Cat Food: What to Feed & What to Avoid

You are what you eat. So are your cats.


Sophie grooms
Our experience is that much illness can be prevented and/or healed with proper feline nutrition. This is not a substitute for proper medical care but a partner in your cat’s health.

Cats are obligate carnivores. This means they must have meat to survive, unlike the omnivorous dog, who can survive on a wider variety of food.

Another difference is that cats have a relatively short digestive tract with a smaller stomach, compared to dogs (and humans). Cats’ livers are also lighter and much more simple than dogs, having evolved for lots of travel while hunting. Because they lack essential enzymes and amino acids, they simply don’t have the capacity to digest other food sources, like vegetable matter or fruit.

Your cat’s health depends on eating feline-appropriate ingredients in its food. The ideal diet for a cat is a mouse, which has around 55% protein and 23% fat. While there are sources for whole frozen mice to feed your cat, most people aren’t up to that task and rely on commercial or homemade cat food. It’s also just as important that your cat not be exposed to cat-inappropriate ingredients that may be toxic for it in the long run.

There is no consensus, either in the veterinary world or the pet consumer world, on whether to feed wet food, dry food, or homemade food. This is a choice best left to you and your lifestyle as your cat’s guardian.

As the 2007 pet food recalls showed us, even the most premium pet food brands have been known to put questionable ingredients in their food. It’s up to us to become well-informed consumers and choose the best food to keep our cats and kittens healthy.

We’ve drawn on the best research we can find for this article. We offer some parameters for what to look for in your cat’s food and what to avoid. Please see our article What Should I Feed My Cat for more specific recommendations. Feel free to contact us if you have any other information regarding any of these ingredients. We’re always open for new information!


According to the AAFCO, adult cats can survive on 26% protein, while kittens and lactating queens need 30%. However, a mouse is around 55% protein, so a higher protein content will enable them to thrive, not just survive.

While the AAFCO definition of “by-product” can contain good ingredients such clean internal organs, pet food manufacturers are also allowed to include everything from sick slaughterhouse animals to euthanized animals to expired junk food. Since there is no consistency to the mix, it’s best to avoid this source.

Look for whole sources of protein, like whole chicken, turkey, eggs or fish. The best sources are from animals the cat could conceivably kill, with amino acid ratios appropriate to feline kidneys. This means chickens, turkeys and other small birds with occasional eggs and fish. “Meal” means the fat and water of the protein have been removed and is usually a satisfactory source of protein, since it’s more concentrated, but make sure the animal is specified.

What to avoid

  • Any non-specific meat: especially by-products which can contain any form of animal matter (i.e., skin, fur, organs, etc.) and residual matter from processing which are unhealthy choices.
  • Meat by-products: especially as the initial meat ingredient, avoid to ensure good long term health.


While the AAFCO puts minimum fat needs at 9%, a mouse would be around 23%. 15% fat is a good compromise. The fat source should be from a specific animal.

What to avoid

  • Beef tallow: a cheap and undigestible fat source for cats
  • “Animal fat”: the fat from rendering questionable sources of protein, which can include euthanized animals and the drugs used to kill them with, among other toxins.
  • Vegetable fats like flax and safflower oil: cats can’t convert this to the appropriate fatty acid.


A cat’s natural prey like the mouse would be around 3% carbohydrates. Cats actually have little metabolic need for carbohydrates and no way to convert carbs to energy, the way dogs and humans can. Grains are added to dry kibble to make it easier to handle for humans. The most appropriate grain for cats, according to research, is rice, and the most appropriate form for rice is rice bran. It should come after the protein sources in the list of ingredients.

What to avoid

  • Wheat and soy: known allergens for cats
  • Wheat fiber: a known irritant for cats.
  • Corn: proven to have more bioavailable protein than other grains, but still less appropriate than meat sources.
    NOTE: Corn and soy also have a very good chance of being contaminated with genetic modification (GM). Some estimate up to 80% of non-organic corn crops have been genetically modified. None of these GM crops have even been studied in the long run for their affect on humans, much less on cats. Unless you want yourself and your pets to be unpaid research subjects for corporate agriculture, you might want to avoid these products.
  • Potatoes and sweet potatoes: there is presently no published research on the effects on cats of newer carbohydrate additives such as potatoes or sweet potatoes. Until the manufacturers can show proof these ingredients are safe, it’s probably best to avoid them.
  • Gluten: many formulas have gluten as a source of carbohydrates as well as protein. Gluten was proven to be a risky ingredient imported from China in the form of melamine during the 2007 pet food recalls that killed millions of companion animals.


Up to 90% of the immune system response lies in the intestine. Fiber plays a huge role in making sure the intestine is healthy. Rice bran and beet fiber have proven to be good sources of fiber for felines in that they provide the fermentability for good bacteria as well as not lowering the digestibility of the rest of the food.

What to avoid

  • Cellulose: the least fermentable fiber for felines. This may push the food through too quickly for proper nutrients to be absorbed.
  • Oat fiber, peanut hulls, psyllium gum, soy hulls, citrus pulp and lactulose are also not fermentable by cats, according to research, acting like cellulose in the gut.
  • Fructooligosaccharides (FOS), guar gum, locust bean gum and citrus pectin are actually too high in fermentability and can cause gas, diarrhea and loss of nutrients.
  • Peas & pea fiber: another inexpensive filler and highly insoluble. Note there is zero research available on its effect on cats.


Cats need most of the same vitamins and minerals that dogs do, with the following exceptions. Cats need more Vitamin A than dogs because they can’t convert beta carotene. They also need twice the amount of B Vitamins: (Thiamine, Riboflavin, Pyridoxine, Pantothenic Acid, Niacin and B-12). Most commercially prepared diets contain the recommended amounts of vitamins and minerals for cats and it can be dangerous to supplement past minimum requirements.

What to avoid

  • Vitamin K3, otherwise known as Menadione or Menadione Sodium Bisulfite or Bisulphate: a cheap and artificial form of Vitamin K that causes many serious side effects. This is banned for human use here in the US as well as in Europe.


A vet once said that if cranberries were good enough for him, they were good enough for his cat. Based on that reasoning, he should be thriving on a primarily protein diet of mice, small birds, eggs and fish. That’s not the case, of course.

The only well-researched sources of vegetable nutrition for cats are pumpkin, rice bran and beet fiber. Many cat foods, especially higher-end ones, are marketed toward the human, not the cat. This leads to unresearched additives like tomatoes, blueberries, cranberries, potatoes, carrots, spinach, apples, zucchini…the list goes on. In addition, avocados have been found to be toxic to cats.

Cats suffer with less research funding than dogs have, so many of these ingredients have not been proven to be safe. Cats’ simpler livers lack certain enzymes and amino acids to process these ingredients which are exotic to the normal diet of cats. Until the pet food manufacturers can prove the safety of these ingredients, it’s simply unnecessary–and downright dangerous–to feed your cat food that has these in it.

What to avoid

  • Cranberries: a growth industry from overproduction of cranberries, with no research to guarantee either safety or health improvement, especiall in cats. In fact, the benzoic acid of cranberries has been proven toxic to cats.
  • Blueberries, apples, acai berries, tomatoes or any other fruit: no research to support their safety.
  • Carrots, spinach, turnip greens, zucchini, green beans or any other vegetable but pumpkin: no research to support their safety.
  • Avocadoes: all parts are toxic to animals and research says, “Feeding avocados to any non-human animal should be completely avoided.”


Again, cats’ livers cannot process many of the same things dogs can, so you should never assume the safety of exotic ingredients unless your pet food manufacturer can show you the research. Many herbal additives, such as yucca, alfalfa, green tea and parsley are included as enticements for the cats’ humans, with no proof of their safety for the cats themselves.

What to avoid

  • Yucca Schidigera Extract: purported to decrease the odor in feces, Yucca is on many lists of plants toxic to both dogs and cats.
  • Rosemary Extract: cheap preservative known to cause seizures in cats and small dogs and not proven safe, either in the US or in Europe.
  • Alfalfa, green tea, parsley, licorice root, angelica root, fenugreek, marigold, fennel, peppermint, chamomile, dandelion, savory, or any other herbs: no research to support their safety.


Mixed tocopherols (Vitamin E) have been proven to be safe and effective preservatives in cat and dog food. Recently, manufacturers have begun to add cheaper and more deadly preservatives to their formulas.

What to avoid

  • Ethoxyquin: actually a pesticide which may compromise your cat’s health over time.
  • BHA & BHT: cheap chemical additives not proven to be safe.


This is an odd category, but must be included for canned cat food, since almost all brands have some in them.

What to avoid

  • Carrageenan: a known cancer-causing substance for humans, it is also known to produce intestinal lesions, ulcerations and tumors in experimental animals. Can be avoided in some canned cat food.
  • Guar Gum: shown to decrease the digestibility of protein in cat food. Very sticky substance that may cause canned food to stick more to cats’ teeth. Hard to avoid in canned food.


Cats can only see minor variations in color, so any bright colors in food are put there for the humans, not for the food. No food coloring has proven to be safe for felines, so if your cat’s food isn’t meat colored, avoid it.


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Board on Agriculture (1986) Nutrient Requirements of Cats, Revised Edition. Retrieved from:

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Sunvold, G. D., Titgemeyer, E. C., Bourquin, L. D., Fahey, G. C., Reinhart, G. A., (1994) Journal of Nutrition: Fermentability of Selected Fibrous Substrates by Cat Fecal Microflora

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