Does low ash cat food, or your cat's diet in general, impact the formation of struvite crystals? What about oxalate crystals? Here's a look at the significance of ash in the food.
We'll look at what ash is, why it's in the food, and how it might impact your cat's health. We'll also talk a little bit about feline lower urinary tract disorder (FLUTD), formerly labeled FUS or feline urologic syndrome.
FLUTD covers a number of feline urinary tract problems, including bladder stones, cystitis, the formation of crystals in the urine, and bacterial infections.
If your cat has FLUTD, your vet may suggest a change in diet in order to help combat it.
If your cat has crystals or stones in the urine, this can become a serious condition.
If urinary blockage occurs (common in males), this is a life threatening condition and needs immediate treatment.
See this CFA article on feline bladder stones and urinary obstructions for more detail.
What is ash, and why is it in cat food?
There's an article by Holly Nash, DVM, MS, from the Veterinary Services Department, Drs. Foster & Smith, Inc. that explains this in detail: Reducing Struvite & Calcium Oxalate in the Urine of Cats
She tells us ash is essentially the minerals that remain after burning a food sample at 600 degrees C for two hours. It contains essential minerals, including calcium, phosphorous, potassium, sodium, manganese, magnesium, and trace minerals.
These minerals are required in a cats diet. So, in this respect, ash is a good thing.
You'll often see references to low ash cat food. It was once thought that low ash cat food would help reduce or prevent urinary crystals, but the thinking has now changed.
It's now thought that the main factors in the development of struvite crystals in cats are urine pH, magnesium concentration, and the cat's water consumption (it's said that most cats don't drink enough). Oxalate crystals may form when cats are fed diets that are low in magnesium, and their urine is acidic.
In addition, although magnesium has been linked to the formation of struvite crystals, low ash does not always mean low magnesium.
Dr. Nash also writes in the above article that the type of magnesium in the food is key as well:
"The difference appears to be that magnesium oxide causes alkaline urine, and magnesium chloride results in the formation of acidic urine."
The FDA does not allow a low ash claim to be put on the cat food label. But companies will still sometimes declare their product as low ash in their literature.
Dr. Nash also tells us that cats who have a tendency to develop struvite crystals or stones should be fed free choice, rather than at specific meal times. Apparently, after a large meal, the pH of the urine tends to become alkaline. Eating smaller meals will keep the urine more acidic.
So, eating a dry cat food throughout the day would be better than two meals a day of a wet cat food. There are also some diets that are specially formulated to reduce struvite crystals.
Ironically, calcium oxalate crystals may form in some cats if the pH is too acidic. And, also ironically, those cats with interstitial cystitis (IC) may do better on a wet cat food.
This page on IC Diet Management from The Ohio State University College of Veterinary Medicine talks about the benefits of canned foods over dry for IC, and includes good options for a procedure on how to switch cat foods.
Instead of looking for low ash cat food (an outdated concept), some cat owners have reported success with reducing urinary problems, including crystals, by switching to a natural or organic wet food.
I've also heard that diets specifically designed for urinary tract problems can help (talk to your vet about these). Other cat owners swear by raw food diets for a host of ailments, but some vets are not big on this idea.
If your cat has urinary tract problems, you'll have to work with your vet to find the right balance of the right diet, level of exercise, and water consumption for your cat.