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Gut Health: Oxalates - What are they and how they can affect you?

“What is food to one, is to others bitter poison”

-- Lucretius (96 BC – 55 BC)

Many may have never heard about oxalates – What are they? What does it matter? Is this another of those food fads that comes ever-so-regularly?

What are oxalates? What does that have to do with Gut Health?

Oxalates are a common food component – we all eat them – so why do some have issues with them? Some may not even know that oxalates are the cause of their problem. Basically, they are crystals and one of their features is that they have pointy sharp edges – like small razor blades! They are generally indigestible by humans and generally remain in the gut before being pooped out! A normal healthy gut will resist absorbing them – on the other hand, an unhealthy gut can absorb these razor sharp crystals and we can only guess what damage they can cause - imagine a razor sharp crystal floating in the body...

A healthy gut resists absorption of oxalates Conversely, a leaky gut can allow oxalates to enter the body. There are normal gut bacteria – Oxalobacter formigenes that can deal with oxalates – this bacteria loves oxalates – however due to antibiotics: the over use of antibiotics, antibiotics in commercial meat, etc. ….. leading to dysbiosis, many are missing this bacteria, so oxalates can become a problem. Conversely, other “bad” gut microbes, Candida and Clostridia, can make oxalates, so gut health is extremely important.

Another issue is with poor digestion. Bile salts are important for fat absorption, however if there is inadequate bile, the fat is not broken down to small particles. In the normal situation, oxalates in the gut bind with calcium, forming calcium oxalate and are eliminated through the bowel. If there is a lot of fat around, because of poor bile formation, then calcium binds to the fat, so the oxalate is more easily absorbed. How many people in today’s modern world have gut problems? How many have dysbiosis? How many have had their gall bladder removed?

Answer – a lot!

So, it is not just the foods we eat but another important issue is how our gut deals with these oxalates.

Once absorbed, the body must protect itself. Oxalates must either be excreted through the kidney or store them somewhere in the body. Oxalates are highly reactive and can bind with calcium, magnesium as well as iron and copper – they can influence our metabolism. Oxalates can affect mitochondrial function and can create inflammation. Now you can see the connection between Candida and Fatigue!

What symptoms are caused by oxalates?

Some of the specific conditions related to oxalates:-

  • Pain – virtually anywhere -- THIS IS ONE OF THE MAIN SYMPTOMS

  • Arthritis

  • Interstitial Cystitis

  • Fibromyalgia

  • Oxalate arthropathy – pseudo gout

  • Vulvodynia

  • Kidney stones and urinary pain – bladder/urethral irritation

Oxalates can:

  • disrupt mineral absorption

  • create oxidative stress

  • activate the immune system to trigger inflammation

  • interfere with mitochondrial function

  • damage cells and tissues

  • cause Histamine release

Before we go any further – just have a think about why oxalates do what they do – think about the body processes that can be affected. How many different disease processes can oxalates cause?

  • Think – oxidative stress, inflammation – think autoimmune disease

  • Think histamine release – think allergies

  • Think mitochondrial interference – think chronic fatigue.

  • Think deposition of razor sharp crystals in the muscles – think fibromyalgia.

  • Think kidney stones, think painful urination, think vulvodynia.

  • Think joint pains…..

Hopefully now you can see the role oxalates can play in chronic disease.

Once oxalates are in the body, the diseases, symptoms, condition depend on where the crystals are deposited – hence the large variety of presenting conditions.

If we try to excrete the oxalates through the kidney, this can lead to kidney stones – note that a large proportion of kidney stones are made of oxalate. If stones are not formed then other symptoms such as bladder pain, dysuria, vulvodynia/genital pain may develop.

If the oxalates are deposited in the tissues then a large variety of symptoms occur such as muscle aches and pains – often can be called Fibromyalgia, joint pains, pseudo gout, chronic fatigue, etc

Sources of Oxalates

There are basically 2 sources of oxalates – endogenous – from within or exogenous – from outside i.e. our diet and from some gut microbes: candida and clostridia.

Endogenous – It is increasingly being accepted that 80-90% of our oxalate is made from within. Our ability to produce oxalates do depend on our genetics, and on nutritional deficiencies. Vitamin B1 and B6 deficiency can cause the body to produce more oxalates, Vitamin A deficiency can cause the gut to absorb more oxalates. High doses of Vitamin C can increase oxalate production – though some do dispute this.

Exogenous – the food we eat and from microbes in our gut.

What foods contain oxalates?

We can divide oxalate foods into High, Medium and Low. There are lists on the internet that you can search. I will mainly concentrate on foods that are High in oxalates. The point is not to follow a no oxalate diet but to reduce the amount of oxalate in the diet, a low to medium oxalate diet.

Remove the high oxalate foods to start with: though this is best done with the supervision of an appropriate practitioner. Also, at the same time, we need to fix:

  1. the gut

  2. help bile production

  3. take extra calcium so that it can bind to the oxalate – the best form is Calcium Citrate.

If you suddenly go onto a low oxalate diet, then a possibility of “dumping” may occur. Dumping is where the stored oxalates in the body suddenly get dumped because of the sudden change to a low oxalate diet. Oxalates come out of the body and can exacerbate any of the symptoms you are experiencing, or suddenly get other symptoms such as joint pains, painful urination, excess urination or even bed wetting, burning sensation with bowel movements, sandy poop, skin rashes, brain fog, eye pain, insomnia, anxiety/depression.

Foods high in oxalate include:

  • Beans

  • Beer

  • Beets

  • Berries

  • Chocolate

  • Coffee

  • Cranberries

  • Dark green vegetables, such as spinach

  • Nuts

  • Oranges

  • Rhubarb

  • Soda (cola)

  • Soy beans

  • Soy milk

  • Sweet potatoes

  • Tea (black)

  • Tofu

  • Wheat bran

Start by eliminating foods on the above list. Don’t get confused, some of the lists on the internet may be different – don’t let it bother you too much. Stick to the main principle. Eliminate high oxalate sources and eat mainly from the medium and low list. The list of low to medium oxalate foods are quite large so I suggest you visit the following websites. You may notice that the low oxalate diet is combined with a low Histamine diet… As mentioned above, oxalates can cause a Histamine release – therefore it would be a good idea to combine a low histamine diet with the medium to low oxalate diet.

Just a word of warning - if you have recently gone on a spinach smoothie diet thinking it is healthy – perhaps for you it may not be a good thing!


Start just by eliminating the high oxalate foods, continue eating low to medium oxalate foods….. but at the same time start to improve your body’s ability to cope with oxalates:- 1/ fixing the gut, 2/ improve liver and gall bladder function, 3/ improve nutrition, 4/ deal with any other relevant conditions.


Marangella M, Fruttero B, Bruno M, Linari F. Hyperoxaluria in idiopathic calcium stone disease: further evidence of intestinal hyperabsorption of oxalate. Clin Sci (Lond.).1982;63(4):381-5.

Berg W, Haerting R, Bothor C, Meinig S, Eschholz A, Schulze HP. [Diagnosis of intestinal oxalate hyperabsorption in patients with idiopathic recurrent calcium oxalate urinary calculi]. Urologe A. 1990;29(3):148-51.

Kaufman DW, Kelly JP, Curhan GC, et al. Oxalobacter formigenes may reduce the risk of calcium oxalate kidney stones. J Am Soc Nephrol. 2008;19 (6):1197-203.

Dobbins JW, Binder HJ. Importance of the colon in enteric hyperoxaluria. N Engl J Med. 1977 Feb 10;296(6):298-301.

Harlow BL, Abenhaim HA, Vitonis AF, Harnack L. Influence of dietary oxalates on the risk of adult-onset vulvodynia.

J Reprod Med. 2008 Mar;53(3):171-8.

Allison, MJ, Cook, HM, Milne, DB, Gallagher, S, Clayman, RV. Oxalate degradation by gastrointestinal bacteria from humans. J Nutr. 1986;116:455–460.

Oxalates & Chronic Disease: How the healthy foods you love may be making you sick

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