
• Increase calcium intake. Work with your healthcare provider to safely increase calcium intake through food sources or supplements. Higher calcium levels may help decrease oxalate absorption.
• Stay hydrated. Drinking water helps move oxalates out of your body.
• Watch your sugar intake. Those with high sugar intake may be at a greater risk for kidney stones.
• Cook those vegetables. Cooking vegetables that are high in oxalate can help lower the oxalate content.

Following a low-oxalate diet may benefit those with hypothyroidism or Hashimoto’s. By reducing your oxalate intake, your body can properly absorb iodine, potentially improving your thyroid hormone production. In addition, low oxalate diets may decrease inflammation, prevent kidney stones, and help with weight loss.

Starting a low-oxalate diet may be trickier than you think. Oxalate-rich foods are healthy and, in some cases, have been shown to benefit those with autoimmune disorders. Like with most diets, it is about finding the right balance. Our nutritionists here at Paloma Health can help you find the right balance of oxalates without depleting other essential nutrients. Set up an appointment with one of them today.

What foods are high in oxalates?

Spinach, kale, chard, rhubarb, almonds, tofu, cocoa powder, rice bran, and raw hazelnuts are all naturally high in oxalates. These foods can also contain compounds that bind with iodine, which may affect how much iodine your body absorbs.

Can oxalates affect thyroid function?

Yes, in a couple of ways. Foods high in oxalate can bind iodine and reduce its absorption, and iodine is needed to make thyroid hormones. Calcium oxalate crystals have also been found in thyroid tissue, and damaged thyroid cells may release oxalate crystals that trigger inflammation and immune reactions linked to autoimmune conditions like Hashimoto’s.

What is oxalate dumping?

Oxalate dumping is a term for symptoms some people report when they cut oxalate intake too quickly, such as dizziness, joint pain, fatigue, mood changes, and skin rashes. The concept is based on anecdotal reports, and there is currently no scientific evidence confirming it.

How long do oxalate dumping symptoms last?

When reported, these symptoms typically resolve within a couple of days, though some people describe them lasting up to several weeks.

How can I lower my oxalate levels without triggering dumping symptoms?

Reducing oxalate intake gradually rather than all at once, increasing calcium intake with guidance from your healthcare provider, staying well hydrated, watching your sugar intake, and cooking high-oxalate vegetables can all help lower oxalate levels more gently.