y/d – A New Diet for Cats with Thyroid Disorders

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October 2011

By Jeff Grognet, DVM, BSc(Agr) & Louise Janes, BSc(Agr), DVM

A new diet came out last month in the US and it’s just a matter of time before it comes to Canada. It is designed for cats with hyperthyroidism. The idea is that it is deficient in iodine so this prevents the production of thyroid hormone by the tumour. This is a site that describes the tumour and current treatment.

http://www.fabcats.org/owners/hyperthyroidism/info.html

Here is the link on the launch of the diet.

http://vetmedicine.about.com/od/diseasesconditionscat/a/Feline-Hyperthyroidism-Hills-Y-D-Diet.htm

From this article, it would seem to be a great idea. However, we’ve got a lot of concerns and this is why we are not recommending it.

1. y/d has a significant amount of calories from carbohydrate and it’s low in protein which is not appropriate for a cat. (more on this when we look at the ingredients).
2. We do not know what the true iodine requirement is for cats, so how can we create a diet that is iodine-deficient?
3. We don’t know how the thyroid gland responds to low iodine (no biopsies or appropriate blood tests were done on the cats studied on the diet.)
4. More importantly, how does the body respond to an iodine deficient diet?
5. Hill’s suggests that the diet “restores thyroid health”. It does not remove the growth in the thyroid gland so what does this mean?
6. But, the worst thing of all is the ingredients. This diet is made of corn. Here’s the list: Corn Gluten Meal, Animal Fat (preserved with mixed tocopherols and citric acid), Whole Grain Corn, Soybean Mill Run, Dried Egg Product, L-Lysine, Chicken Liver Flavor, plus vitamins and minerals

At our hospital, we have continually been suggesting high MEAT/low carbohydrate (CARB) diets for our feline patients. This just makes sense—cats are carnivores.

One of the worst foods on the market is one called Purina product Mainstay. You can find it on the bottom shelf at grocery stores. For fun, grab a bag and read the ingredients in the dry cat food. There is no meat in it. We call it “sawdust for cats.”

Here’s the ingredient list of a marginally better food, Purina Cat Chow:

Poultry by-product meal, ground yellow corn, wheat flour, corn gluten meal, soybean meal, brewers rice, beef tallow preserved with mixed-tocopherols (source of vitamin E), fish meal, brewers dried yeast, animal digest,plud vitamins and minerals

If you were to put the grains (notice that the corn is split into ground yellow corn and corn gluten meal) where they should be, this is a corn diet with some chicken by-products added. This diet is bad enough, but the new, scientifically-studied diet is all corn?

We won’t be recommending this one.

For more information contact Dr. Jeff Grognet or Dr. Louise Janes at

Mid-Isle Veterinary Hospital
5-161 Fern Road West
Qualicum Beach, BC
Tel (250) 752-8969

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