Acid-base balance affects dietary choice in cats.

The effect of acid-base status on self-selection of dietary protein was examined in three groups of adult male cats fed 20% soybean-protein and lactalbumin diets formulated to produce acidic, neutral or alkaline status. In two experiments, cats were offered a choice between the 20% protein diets or (1) the same diet with additional protein as casein (49% total crude protein) or (2) the same diet with added soybean-protein and lactalbumin (43% crude protein). Casein contained 0.63 mmol H+/g and caused all three groups to avoid the high casein diets by day 4. The high soybean-protein-lactalbumin diets did not contain added acid but would produce some extra acid upon catabolism of the sulfur-containing amino acids. Again, all three groups avoided the high protein diets by day 4. In a third choice trial, cats adapted to three low protein diets containing appropriate electrolytes to cause neutrality, acidemia or alkalemia, were offered a choice between: neutral vs. acidic; acidic vs. neutral or basic vs. acidic. The cats chose the neutral, neutral and basic diet respectively, restoring or maintaining acid-base homeostasis for each situation. The diets producing acidosis lowered serum sodium and potassium concentrations. We conclude that cats select appropriate diets in an attempt to maintain acid-base homeostasis.