There was a time when, if a cat had chronic urinary tract issues, a change in diet was recommended. Vets often advised switching to cat foods containing lower levels of ash because they believed ash contributed to urinary crystals. Now we know it's less about ash, more about urine pH.
Ash, Not Ashes
If you are worried that Mittens is eating cinders in her food, don't fret. When commercial cat food is processed, ash is the inorganic mineral content that's left after the organic portion of the food has been cooked off. The mineral content in ash can be calcium, phosphorus, magnesium, sodium, potassium, sulfur and silicon in any combination, as well as other trace minerals. When the food is heated to around 550 to 600 degrees, the inorganic leftovers comprise the ash content.
Ash in Cat Food
If Mittens had been around and suffering from urinary tract issues in the 1970s or '80s, you would have been advised to feed her a food with lower ash content -- likely a prescription food. At the time, conventional wisdom was that ash caused, or contributed to, crystals in cat urine. There was a relationship between a high-ash diet and the occurrence of urinary tract obstructions -- called struvite -- so vets believed the high ash level caused the struvite. However, research since then has shown that it's not the ash causing urinary tract obstructions; Mittens' urine pH is the important factor.
Commercial pet foods did aggravate urinary conditions for some cats because the food created a more alkaline urine for the cats. The higher alkaline level contributed to the increased struvite. Many commercial cat foods have a high vegetable and grain content, creating a more alkaline urine. Diets with more meat create a more acidic urine, which is beneficial for Mittens' urinary tract.
It's More Than Diet
Most cats with urinary tract disorders are idiopathic, meaning there's no identifiable cause. Idiopathic cases don't have stones, tumors, cancer or infections and generally clear up on their own in about a week. If this is the case with Mittens, it's still a good idea for her to see a vet so she can have a little relief, perhaps with the help of anti-inflammatories or other medication. Diet is important to maintaining good urinary health and minimizing the occurrence of crystals in cats who are predisposed to them. However, it's not as much about feeding a diet low in ash, magnesium or other minerals, but more about ensuring Mittens eats so she'll maintain a proper urine pH. A high-protein diet will help meet this goal. Canned food and ensuring Mittens drinks plenty of water will also minimize the chance of crystal formation.
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