Would cat foods made with ingredients like fish, that may be high in magnesium, predispose my cat to urinary tract infections?
Presuming the diet containing the fish is properly balanced then neither the fish nor the magnesium should themselves lead to urinary tract disease. Early work indicated that diets high in minerals (ash) were associated with urinary tract issues. Some diets were also supplemented with magnesium salts like magnesium oxide and magnesium sulfate in order to meet the cats’ magnesium requirements. Diets of this type were associated with a predisposition for urinary tract disease (i.e. struvite urolithiasis). Magnesium salts can have an alkalinizing effect on the urine (increases pH above neutral). However, it was shown that the anion (oxide, chloride) rather than magnesium itself was to blame for the rise in urine pH (Buffington et al., 1985). Magnesium from fish and animals is primarily in the ionic form or as a hydroxide in bone.
