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Siamese cat eating tuna from a dish

Too much tuna bad for cats

Q: My 13-year-old cat, Luna, lost her appetite for dry cat food, but she’ll eat the canned tuna I eat. Is it okay for her to eat only tuna?

A: No. Luna should see her veterinarian to determine why she refuses dry food. For instance, she might have a diseased tooth causing pain that needs treatment.

Luna may eat a balanced canned cat food or a small amount of canned tuna, but not straight tuna. An all-tuna diet has deficiencies and excesses that can cause serious medical problems.

For example, tuna doesn’t provide enough vitamin E, so Luna can develop pansteatitis, a painful, debilitating and sometimes fatal inflammation of the body’s fat. The insufficient vitamin K in tuna causes internal bleeding which has killed some cats.

Neurologic problems, such as seizures, tremors, loss of coordination and muscle weakness, are common in cats that eat only tuna. These problems occur with mercury contamination of tuna and because canned tuna contains only tiny amounts of B vitamins, which cats require in large quantities.

Skin problems occur because tuna is deficient in an essential fatty acid called linoleic acid. Tuna that is beginning to spoil releases histamine, which can cause skin itchiness and redness. Tuna also is low in calcium.

Conversely, tuna is high in magnesium, which may contribute to feline bladder problems. Also, cats fed canned tuna have an increased risk of oral squamous cell carcinoma.

So, feed Luna a balanced canned cat food, and have her veterinarian determine why she’s refusing dry food.


Lee Pickett, V.M.D. practices companion animal medicine in Pennsylvania. Contact her at askdrlee@insurefigo.com

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