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What if some of the “healthiest” foods on the planet are actually harming your health? This may sound crazy, but foods like spinach and almonds have features that can wreak havoc on your health if eaten excessively.
This harsh reality can get lost in the mix of mainstream health headlines and lead to a host of serious health issues despite eating “healthy.”
In particular, oxalates are found in vegetables, nuts, seeds, and certain fruits. While these foods can certainly be beneficial, oxalate overload can silently take a toll on your body.
This article will look at the major sources of oxalates, explore why they can be so damaging, and answer the question, are oxalates bad for you?
What are Oxalates?
Oxalate (oxalic acid) is an organic acid produced by plants and is typically found in the leaves, seeds, stems, and bark (1). Oxalates play an important role for plants, helping with growth, heavy metal detoxification, and pH regulation (2). However, there is no known use for oxalates in humans (3).
Oxalates are an antinutrient, meaning they can bind to minerals like magnesium, iron, and calcium, reducing their absorption by the body (4).
These foods are the main sources of dietary oxalate in the human diet (5).
The human body can also create oxalates in the liver and kidneys (6).
The kidney is tasked with oxalate excretion from the body, but humans don’t have the ability to process oxalates (7, 8). Still, oxalates can be removed from the body through feces, urine, or with the help of certain microorganisms in the gut (oxalobacter formigenes) (9).
For a healthy person, an estimated 95% of oxalate from food and the body is removed through urine (10).
Oxalate has two primary forms: soluble and insoluble. Insoluble oxalates are tough to absorb and considered less harmful (11, 12). Soluble oxalate can find its way into the bloodstream and accumulate in the kidneys (13, 14).
The ability to absorb oxalates can differ greatly on an individual basis depending on diet, gut health, mineral status, fat malabsorption, and genetic mutations (15, 16, 17, 18, 19). Excessive intake or oxalate absorption can lead to serious consequences.
Are Oxalates Bad For You?
Are oxalates bad for you? The short answer is that it depends. Different lifestyle habits, genetics, or health disturbances can alter the way your body handles oxalate absorption.
In general, excessive consumption and absorption of oxalates can be fatal for both animals and humans or contribute to kidney failure, hyperoxaluria, cardiomyopathy, and other serious challenges (20, 21).
Kidney Health
Oxalate in the urine is a powerful promoter of kidney stones (22). The most common type of kidney stone (calcium oxalate) occurs mainly due to an imbalance between oxalate and calcium (23).
For someone with healthy kidney function, normal oxalate intake (around 100-200 mg per day) is assumed to be harmless (24). But, oxalate deposits can lead to kidney damage which is the main organ responsible for oxalate excretion (25).
Kidney disease, which affects over 30 million Americans, may hinder the removal of oxalates, potentially impacting every organ in the body (26, 27).
Cardiovascular Health
The cardiovascular system can also be negatively affected by oxalates:
- A high oxalate diet is a main cause of secondary hyperoxaluria (high levels of oxalate in the urine), which is a risk factor for cardiovascular dysfunction (28).
- Too much oxalate in the body (hyperoxalemia) can increase the risk of cardiovascular disease.
- Complications from oxalates may even be connected to strokes and coronary heart disease, which may share similar developmental processes to urinary stones (29, 30).
Again, many people can handle oxalates without issue. But, some are more at risk for complications due to genetics, diet, and other factors.
Who Should Be Cautious of Oxalates?
Those on a vegan or vegetarian diet may consume far higher levels of oxalate due to an increased vegetable intake (31). Calcium intake may also be low in plant-based dieters due to limiting or removing dairy products.
Women are also more likely to avoid red meat while embracing vegetables. At the same time women are susceptible to iron and calcium deficiencies; both of these minerals can be negatively impacted by oxalates (32).
For both men and women, obesity is associated with higher levels of oxalate in the urine (33). Urinary oxalate concentration can also be increased by antibiotic or diuretic usage, dehydration, and inflammation (34).
Inflammatory bowel disease (IBD) patients regularly struggle with kidney stones and are at an increased risk of oxalate toxicity (35, 36). High levels of oxalate in the body can also be found in common gut issues like irritable bowel syndrome (IBS), celiac disease, or Chron’s disease (37, 38).
High Oxalate Foods: Be Aware of These!
In general, oxalate levels are highest in the leaves, followed by the seeds and stems, while animal foods contain practically zero oxalates (39, 40). So, oxalates are typically found in vegetables and in certain fruits like starfruit, elderberry, and dried figs (41).
Vegetables such as spinach and rhubarb, nuts, seeds, tea, and grains like amaranth tend to be highest in oxalates (42, 43). A typical portion of spinach can give you 500-1000 mg of oxalate (44)!
It’s worth mentioning that the oxalate content of the same food can vary greatly based on several factors. For example, a package of spinach grown in California may differ greatly in oxalate content compared to spinach grown in China.
Plant oxalate content can vary depending on variety, seasonality, fertilizer usage, ripeness, and the calcium content of the growing location (45, 46). Tea can also be high in oxalates, but the content can be determined by the type of tea, tea quality, origin, and brewing time (47).
Thankfully, oxalates can be removed (or reduced) from foods thanks to specific preparation methods.
How to Reduce Oxalates In Food
It is nearly impossible to completely avoid oxalates and other plant defense chemicals, but the burden can be reduced with proper preparation and the utilization of minerals like magnesium and dietary calcium.
In order to reduce the levels of soluble oxalates (considered most harmful) consider soaking, boiling, or steaming high oxalate foods (48). As a general rule of thumb, vegetables can be cooked to lessen oxalate content, while nuts, beans, or seeds should be soaked (49).
You can also take other precautions to fend off the dangers of oxalate consumption.
1. Embrace Magnesium and Calcium Intake
Both calcium and magnesium can bind to oxalates, reduce the absorption, and lower the health risk of oxalate overload (50, 51). Unsurprisingly, a diet low in calcium is considered a key risk factor for oxalate stones (52).
Calcium rich foods such as milk, yogurt, and cheese can be helpful additions to counteract this risk.
2. Monitor Vitamin C
When the human body creates oxalates, vitamin C is a main part of this process (53, 54). Those with calcium oxalate stone disease may be encouraged to stop taking vitamin C supplements and monitor their intake of foods rich in vitamin C (55, 56).
3. Eat Seasonally
Depending on where you live, high oxalate foods like spinach or almonds may only be available for a few months out of the year. Eating seasonally may help you avoid eating high-oxalate foods year-round and avoid the complications of excessive oxalate consumption.
Check out this seasonal food guide to figure out what’s in season in your area.
4. Work With a Medical Professional
Given the complex interactions between gut health, mineral balance, and other factors, working with a medical professional can help avoid complications from oxalate sensitivity.
5. Choose Low Oxalate Foods
A low oxalate diet may not always be feasible, but it may be able to reduce urinary oxalate in kidney stone formers (57). Here’s a list of popular low oxalate foods (58):
The Bottom Line: Exercise Caution Around Oxalates
Even with the drive to eat healthy, overlooked dangers can lurk where you least expect them. When most people think of spinach, chia seeds, or other plant foods, they think they’re making a healthy choice.
But, for some people, these foods can spell trouble thanks to their oxalate content.
For many, oxalates are completely harmless. But, with the widespread levels of disease around the globe, oxalates can rapidly turn into a major concern, contributing to kidney stones, gut issues, and poor cardiovascular function.
Placing an emphasis on animal foods, fruits, and other components of an animal-based diet, you can not only limit oxalates, but also consume some of the most nutritious foods on the planet.
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