Dr Alex Petrushevski
Oxalates are natural compounds that are found in a wide variety of plant foods in the form of oxalic acid, where they are synthesized by the incomplete oxidation of carbohydrates. As with other plant toxins they help protect plants against predators like animals, insects, and harmful bacteria. They’re often referred to as “anti-nutrients” due to their affinity for binding to minerals.
When ingested in humans, oxalic acid combines with other ions to form crystals (eg. Calcium oxalate). They are typically then excreted in urine as minute crystals, as they serve no physiological purpose. Unfortunately, if ingested in excess they can cause a variety of medical issues. The most common condition is kidney stones – The most prevalent type of kidney stones are calcium oxalate stones.
Oxalates have been implicated in a variety of diseases and functional disorders including:
– Inflammatory disorders
– chronic pain / arthritis
– autoimmune disease
Oxalate crystals have also been shown to damage nerve cell structures, and to accumulate in the thyroid gland over time.
Oxalates are difficult to study and measure in humans due to their crystal structure – there is no easy blood test to determine a person’s circulating oxalate level.
Foods high in oxalates include:
- Spinach (very high)
- Rhubarb (very high)
- Soy products / tofu (very high)
- Black tea
- Potato / sweet potato
Some helpful tips for minimising the risk of oxalate stones and other oxalate related problems include:
- Boil high-oxalate leafy greens before eating, and discard the water
- Eat adequate calcium in your diet. Calcium binds to oxalate in the gut and limits how much you actually absorb
- Drink plenty of fluid. Diluting your urine can help reduce the risk of calcium oxalate kidney stones
- Avoid ingesting large amounts of high oxalate foods at once – spinach smoothies are out!
- Above all else, try to emphasise animal proteins in your diet – animal products like meat, dairy and eggs contain negligible amounts of oxalates and are also generally more nutrient dense foods without any of the anti-nutrients that stop you from absorbing what you need to stay healthy
This article provides general information from the current scientific evidence base and clinical judgement of the author. It is designed for educational purposes only and should not be substituted for medical advice. The author recommends you seek personally tailored support from a qualified healthcare practitioner before undertaking any major lifestyle change.