Urinary Tract Disease
By: Dr. Linda East
South Penn Cat Clinic
For the past twenty years, the high incidence of urinary tract disease has led to considerable research, but the condition still exists.
Research first showed that the sandy substance and stones that formed in the bladder were made up of ammonia, magnesium and phosphorus, called "struvite." Magnesium and phosphorus are components of "ash," which is really just minerals, so named because if you take foods and burn them up, what is left is "ash" which does not burn. Calcium and all other dietary minerals are also "ash" and are required for a complete diet. So "ash" is not bad, but for a while the theory was that there was too much of it in cat food. Ash was reduced, but the problem continued.
Research at Cornell University showed that perhaps it was the magnesium component of ash that was the culprit. As a result many manufacturers began to formulate cat food with low magnesium. However, a few years later a surprising paper showed that when cats were fed magnesium as an alkaline salt, an alkaline urine was created and stones were found (as was shown in the Cornell study). But if fed magnesium as an acid salt, thus acidifying the urine, stones did not form. So it was not the ash or the magnesium at all, but whether or not the urine was acidified or alkalized.
Manufacturers began adding acidifiers, resulting in a dramatic decrease in cats with struvite stones. The story does not end here, however. As the percentage of struvite stones decreased, the percentage of another type of stone, calcium oxalate, has increased. Calcium oxalate forms in an acidic urine. In humans, increasing magnesium intake appears to decrease the probability of oxalate stone formation. There are also other health problems associated with decreased magnesium.
An ideal nutritional approach using commercial cat foods to prevent both types of stones does not exist. The answer lies, as always, in striving toward the natural diet and in maintaining overall health and resistance to disease.