Hyperthyroidism is unfortunately common in older cats – and many believe that it is linked to the foods they eat. In fact, some studies have linked certain feline commercial diets directly to this disease.

A common diet traditional veterinarians recommend for a hyperthyroid cat is a prescription canned diet by Hill’s (y/d). And, while it appears to be effective in the interim, we would not recommend this diet for long term use. The ingredients aren’t appropriate for an obligate carnivore and can cause other health problems over time. We also recommend to always avoid any dry prescription diets.

In reality, no dry food should be fed to cats – especially those with this disease. The high amount of carbohydrates in kibble is detrimental to a kitty’s health, causing all sorts of disease.

Questions remain about what exactly to feed a hyperthyroid cat – though we do have a suggestion below. That said, because of the research I’ve done, I’d like to discuss what not to feed cats with hyperthyroidism.

Foods Not To Feed Cats With Hyperthyroidism

Avoid fish flavored foods. Toxins (called PBDEs) in cat foods containing fish have been researched – and the results were astounding. The study states:

“The present study suggests that pet cats are exposed to MeO-PBDEs through cat food products containing fish flavors and that the OH-PBDEs in cat blood are derived from the CYP-dependent demethylation of naturally occurring MeO-PBDE congeners, not from the hydroxylation of PBDEs.¹

Dr. Jean Hofve, DVM. further explains this issue of PBDEs in fish flavored cat foods:

“There is a link between the feeding of fish-based cat foods and the development of hyperthyroidism, which is now at epidemic levels… Fish-based foods are even worse, because marine organisms produce PDBEs naturally and can bioaccumulate up the food chain to high levels in fish; this compounds the exposure cats get from fabrics and dust.”² 

What does all this mean in plain English? Basically – there are toxins in fish flavored cat foods that are contributing to the epidemic of feline hyperthyroidism. Avoid them at all costs.

Steer clear of foods with soy. Pet food companies commonly use soy as a filler ingredient for protein. It’s a cheap replacement and damaging to our cats’ health. Although considered protein, soy acts as a carbohydrate in our cats’ bodies and has a direct link to thyroid damage.

If you have a kitty with hyperthyroidism, we recommend contacting Fetching Foods and speaking with them about custom formulating a low iodine, fish & soy free food for your sweet babe.


Recommended Support For Feline Hyperthyroidism


CATalyst Antioxidant Enzyme Formula – 2 oz



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