Let’s start by focusing on the positives: commercial cat food is a blessing! It gives us convenient and affordable options for giving our cats the best life we can give them. Without commercial cat food, we’d be forced to make our own food or let our kitties run free outside to catch mice and other critters. 

I recommend a lot of really great cat foods, and most of them are “commercial” options. However, I’ve come across a lot of ingredients to avoid in cat food. Why? They just aren’t something I’d ever want to feed my cat.

You see, since releasing a full database of cat food ingredients, information, and ratings to compliment our “best cat foods” page on my new website, Catological.com, I’ve been neck-deep in cat food analysis. While it’s been eye-opening for me, allowing us to give really high-quality recommendations to our readers, I’ve also been exposed to the “dark side” of the industry.The pet food industry is what I’ll call “loosely” regulated. The FDA has rules and AAFCO publishes guidelines. But, between rendering plants, low-quality ingredients, and foods made internationally, there are a lot of questionable practices conducted by pet food distributors that may surprise you. So, what ingredients should you avoid in cat food?

Let’s examine a list of 15 ingredients that should send up red flags when reading a commercial cat food label.

These cat food ingredients are not necessarily bad or harmful to your furry companion. In most cases, however, extended exposure seems likely to increase the risk of a negative side effect. I suggest keeping this list of what to look for in cat food as well as the bad ingredients in cat food handy so you can make better-informed decisions on your next purchase to keep your kitty happy and healthy.

1. Butylated hydroxyanisole (BHA)

Used as an artificial preservative in food. 

BHA is “reasonably anticipated to be a human carcinogen,” according to The National Toxicology Program of the Department of Health and Human Services (source). While it’s labeled as being safe in low doses, it has been shown to cause tumors in lab animals. So, is this one of those cat food ingredients to avoid?

A little BHA every now and then is unlikely to harm to your cat. But, BHA adds more health-deterioration risks to your cat’s well-being than necessary. This is especially the case if your cat is eating BHA every day. There are better, natural alternatives to preserving your cats’ food.

2. Caramel

Added to some foods to help give it a richer color. 

There is no reason for cat food to be colored, except to make it appeal to cat parents. Your cat does not care what color their food is. Is caramel another one of those cat food ingredients to avoid? Since it is a 100% marketing gimmick, it is unnecessary, and usually a sign of cheap cat food. 

Many coloring options, including caramel, are potential carcinogens (source), or otherwise potentially harmful to your cat.

3. Carrageenan

Red seaweed is used as a thickening agent. 

Carrageenan is a controversial cat food ingredient because one of its forms is a potential carcinogen, called degraded carrageenan. While the degraded form is not used in food applications, some have concerns that it could become degraded once ingested by cats due to their stomach acid; thus, potentially increasing cats’ cancer risk.

Carrageenan may be completely fine (some controversial ingredients are only controversial because they’re not well understood), but with so many other options on the market, many people choose not to take the risk.

4. Cellulose

A filler high in insoluble fiber.

Too much insoluble fiber can interfere with digestion and inhibit protein and nutrient uptake. The worst part is that it’s typically wood pulp (sawdust) from pine trees. Last I checked, cats didn’t eat sawdust! Cellulose is typically indicative of a lower quality cat food.

5. Glucose / Dextrose

Glucose is sugar (plain + simple).

It is not an appropriate ingredient for felines. Glucose could cause obesity and potentially even diabetes.

Dextrose is a crystallized form of glucose.

It is typically used in pet food as a sweetener and as an agent to help develop browning (i.e., to make meat or gravy ingredients look better). Dextrose, like most sugars, can be considered a nutritionally unnecessary addition to cat food and is likely harmful over time. Keep an eye out for this one when wondering what to avoid in cat food.

6. Garlic

One of the main ingredients to avoid in cat food is garlic which can be highly toxic to cats. While we are sure cat food companies who add this for the supposed low-dose health benefits have taken steps to ensure a very small amount of garlic enters the food, it is unnecessary. 

Plus: why take the risk?

7. Glyceryl Monostearate

An emulsifier used in lower-grade pet foods.

Glyceryl monostearate may contain BHA (covered above) and BHT among other glycerols and chemicals. Because its makeup typically contains unknown chemicals, glyceryl monostearate should be avoided.

8. Iron Oxide

Used to color food and give it a more red, meaty color.

Since it is a 100% marketing gimmick, iron oxide is unnecessary, and usually a sign of cheap cat food. This ingredient can even be cultivated from rust! From foodcolor.com: “Common rust is a form of iron oxide. Iron oxides are used as inexpensive, durable pigments in paints, coatings and colored concretes.”

While iron oxide in commercial cat food is likely safe, not readily absorbed into the body, and likely non-toxic, it’s fair to say that any coloring additive is questionable. Moreover, iron oxide has not been thoroughly studied as a food additive, so the overall side effects- good or bad- of ingesting it remains unknown.

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9. Meat & Bone Meal

Described by AAFCO as a “rendered product from mammal tissues, including bone, exclusive of any added blood, hair, hoof, horn, hide trimmings, manure, stomach, and rumen contents.”

Meat & bone meal is one of those rendered products that could contain anything, from euthanized pets to zoo animals to roadkill, to expired meat, and even the styrofoam wrapper it comes in. I know this may sound startling, but some alarming information about the meat goes into these “meat & bone meal” ingredients at the rendering plants.

If you’re not squeamish and want some more reading on this topic, here are a few resources.

10. Meat By-Products

According to AAFCO, meat by-products are “non-rendered, clean parts, other than meat, derived from slaughtered mammals. Includes, but is not limited to lungs, spleen, kidneys, brain, livers, blood, bone, partially defatted low-temperature fatty tissue, and stomachs and intestines freed of their contents. It does not include hair, horns, teeth, and hoofs.”

This means is that anything left over on the carcass after the good, human-grade cuts of meat are removed, gets thrown into a vat and processed. Since it just says “meat,” and not chicken or beef, you have no idea what’s actually in it.

The rules surrounding cat food ingredient labeling allow for less-than-ideal animals to be used in pet foods (see the links above). Like meat & bone meal, meat by-products come from rendering plants that claim to use “4-D” animals as ingredients (i.e. dead from means other than slaughter, like diseased, dying, disabled, and even euthanized pets).

Whether you consider “by-products” a good use of otherwise wasted animal matter, or a just a poor-quality ingredient, there’s no arguing with the fact that unnamed animal products can be bad news.

11. Red, Yellow, and Blue Food Coloring

You will usually find a number after the color, like Red 40, for example. A little food coloring isn’t going to hurt, but it’s been linked to issues like hyperactivity in children and even containing a carcinogen. As mentioned above, there is no reason to add color to cat food. Even if the risk is tiny, food colorings aren’t the best ingredients for cat food and are absolutely unnecessary.

12. Sodium Nitrite

A color and maybe flavor enhancer for meat.

 Upon entering a cat’s body, sodium nitrate may become a carcinogen (source). Whatever the case, flavor and color-enhancing ingredients, like sodium nitrate, are completely unnecessary for cats to consume, whether commercial cat food or treats.

Sodium nitrate is also claimed to be a botulinum controller, but many countries do not use this as an ingredient in their cat food for this purpose.

13. Sodium Tripolyphosphate

Allegedly used as a rancid meat preservative, and used “to help moist foods to retain moisture so that they appear fresher for longer” (source). It’s also a dental additive, used to reduce calcium build-up.

The National Institute for Occupational Safety and Health (a division of the CDC), suspects sodium tripolyphosphate may be a neurotoxin. And the U.S. Environmental Protection Agency (EPA) recognizes sodium tripolyphosphate as “an insecticide, fungicide, and rodenticide.”

14. Titanium Dioxide

A potentially carcinogenic artificial color used as a white pigment. 

Want to know what ingredients to avoid in cat food? This one! Nanoparticles from titanium dioxide have been found to cause a breakdown in chromosomes when ingested. This can cause DNA damage, inflammation, cancer, and genetic disorders in animals. 

15. Wheat Gluten

According to Wikipedia, wheat gluten is “made by washing wheat flour dough with water until all the starch granules have been removed, leaving the sticky insoluble gluten as an elastic mass which is then cooked before being eaten.”

It’s a popular ingredient in a vegan diet because you can use it to make a high-protein, meat-like food called seitan. As an ingredient in cat food, though, wheat gluten isn’t one of the best ingredients in cat food.

For the most part, wheat gluten is used to boost the crude protein numbers, without adding more meat (meat is expensive for manufacturers). In fact, when you see chunks of “meat” in a low-quality food, it is often just chunks of wheat gluten.

The Bottom Line

Don’t panic. Exposure to one or multiple of the bad ingredients in cat food listed above is unlikely to cause your cat issues. But, I would argue that constant exposure to most of the ingredients on this list increases the risk of your cat having health issues. 

There are other ingredients that can be used to make good quality cat food, and the ingredients listed here are typically unnecessary, as they’re only used to keep manufacturers’ costs down.

I recommend finding cat food that is mostly made out of meat with few or no filler ingredients. Look for high protein, moderate fat, and very low carbohydrate options. Foods like this are close to what cats eat in the wild, and it’s what their bodies are adapted to eating since they are obligate carnivores.

— Update: 25-03-2023 — cohaitungchi.com found an additional article Cat Food: What to Feed & What to Avoid from the website happycatshaven.org for the keyword cat food ingredients to avoid.

You are what you eat. So are your cats.

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.

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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 previous 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 note that some ingredients have become so common they are very difficult 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!

PROTEIN

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 as 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.

FAT

While the AAFCO puts minimum fat needs at 9%, a mouse would be around 23%. Around 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.

GRAINS/CARBOHYDRATES

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.

FIBER

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.

Please note that the following ingredients have become so common they will be hard to avoid.

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.

VITAMINS & MINERALS

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.

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Please note that, while Vitamin K3, otherwise known as Menadione or Menadione Sodium Bisulfite or Bisulphate, is banned for human use in the US and Europe, it is extremely common in cat food and difficult to avoid.

VEGETABLES & FRUITS

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.
• Avocados: all parts are toxic to animals and research says, “Feeding avocados to any non-human animal should be completely avoided.”

HERBS & HERBAL ADDITIVES

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.

The following ingredients have become so common in cat food they are almost impossible 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.

PRESERVATIVES

Mixed tocopherols (Vitamin E) have been proven to be safe and effective preservatives in cat and dog food. Some manufacturers still 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.

THICKENERS

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.

FOOD COLORING

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.

REFERENCES

ASPCA (2011) Toxic and non-toxic plants. Retrieved from http://www.aspca.org/pet-care/poison-control/plants/

Association of American Feed Control Officials, 2005-2010, Official publication.

Becker, K. (2011) What dangerous byproducts lurk in cat food? Retrieved from http://healthypets.mercola.com/sites/healthypets/archive/2009/07/21/proper-nutrition-for-your-cats.aspx

Berg, J. (June, 2012) Catnip: the newsletter for caring cat owners: Settling the dry-versus-wet-food debate, p. 7.

Board on Agriculture (1986) Nutrient Requirements of Cats, Revised Edition. Retrieved from: http://www.nap.edu/openbook.php?record_id=910&page=34

Carciofi, A. C. and Brunetto, M. A. Nutritional Management of the Most Common Digestive Diseases in Dogs and Cats Retrieved from http://tinyurl.com/catdigestivediseases

Contreras, S. (2007) Meniodone (vitamin K3). Retrieved from http://www.dogfoodproject.com/index.php?page=menadione

Creighton, P. (2007) Pet food pitfalls. Retrieved from http://petfoodpitfalls.blogspot.com/

Dierenfeld, E. S., Alcorn, H. L., Jacobsen, K. L. (2002) Nutrient composition of whole vertebrate prey (excluding fish) fed in zoos. Retrieved from http://tinyurl.com/preynutrition

Erickson, P. (2010) Feline constipation: gut bacteria and fiber. Retrieved from http://www.felineconstipation.org/gutbacteriaandfi.html

European Food Safety Authority (EFSA) (2012) EFSA Journal: Statement on the safety and efficacy of the product ‘Rosemary extract liquid of natural origin’ as a technological feed additive for dogs and cats. Retrieved from: http://www.efsa.europa.eu/de/efsajournal/pub/2526.htm

Fekete, S. G., Huller, I., Andresofszky, E., Kelemen, F. (2004) Journal of Animal Physiology and Animal Nutrition, Effect of different fibre types on the digestibility of nutrients in cats

Gavin, R. (2005) The Boston Globe: Growers’ pet project. Retrieved from:
http://www.boston.com/ae/food/articles/2005/04/21/growers_pet_project/

Harper, E. J., and C. Siever-Kelly. (1997) Recent Advances in Animal Nutrition in Australia, The effect of fibre on nutrient availability in cats of different ages.

Kovalkovicova, N., Sutiakova, I. Pistl, J. and Sutiak, V. (2009) Interdisciplinary Toxicology: Some food toxic for pets. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2984110/?tool=pubmed

Liquorman, N. (2012) Pet food neurotoxin: rosemary extract & seizures. Retrieved from: http://www.thedogpress.com/DogFood/Rosemary-Neurotoxin-10032_Liquorman.asp

Max’s House Animal Rescue (2011) Feline nutrition. Retrieved from http://maxshouse.com/feline_nutrition.htm

Siegal, Mordecai (1997) The Cornell book of cats: the comprehensive and authoritative medical reference for every cat and kitten, pp. 258-259.

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

Thixton, S. (2009) What ‘kind’ of protein is your pet eating? Retrieved from http://www.truthaboutpetfood.com/articles/what-%E2%80%98kind%E2%80%99-of-protein-is-your-pet-eating.html

Thixton, S. (2012) Carrageenan: just don’t do it. Retrieved from: http://www.truthaboutpetfood.com/articles/carrageenan-just-dont-do-it.html

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Yarnall, C., & Hovfe, J. (2009) The complete guide to holistic cat care.