Dog owners are afraid of oxalates for no real, scientific reason other than what they have read on the internet. In this article, I will go over:
- Oxalates in the body
- Oxalates in food
- Why are we scared of oxalates?
- The women who was linked to acute kidney injury because of her green drinks
- Nutritional sources of oxalates
- What dogs should not be fed oxalates?
- The importance of hydration
- The importance of making sure your dog pees
- What about inflammation?
- Oxalate stones associated with kibble
- How to feed food with oxalates
- Where does that leave us
Oxalates In The Body
Cells have oxalates, albeit in lower concentrations compared to other molecules like glucose or amino acids. They are produced as a normal byproduct of various metabolic pathways within the body.
- Oxalates are mainly produced in the liver through the metabolism of glyoxylate, a molecule derived from carbohydrates, fats, and certain amino acids. The pathway is: Glyoxylate -> Glycolate -> Oxalate
- In addition to the liver, smaller amounts of oxalates may also be produced in other tissues in the dog’s body, such as the kidneys and brain. However, the liver remains the primary source of oxalate production.
- The exact function of oxalates within our dog’s cells is still under investigation.
- Some potential roles include:
- Contributing to energy production in the mitochondria.
- Regulating cell signaling pathways.
- Detoxifying harmful substances.
- Most oxalates are excreted from the body in the urine.
- A small amount is also eliminated through feces.
Oxalates in Food
Oxalates are naturally occurring organic molecules found in many plants.
It is also associated with animal protein. While the meat doesn’t directly contain oxalates, feeding animal protein can indirectly influence oxalate levels in the body. This happens through several mechanisms:
Increased endogenous oxalate production:
- Animal protein is metabolized into amino acids, some of which can be converted into glycolate in the body. Glycolate is a precursor to oxalate, so increased protein intake can lead to higher oxalate production.
Why Are We Scared of Oxalates?
Oxalates have been primarily been associated with the formation of urinary stones as well as associated with Kidney Disease in humans but when you dig into the research, this isn’t a real concern for most humans and has not been studied in dogs to the extent that we have prescriptive ways in how to handle things like kale and chard.
The Women Who Was Linked To Acute Kidney Failure Because Of Her Green Drinks
There was a report of a case of acute oxalate nephropathy in a 65-year-old woman, temporally associated with the consumption of an oxalate-rich green smoothie juice “cleanse” prepared from juicing oxalate-rich green leafy vegetables and fruits. Predisposing factors included a remote history of gastric bypass and recent prolonged antibiotic therapy. She had normal kidney function before using the cleanse and developed acute kidney injury that progressed to end-stage renal disease. Consumption of such juice cleanses increases oxalate absorption, causing hyperoxaluria and acute oxalate nephropathy in patients with predisposing risk factors.
The media took this case report and ran stories about the dangers of juicing.
It’s unfortunate she passed. And what we need to remember is:
- She was in late-stage kidney failure
- She had gastric bypass surgery
- She had a history of diabetes
- She was juicing over a kilogram of vegetables
- The antibiotics she was taking were a known kidney-toxic drug
It’s interesting to me that the media linked her smoothies to her death but made no mention of her medical history or the antibiotics she was taking.
This is not a standalone case report. It is further reported that other predisposing factors for AKI, such as dehydration, CKD, diabetes and gastric bypass surgery come into play.
This is why tracking down the sources, reading the case reports, trials, studies, and reviews are so important. Basically – learn how to go beyond click-bait and blog articles that regurgitate information without reading the resources.
Oxalates on its own, are not bad. It’s that “excess oxalate has deleterious effects on kidney function”.
Nutritional Sources of Oxalates
- Leafy greens: Spinach, rhubarb, Swiss chard, beet greens, collard greens, kale
- Vegetables: Beets, sweet potatoes, okra, potatoes
- Fruits: Berries, figs, kiwi fruit, oranges
- Legumes: Dried beans, lentils
- Grains: Wheat bran
What Dogs Should Not Be Fed Oxalates
- Dogs with a history of stone formation (ask vet to verify if the stones contain calcium oxalate and at what concentration – less than 20% is marginal)
- Dogs with kidney damage
- Certain breeds like the Coton de Tulear breed which can have the inherited disease – Primary Hyperoxaluria
Remember it’s excess levels of oxalates that we should be watching in humans and dogs and I don’t think any of us are juicing bundles of kale for our dogs.
Most of the dogs that are having kale or chard added to their bowls are doing it at less than 15% of the bowl.
The Importance of Hydration
Let’s not forget that the kidneys are responsible for filtration. And before we blame oxalates we should mention how important hydration is.
The Importance Of Making Your Dog Pee
It’s really important to bring your dog out to go pee. Don’t get lazy because if they don’t have a chance to empty their bladder bacteria can build up.
Having a habit that they know is key no matter if it’s raining, hot, or snowing and no matter what time of the morning, day, or night it is.
If your dog gets fed kale once a week, but doesn’t drink enough water, and only goes out to pee three or four times a day and gets stones, it’s probably not the kale in the diet that caused the stones.
Let’s Not Forget Calcium
Oxalates have an affinity to calcium and one of the reason that oxalates are labeled an “antinutrient” is because it binds to calcium.
We have to also know the context. Most, if not almost all of the hype and articles online are related to humans. And humans…. for the most part… do not consume enough calcium.
Most humans do not even know how much calcium they are supposed to take each day.
So when they have low calcium intake, and high oxalate intake, we see problems.
But when we see moderate to high calcium intake, and high oxalate intake, not as many problems.
This is because the amount of calcium intake strongly influences intestinal absorption of oxalate.
Our dogs on the other hand, for those that are fed kibble, are getting their daily amount of calcium and if you’re formulating their diets, it’s most likely your dogs are getting enough calcium. Diet calcium lowers urine oxalate.
What About Inflammation?
Oftentimes we worry about things like kale or chard in a dog’s diet when we should be worrying about keeping inflammation low first.
Oxalate Stones Associated With Kibble
In a 2012 review of peer-reviewed scientific reports:
- Out of the 40,612 canine and 11,174 feline uroliths evaluated, 41% of the dogs had calcium oxalate stones. The associated kibble diets are a likely cause.
- Neutered male dogs are at greater risk than those that are sexually intact. There are also breed-based predispositions towards the development of calcium oxalate stones. In dogs, many of the commonly affected breeds are small, including the miniature schnauzer, Lhasa apso, Yorkshire terrier, bichon frise, and miniature poodle. Although all small in stature they are not closely genetically related, originating from different evolutionary clusters. Keeshonds (a larger breed) have also been found to be over-represented among calcium oxalate stone-forming dogs, which is probably due to this breed’s known predisposition to the development of primary hyperparathyroidism
In a 2018 study of 10,444 uroliths, diet was not even looked at.
In neither case were dietary intake of oxalates mentioned.
Dietary Intake of Oxalates In Dogs Not Yet Studied
Unfortunately, dietary intake of oxalates have not yet been studied in dogs.
How To Feed Oxalates
I find it silly to say that. I think it should read, what vegetables can we feed our dogs. But I know that’s not what you’re thinking.
In any event, oxalates are water soluble so if you steam or cook them in a little water, that will reduce the oxalates (if you’re worried about it). You can discard the water and add the vegetables to your dog’s bowl.
I tend to focus on one above vegetable at a time in the bowl. And that portion can be anywhere from 8 to 15% for most diets.
We’re still in the phase of “feed a dog a low-protein diet” to avoid stones. And so that is why we must look at what research has been done in the human space as it relates to this area.
Where Does That Leave Us?
If you’ve made it this far the key takeaways are:
- Excess consumption of oxalates should be watched when there is a health reason to do so
- Certain breeds are linked to higher cases of stone formation
- Hydration is extremely important
- Dietary intake of oxalate foods has not been studied in dogs at the same level as in humans
In a nutshell, if you’re adding less than 8% of oxalate-rich foods and rotating all the different ingredients then I don’t think you have anything to be overly concerned about.
Hannah Zulueta obtained her Certificate in Canine Nutrition from CASI Institute. She is also studying for her Doctorate in Acupuncture, Traditional Chinese Medicine, and Herbalism from the esteemed Pacific College of Health and Medicine.
She resides in San Diego with her three dogs, Maggie, Orbit, and Mr. Higgins.