What are Oxalates and Should I Be Worried about Eating Greens?

Young spinach in a wooden plate

Oxalates or Oxalic Acid. Have you heard of them and are you concerned by them? There is a lot of confusion over what oxalates are and so I wanted to write this blog post to clarify a few things that I have read recently that are not true. Please note that Oxalates and Oxalic Acid are the same thing and so this post refers to oxalates.

In summary: Please don’t stop eating your raw greens or smoothies; Let me explain why.

What are Oxalates?

Oxalates are naturally occurring compounds found in foods. They also occur naturally in the body and can also be formed as a by-product during the process of Vitamin C metabolism.

What contains Oxalates?

There are many different food sources that contain oxalates. Oxalates are found in higher concentrations in plant based foods but are also found in animal products too. One of the first foods that everyone associates with oxalates is raw leafy greens. Oxalates are especially high in spinach but not as high in kale.  In fact there are more oxalates found in chocolate (especially dark chocolate) and cashews than in kale! They are also found in legumes, buckwheat, rhubarb, parsley, sweet potatoes and start fruit (as well as many other foods). The root and leaves of rhubarb contain dangerously high concentrations of oxalates and should not be consumed raw. Growing conditions and time of harvest can also affect the amount of oxalates a food contains.

Even if we did not eat any foods containing them (which would be quite hard to do), our bodies can still make them through a variety of natural processes.

Should I be concerned about Oxalates?

Oxalates can be a problem for example if you are prone to kidney stones, gall stones, have poor gut health or a history of recent or intense antibiotic use.

The main concern that everyone has and the scaremongering that has been reported is that they can potentially cause kidney stones. The majority of kidney stones that form (over 80%) are composed of calcium oxalate whereby oxalates bind with minerals such as calcium and form calcium oxalate. They normally pass through the urine with no concerns. However in people susceptible to kidney stones they can crystallise and form stones.

Oxalates can also affect the absorption of calcium as they bind with them and make them less usable. Foods such as spinach and kale therefore do not have as much bio-available calcium because it is bound with oxalic acid.

What can you do if you have any concerns about Oxalates?

If you are concerned about the amount of oxalates that you are consuming you can do the following:

  • Rotate raw greens with cooked greens however be aware that cooking your greens only reduces the oxalate content by 5-15% 
  • Drink lots of water
  • Ensure you are getting enough calcium in your diet from a variety of different sources (see this post for plant based sources)
  • Do not consume too much vitamin C (As oxalates can be a by-product of vitamin C metabolism)
  • Rotate your greens so you are not always eating spinach (especially in smoothies)
  • Limit your greens intake if you are susceptible to kidney stones
  • Limit the juicing of greens if you are susceptible to kidney stones as you are removing the fibre and therefore have increased concentrations of oxalates
  • Avoid high oxalate foods if you have any kidney issues, gout or rheumatoid arthritis

Remember, everything in moderation and don’t stop eating those greens!

As always, if you have any medical conditions, consult with a doctor or nutritionist before changing your diet.

4 thoughts on “What are Oxalates and Should I Be Worried about Eating Greens?”

  1. Thanks Melanie.
    This clears up a lot of things for me. When I drink green smoothies it’s often because I want something quick to prepare. Ive been told to blanch the greens before using them in smoothies, but then that negates the time savings.
    I think I’ll just be more diligent in rotating my greens.

  2. Charles McNaughton

    Thanks for the information Melanie I do consume a great deal of greens and will have to mix it it up a bit more will catch up with you Wednesday

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