What is Oxalate?

by Heidi on March 7, 2012

If you are new to the low oxalate diet, you may be wondering “What is oxalate?”  All oxalate starts out as oxalic acid–a naturally-occurring strong acid that dissociates (ionizes) completely in water1.  This complete dissociation allows oxalic acid to form strong bonds with many minerals, including calcium, iron, magnesium, potassium and sodium2.  When oxalic acid binds with these minerals, it forms a salt which is then referred to as calcium oxalate, magnesium oxalate etc.  If the salt easily dissolves in water (like table salt) it is called soluble oxalate.  If it does not dissolve, but remains in a crystalline form, it is called insoluble oxalate2.

Calcium Oxalate Crystals

Calcium Oxalate Crystals

Both soluble and insoluble oxalate are commonly found in plants and to a much lesser extent in animals, including humans3. Although scientists aren’t sure why some plants contain a lot of oxalate, they have discovered that oxalate  plays many roles in the plant’s ecology and biology.

Oxalate May Be Important For:

1.) Protecting the plant from insects and other foraging animals.  For example, oxalate can cause burning, irritation, and stinging sensations in the mouths or skin of animals that eat it1,4,5

2.) Calcium regulation.  For example, a plant might make more oxalate when intercellular calcium levels are too high so that the oxalate can bind with the calcium 1,4,5

3.) Heavy metal detoxification.  For example, oxalate may bind with aluminum and help remove it from the plant1,4,5

4.) Tissue support.  For example, calcium oxalate is often found in the cell wall of a plant–the structure that supports a plant and gives it shape (like bones support and give shape to many animals) 1,4

5.) Ion balance1,4

Oxalic acid is formed as part of the plants’ normal metabolic processes using numerous different biosynthesis pathways3,5 (we will explore a few of these in later articles).  Researchers used to believe that oxalate was only a by-product in metabolism, but we now know that biosynthesis of oxalate is a carefully regulated process and that a plant can synthesize different sizes and shapes of calcium oxalate crystals depending on what function the oxalate will perform for the plant5.   People also synthesize oxalate as part of our normal metabolic processes using the same biosynthesis pathways as plants(In people, we call this endogenous oxalate production).  Most people and animals make negligible amounts of oxalate, but a few synthesize a lot, usually as the result of a genetic condition called primary hyperoxaluria (types I, II, or III) or because of a vitamin deficiency (often Vitamin B6 or thiamine).

Was this article helpful?  What other types of articles would you enjoy seeing on Low Oxalate Info?  Please let me know in the comments section below.


1.)  Libert, Bo, and Vincent R. Franceschi. 1987. Oxalate in crop plants. Journal Agriculture and Food Chemisty 35(6):926–938.

2.)  Savage, G. P., L. Vanhanen, S. M. Mason and A. B. Ross. 2000. Effect of cooking on the soluble and insoluble oxalate content of some New Zealand foods. Journal of Food Composition and Analysis 13:201-206.

3.)  Franceschi, V.R., and H.T. Horner Jr. 1980. Calcium oxalate crystals in plants. The Botanical Review 361–427.

4.)  Rahman, M. and O. Kawamura. 2011.  Oxalate Accumulation in Forage Plants: Some Agronomic, Climatic and Genetic Aspects. Asian-Aust. Journal of Animal Science. 24(3): 439 – 448.

5.) Franceschi, V.R., and P.A. Nakata. 2005. Calcium oxalate in plants: formation and function. Annual Review of Plant Biology 56:41–71.


{ 9 comments… read them below or add one }

Michelle March 8, 2012 at 12:39 am

Great article! Isn’t that just an amazingly popular picture of oxalate crystals (I used it here: http://lowoxalatedieting.com/the-low-oxalate-diet-it-isnt-easy/) LOL. Gotta love Wikimedia Commons! :)

Your approach to the subject is far less biased than mine…I tend to always view it through the lens of the evils it commits within the human body, rather than the useful role it undoubtedly plays for the plants which produce it. Thanks for presenting a bit of the other side of the coin!


Heidi March 8, 2012 at 4:21 am

Thanks, Michelle. I will get to the evils it commits within the human body soon! Isn’t that picture beautiful? I found another one that I want to frame and put up in my house. It’s amazing that something so beautiful can cause so much harm.


Karla March 8, 2012 at 3:35 am

This is fantastic. You’ve made it very easy to understand!


Heidi March 8, 2012 at 4:22 am

Thanks, Karla! That means a lot coming from you.


Beth March 8, 2012 at 5:18 am

I am so glad to find your site! Thank you!
Do you know what part genetics plays in all this? If I have had issues with high oxalate foods (which I do, so following a low oxalate diet now) are my children also genetically predisposed to such problems?


Heidi March 9, 2012 at 7:43 am

I plan to do some posts about the genetic link later after I do some more research myself, but like most diseases it seems that there is a genetic connection. The VP Foundation newsletters and the Trying Oxalates Yahoo Group is full of anecdotal stories of people with oxalate-related symptoms who have family members with oxalate-related symptoms. What really surprises me is the number of parents who have multiple children with oxalate-related symptoms, who didn’t realize they also could benefit from a low oxalate diet until they went on one by default with their children and realized that some old injury got better or some unexplained bladder pain cleared up. Of course, this doesn’t mean that just because you have a problem that your children will, too. I think like with most disease, both a genetic predisposition and an environmental trigger must be present. Your kids may not have inherited the predisposition and if they did, they may never have a severe enough environmental trigger to cause disease. That’s my hope for my own children who so far seem to be doing very well on a medium oxalate diet.


Beth March 9, 2012 at 11:03 am

Thank you, this is helpful for me to consider.
Any evidence (that you know of thus far in your research) of particular environmental triggers that affect oxalates? We live in an area where I probably need to really take this into consideration (high air pollution being just one of those environmental issues).


Heidi March 10, 2012 at 7:29 am

Two environmental triggers that seem to be quite common are gluten and certain antibiotics. Both can contribute to high oxalate levels in the blood (and eventual oxalate-related symptoms) by impairing gut function.


Dario Dinatale April 6, 2012 at 12:04 pm

Regards for all your efforts that you have put in this. Very interesting information. “One cool judgment is worth a dozen hasty councils. The thing to do is to supply light and not heat.” by Woodrow Wilson.


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