Tuna-only diet not sufficient for cats

Q: My elderly cat Tater Tot is losing his appetite for dry cat food, but he loves the tuna I eat. Now that he's eating only tuna, I guess I should ask if that's okay for him.

A: It seems you have two concerns: Tater Tot's recent disinterest in dry food and his all-tuna diet.

I'm suspicious that Tater Tot may be experiencing mouth pain that makes crunching dry food uncomfortable, so I suggest he see his veterinarian as soon as possible.

I also am concerned that he is eating only tuna, because this diet is nutritionally incomplete and unbalanced. Tuna is low in vitamin E, so Tater Tot could develop [steatitis (stee-ah-TITE'-is), a painful and sometimes fatal inflammation of the body's fat. In addition, tuna's low vitamin K levels can cause internal bleeding.

Cats require large quantities of B vitamins, but tuna provides only tiny amounts. These deficiencies, combined with possible mercury contamination, can cause muscle weakness, loss of coordination, tremors, seizures and other neurologic problems. Tuna is low in calcium, too.

Tuna also contains inadequate linoleic acid, an essential fatty acid that promotes healthy skin. Tuna that is beginning to spoil releases histamine, which can cause skin itchiness and redness. Conversely, tuna is high in magnesium, which may contribute to feline bladder problems. Moreover, cats fed canned tuna have an increased risk of oral squamous cell carcinoma.

So, schedule an appointment with your veterinarian to figure out why Tater Tot refuses his regular dry food. Until then, feed him canned cat food that's nutritionally complete and balanced, and save the tuna for yourself.

Lee Pickett, V.M.D. practices companion animal medicine in North Carolina. Contact her at vet@askthevet.pet.