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Are Healthy Foods Making You Sick? You Might Be Consuming Too Many Oxalates

Written by: Joanne Kennedy, Executive Contributor

Executive Contributors at Brainz Magazine are handpicked and invited to contribute because of their knowledge and valuable insight within their area of expertise.


Some are good, so more must be better when it comes to healthy foods, right? This is a common misconception people often make when it comes to health, but overconsuming so-called “superfoods” could actually harm your health.

Wooden table and wooden spatula with different kind of nuts.

We are seeing more and more clients who are feeling worse when they eat well and the reason for this is oxalates. Found in many healthy fruits and vegetables with high antioxidant content, oxalates can cause damage to our digestive tract and other body tissues if consumed in excess.

Science has known about the toxic effects of oxalates on human health since the 1800’s. This is why we know that certain plants are poisonous and should not be consumed. As food science evolved in the 1900’s to focus on the isolated nutrient content of foods, our awareness of oxalates became forgotten until now.

This article will highlight the reasons oxalates have become so problematic for humans in the last few decades and why moderation is key.

What are oxalates?

Oxalic acid is a naturally occurring, non-nutritive molecule in many plants. When oxalic acid is bound with minerals, it forms microscopic oxalate crystals that are very sharp and abrasive.

Oxalates are poison and the body eliminates them to protect cells and tissues from damage. If intake is too high to be excreted, oxalates will be absorbed from the gut into the blood and then deposited into tissues and organs. The most well-known oxalates are calcium oxalate stones found in the kidneys, known as kidney stones. Even tucked away in “storage,” these oxalates can do damage.

How oxalates are harmful

The abrasiveness of the crystals makes them an irritant that damages the lining of the gastrointestinal tract leading to a multitude of gut symptoms and food intolerances. Once in the blood, oxalates can cause physical damage to cells that disrupt general function, energy production, cellular repair and maintenance. This damage triggers the immune system leading to increased inflammation and oxidative stress.

Oxalates also have the capacity to bind to important nutrients in the gut, making them unavailable for absorption. Deficiencies in calcium, magnesium, potassium, iron, sulfur and B vitamins are common. Depletion of antioxidants such as glutathione occurs as the body works hard to combat oxidative stress.

What are the high oxalate foods?

Many foods labeled as modern “superfoods” for their antioxidant content are also high in oxalate, making it easy to accumulate high levels in the diet. Consuming the following foods regularly could lead to an intake 10x higher than the excretion capacity of the body, leading to a host of symptoms.

Vegetables: spinach, sweet potato, celery, carrot, rhubarb, swiss chard, beetroot, potato

Fruit: raspberries, blackberries, kiwifruit, starfruit, figs

Nuts and Seeds: sesame seeds, almonds, cashews, walnuts, macadamia nuts, pine nuts

Spices: turmeric, cinnamon

Grains: buckwheat, millet, rye, wheat

Other: black tea, cacao, milk thistle, soybeans, navy beans

What are the symptoms of oxalate toxicity?

Symptoms can be very varied and affect any organ or tissue. They can come and go randomly, making it difficult to determine potential causes or triggers:

  • Digestive symptoms include reflux, abdominal pain, bloating, excess belching, loose stools

  • Neurological symptoms include headaches, fatigue, anxiety, insomnia, depression

  • Musculoskeletal symptoms include muscle soreness or tightness, joint pain, injuries that don’t heal, tendonitis, connective tissue disorders, cysts, fibrosis, osteopenia or osteoporosis

  • Urinary symptoms include Irritable bladder, frequent urination, pelvic discomfort, cloudy urine, vulvodynia, interstitial cystitis, frequent UTIs

What is contributing to oxalate issues?

High oxalate diet

The biggest contributor to oxalate toxicity is excessive intake. Modern food systems allow us to enjoy foods all year round in quantities not available to our ancestor's hundreds of years ago. Nuts, seeds, cacao and berries that were once an occasional food are now being consumed in high quantities daily in the form of smoothies, baking flours, nut spreads and bliss balls in an attempt to be healthier.

Poor gut health

An unhealthy gut will allow more oxalates to enter the bloodstream than a healthy gut. Inflammation, impaired gut barrier function, fat malabsorption, constipation, or diarrhea can all lead to an increase in oxalate absorption. This means the body can tolerate less oxalate in the diet compared to someone with a well-functioning gut.

A healthy balance of gut bacteria is also important – Oxalobacter formigenes is a gut bacteria that are capable of breaking down oxalates in the diet. Without sufficient levels of this bacteria, the body must work harder to excrete oxalates. A diet very high in oxalate will disrupt this bacteria, leading to a reduction in numbers.

Vitamin C supplementation

It has become increasingly popular to supplement with large quantities of vitamin C for antioxidant potential and immune health. When the body metabolises ascorbic acid, it’s recycled into oxalic acid which then needs to be dealt with. Daily supplementation above 250mg will increase oxalic acid in the body.

How to enjoy plants foods without oxalate excess

  • Eat seasonally rather than consuming the same foods all year round

  • Include variety in the diet

  • Enjoy a wide range of low oxalate vegetables

  • Avoid baking with nut flours

  • Enjoy very high oxalate foods occasionally and in small amounts

  • Boil high oxalate vegetables to remove some of the oxalates into the water (discard the water afterward)

  • Drink black tea with milk to minimise absorption

  • Consume calcium with high oxalate foods to bind to oxalate for excretion

The focus on food as a whole has been forgotten in preference of focusing on individual constituents and nutrients. A diet of moderation and variety is key to minimise damage from oxalates.

When reducing oxalate intake, it is important to do so gradually; the body will begin to release stored oxalate from tissue that can temporarily worsen symptoms. It is recommended to work with an oxalate literate practitioner to assist in the transition to keep symptoms to a minimum.

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Joanne Kennedy, Executive Contributor Brainz Magazine

Joanne Kennedy is a Naturopath and specialist in methylation, histamine intolerance, gut health, and women’s hormones. Joanne runs a successful clinical practice in Sydney, Australia and sees patients online worldwide. Joanne’s approach is to identify the root cause of illness. This is done by the use of functional pathology testing, assessing the biochemical individuality of each patient, assessing environmental exposures, as well as individual genetic testing if required.



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