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Dietary Oxalates: Good or Bad? What’s the science behind it all

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Have you heard talk about dietary oxalates and wondered if you should avoid them?

Or maybe you’ve learned about kidney stone risk and you want to play it safe…

Here is the science and everything you need to know!

The Facts:

  • Those of us with IBD are at increased risk for development of kidney stones
  • 80% of kidney stones are calcium oxalate
  • Dietary oxalates are naturally found in fruits, vegetables, nuts & grains
  • Half of the oxalate found in the urine is produced by the body rather than absorbed by food
  • Oxalate is absorbed and broken down in the colon
  • Certain gut bacteria are involved in the breakdown of oxalate
  • Dehydration and diets high in animal protein and low in diversity (plants) increase the risk of stones

Dietary Oxalate Intake Isn’t the Same as Produced Oxalate

If you read only the first 3 bullet points – you might make the assumption that the intake of dietary oxalates in the diet will lead to the development of calcium oxalate stones.

This would be what we call logical fallacy – combining two ideas that seem to be true but actually aren’t!

This argument is often made on blogs and it often leads to unnecessary amounts of fear and restrictions.

Half of the oxalate found in urine is actually produced by the body rather than absorbed from food so low oxalate diets are not typically recommended anymore even for those with kidney stones (1, 2).

There are scenarios when urologists may recommend a low oxalate diet but this only for patients who have high levels of oxalate in their urine (3, 4).

What are the Risk Factors for Developing Calcium Oxalate Stones

One of the biggest risk factors for developing kidney stones is dehydration. We know those of us with IBD are at increased risk of dehydration due to surgeries, electrolyte and fluid loss and certain medications.

Another risk factor is dietary intake that is high in animal protein and low in diversity (plants).

Here are the Facts:

  • Animal proteins that are high in purines such as red meat and organ meat increase risk
  • Animal proteins + low diversity leads to a less favorable luminal (in the colon) pH
  • An unfavorable pH in the colon increases likelihood of the formation of kidney stones
  • Fibers help great more favorable luminal pH & supports the gut microbes that degrade oxalates 
  • Breakdown of dietary oxalates happens in the colon
  • Oxalabacter forminges breaks down oxalates, Bifidobacteria and Lactobacillus also help the process

If you are concerned about kidney stone development focus on staying hydrated and supporting your gut microbes!

Resources: gut bacteria & oxalates, high animal protein & risk