Sodium and chloride are essential electrolytes involved in maintaining fluid balance, blood volume, nerve and muscle function, digestion, and normal acid-base balance. In a natural prey diet, sodium is supplied throughout the animal’s tissues and body fluids, particularly its blood. Retail cuts of meat contain very little blood, so a homemade diet based primarily on retail cuts of meat does not provide the sodium a cat would obtain from eating whole prey.

Sodium chloride was added to the TCfeline formulas after nutritional comparison showed that the prepared food fell below AAFCO and NRC sodium recommendations and the levels naturally present in whole prey. Inadequate sodium intake is not trivial. Research in growing kittens has shown that sodium deficiency cause several signs of dehydration, loss of appetite and impaired growth. Sodium deficiency activates the  renin–angiotensin–aldosterone system (RAAS), part of the body’s hormonal response for conserving sodium and maintaining fluid balance and blood pressure. Sodium also contributes to maintaining the mildly acidic urine desirable in cats.

Interestingly, cats do not appear to compensate for insufficient sodium by seeking out salt. Studies have found no innate preference for salt in kittens, even when they were sodium-depleted. This makes biological sense for an animal whose ancestral diet normally supplied sodium with every meal: unlike many herbivores and omnivores, a prey-eating carnivore would have little need to search for a separate source of salt.

TCfeline therefore includes a carefully measured amount of sodium chloride to replace sodium and chloride that would naturally accompany whole prey but are inadequately supplied by the retail meats used to prepare homemade cat food. The inclusion of salt in TCfeline serves to restore levels of essential electrolytes. Its purpose is not to make the food more palatable. In fact, the prepared cat food will not have a detectable salty taste.