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Are Oxalates Messing with Your Gut?

Eating a diet rich in fresh fruits and vegetables including leafy greens, is generally crucial for staying healthy and in particular, keeping the gut microbiome happy. 

However, eating large amounts of a certain group of green vegetables can bring on unwanted side effects. These are what we refer to as high-oxalate foods which can be extremely triggering for those with oxalate-sensitivities.

What Are Oxalates?

Oxalates, also known as oxalic acid or oxalate salts, are naturally occurring compounds found in many plant foods and are also produced by the human body.  They cannot be digested by our bodies, but in a healthy digestive system, they can be metabolised by good gut bacteria and excreted as a waste product in the stool.

They are found in a wide variety of plant-based foods, including spinach, rhubarb, beets, Swiss chard, cocoa, tea, nuts, and some fruits like blackberries and raspberries.


Why Can They be Problematic?

While oxalates themselves are not harmful, they can form insoluble crystals when they combine with minerals like calcium, sodium, magnesium and potassium.

The most common issue that arises from the poor metabolism of oxalates is the formation of kidney stones, but the oxalate crystals can accumulate in any tissue around the body. These sharp-edged oxalate crystals can be inflammatory and can contribute to conditions like arthritis, heart abnormalities, kidney stones and fibromyalgia.

In addition, oxalates can cause:

Increased pain and inflammation

Oxalates increase oxidative stress and inflammatory cytokines, causing inflammation and exacerbating existing pain.

Mineral deficiency

If there are excess oxalates in the body, minerals such as magnesium, iron, calcium and zinc bind together with oxalates to form deposits often resulting in depletion of minerals.

Antioxidant depletion

Oxalates cause oxidative stress, depleting our antioxidant compounds like glutathione that are important in regulating immune function, liver detoxification and inflammation.

Mitochondrial damage

Mitochondrial health and normal mitochondrial function can become significantly impaired when exposed to high amounts of oxalate. Over time, mitochondrial dysfunction can lead to mitochondria damage, impacting your body’s ability to generate energy. 

Sulphur intolerance

Oxalates complete with sulphates for absorption into the cells, so high levels of oxalates can deplete sulphate levels and contribute to sulphur intolerance. 


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Symptoms of Oxalate Sensitivity

  • Pelvic/urinary irritation
  • Frequent UTIs
  • Kidney stones
  • Joint pain
  • Tight muscles
  • Anxiety and moodiness
  • Brain fog
  • Insomnia
  • Fatigue
  • Reflux
  • Skin sensitivities
  • Rashes
  • Food reactions
  • Low iron levels
  • Thyroid issues 

What Causes Oxalate Sensitivity?

Most people are not sensitive to oxalates as they are able to metabolise and expel most of the oxalates from their body. However, problems arise if the body absorbs more oxalates than it should or has difficulty metabolising it. This leads to an accumulation of oxalates over time, resulting in an intolerance (or sensitivity) towards oxalates. 

The main causes of oxalate toxicity are:

Poor gut microbiome balance

A healthy gut microbiome is responsible for maintaining oxalate homeostasis in the body. If the gut microbiome is out of balance due to poor diet or overuse of antibiotics, this can cause a build up of oxalates.

Increased intestinal permeability or ‘leaky gut’

If the intestinal lining is inflamed and more permeable, oxalates are able to be easily absorbed through the intestinal barrier, leading to an accumulation of oxalates in the body.

High intake of oxalates

Overconsumption of high oxalate foods such as spinach, beetroot and kale can exceed the ability of the body for excretion, leading to accumulation in tissue.

Nutrient deficiencies

A depletion of vitamin B1 or B6 can lead to increased production of oxalic acid, increasing the total body burden.

Fat malabsorption

Poor digestion of fats and bile acids can reduce calcium available to binding with oxalates, thereby increasing oxalate levels.

Mold Exposure

Aspergillus niger, a toxic mold from water damaged buildings, produces oxalates during their fermentation process. People who have been exposed to water-damaged buildings affected by mould are likely to have high oxalate levels in their bodies.


How to Reduce Oxalate Sensitivity

While progressing towards eliminating the foods that are extremely high in oxalate, there are other habits you can implement that may ease the symptoms if you do end up consuming a food high in oxalate. That includes reducing and managing your stress, decreasing your intake of foods high in oxalate, and being aware of habits that might worsen the condition. It’s also vital that you aim to decrease your intake of vitamin C, as this may transform into oxalate in your system.


Healing from oxalate sensitivity or toxicity involves a multifactorial approach, but the easiest place to start is to consume less of it! Avoid greens such as spinach and Swiss chard as well as nuts, legumes and dark chocolate, opting instead for low-oxalate foods (Google is your friend here). Another way to reduce oxalate levels from your vegetable intake is to cook your vegetables, which has been shown to decrease oxalate levels by up to 87%. 

Increase calcium intake

Increasing your intake of calcium through your diet or supplementation can reduce symptoms significantly. Calcium has been shown to reduce the absorption of oxalates and therefore the health problems associated with oxalates.

Limit vitamin C intake

When vitamin C is metabolised, it produces oxalates as an end product, so large amounts of vitamin C is not recommended if you're suffering from oxalate sensitivity. Limit your vitamin C intake to no more than 500mg per day.  

Heal your gut

Healing your gut is probably most fundamental in addressing oxalate sensitivity. While one can generally build up a healthy, balanced microbiome by adopting an active, lower stress lifestyle and a diet with the right probiotics, lots of bone broth, fermented foods and healthy fats, oxalate sensitivity tends to arise as a result of more serious gut disorders such as intestinal permeability.

If you experience frequent bloating after eating or other digestive issues that don't seem to go away, seeing a natural health practitioner or functional medicine doctor is key to getting to the root of the issue. 

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