William Cole, IFMCP, DNM, D.C.

Functional Medicine Practitioner

By William Cole, IFMCP, DNM, D.C.

Functional Medicine Practitioner

Will Cole, IFMCP, DNM, D.C., is a leading functional medicine practitioner with a certification in natural medicine and a doctor of chiropractic degree.

Bushels Full of Apples

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February 9, 2023

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The more you learn about nutrition and bio-individuality, the more you realize that “eating healthy” isn’t always so black and white. In my telehealth functional medicine clinic, I walk patients through overcoming food sensitivities and personalizing diets that work for them, not necessarily everyone else.

One issue I see with some patients in my practice is oxalate sensitivity. Here’s what oxalates are, how to know if you’re sensitive to them, and how to tweak your diet accordingly—without cutting out plants entirely.


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What are oxalates? 

Oxalates are naturally occurring compounds found in a variety of fruits, vegetables, nuts, and legumes that work to protect plants from disease and insects. Oxalates are considered “anti-nutrients1” because when they are consumed by humans they can inhibit the absorption of other nutrients like iron and calcium.

When oxalates bind to the calcium, they end up forming calcium oxalate crystals, which can lead to diseases like rickets and osteomalacia. These calcium oxalate crystals can also travel through the body and contribute to chronic muscle pain and kidney stones2. A low-oxalate diet is one of the first tools used to prevent kidney stone recurrence.

Symptoms and causes of oxalate sensitivity.

The majority of people excrete oxalates through waste before they can pose an issue. However, those with oxalate sensitivities are thought to absorb more oxalate than they need or have trouble getting rid of excess oxalates. Oxalate sensitivity is not an official medical diagnosis, but I’ve personally seen it present in the following ways in my patients:

  • Abdominal pain
  • Bloating
  • Burning + tingling in your mouth and throat
  • Constipation
  • Diarrhea
  • Gas
  • Kidney stones
  • Muscle weakness
  • Nausea


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We still don’t know exactly what causes oxalate sensitivity, but some researchers believe it has to do with either leaky gut syndrome3 or mold toxicity4 (or both).

Functional medical doctors believe that leaky gut (also not currently a recognized medical diagnosis) occurs when your delicate intestinal lining is compromised. This causes undigested food particles and bacterial endotoxins to pass from the digestive system into your bloodstream and the rest of your body where it doesn’t belong. This can put your immune system in overdrive and lead to increased inflammation throughout your body. With this hyper-awareness, your immune system may end up reacting to almost any food that passes through, including healthy, high-oxalate foods like spinach.

Mold toxicity and mold-related diseases aren’t given the weight they deserve in conventional medicine, leaving many suffering for years without any answers. Since every person’s biochemistry is different, mold toxicity can manifest in various symptoms, especially considering the type of mold strain you are exposed to. Studies have shown a connection4 between people who were exposed to high levels of Aspergillus niger—a mold species often found in water-damaged buildings—and oxalate sensitivity due to the fact that this species of mold produces oxalate crystals.


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Foods that are high in oxalates.

These are some high-oxalate5 foods to watch out for if you have an increased risk of kidney stones or believe you are sensitive to oxalates:

  1. Beets
  2. Black pepper 
  3. Carrots
  4. Chocolate
  5. Chard
  6. Dates
  7. Oranges
  8. Kale
  9. Kiwi
  10. Legumes
  11. Nuts
  12. Potatoes
  13. Pumpkin seeds
  14. Radishes
  15. Rhubarb 
  16. Spinach
  17. Sunflower seeds
  18. Tofu
  19. Turnips


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Oxalates are present to some degree in most foods—particularly healthy plant foods. This means that you don’t need to give up oxalates altogether (and doing so can hold you back from your health goals).

Instead, I recommend staying below ~50 mg of oxalates per day (though everyone is different) if you suspect you have a sensitivity. This way, you’re still getting enough fiber and phytonutrients from plant foods that your body needs to thrive.

Foods that are lower in oxalates.

Foods are typically categorized into four different groups based on their oxalate content:

  • Very high: <100 mg per serving
  • High: 26–99 mg per serving
  • Moderate: 10–25 mg per serving
  • Low: 5–9 mg per serving


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  1. Bananas
  2. Apples
  3. Lemons
  4. Peaches
  5. Cabbage
  6. Mushrooms
  7. Zucchini
  8. Broccoli
  9. Cauliflower
  10. Eggs
  11. Meat
  12. Fish
  13. Poultry
  14. Cheese
  15. Milk
  16. Butter
  17. Coffee

You can also mitigate the oxalate content of high-oxalate foods by adding a few extra steps before eating. For example, studies have found6 that cooked vegetables have a lower oxalate content than raw ones. Soaking and cooking nuts, seeds, and legumes before eating can also reduce their oxalate content7.

The takeaway.

Even though oxalate sensitivity can come with a list of not-so-fun side effects, cutting out or cooking foods that are highest in oxalate may help with this uncomfortable issue. A functional medicine expert can run labs and complete a comprehensive health history to determine what is going on beneath the surface and walk alongside you during your healing journey.