Unveiling the Truth: Is Fish Safe and Nutritious for Your Cat?

4/10/17

Unveiling the Truth: Is Fish Safe and Nutritious for Your Cat?

Fish is not a natural part of a cat diet, and yet, so many cats love it. To some extent, it’s because pet food manufacturers offer a large variety of fish-based foods. Unsuspecting cat parents think they’re treating their feline friends with a fresh can of tuna, when the truth is, they may be harming their health. 

While it’s tempting to indulge a finicky palate, canned fish is not always good for your kitty. That said, responsibly sourced fresh fish or fish oil supplements may carry some benefits for your feline as part of an ancestral diet. 

To answer the question should cats eat fish once and for all, read on for a full breakdown of the benefits and drawbacks.

Benefits of Fish for Cats

While canned fish is likely a danger to your kitty (more on that in a second), fresh fish or a fish oil supplement might offer certain health benefits in moderation. For instance, raw fish is protein-packed, and can help cats build lean muscle while burning fat to maintain a healthy weight.

Not only does high-quality raw fish help your pet maintain a trim physique and muscle tone, it can also promote a plush, shiny coat, bright eyes, and healthy gums. Moreover, the scent and taste of fish are tantalizing to cats, so offering fish may tempt a cat who has been refusing to eat.

Omega-3 and Omega-6 Fatty Acids

Cats require both Omega-3 and Omega-6 fatty acids for optimal health. They are considered essential fatty acids, meaning they cannot be manufactured in the body and therefore need to be obtained through a cat’s diet. Fish oil is an excellent source of both.

Omega-3 fatty acids help reduce swelling, relax blood vessels and airways, improve circulation and reduce blood clotting. Conversely, Omega-6 fatty acids help increase swelling, constrict blood vessels and airways, reduce circulation and increase blood clotting. This is important when the body is injured or develops an infection. 

Wild-caught fish, like sustainable salmon, sardines, and anchovies from cold waters with low levels of mercury and other heavy metals are an excellent source of Omega-3 and 6.

Whether given as a supplement, included in a commercial cat food, or served fresh, it is important to be familiar with the source of any fish or fish oil  to add to your cat’s diet.

Risks of Fish for Cats

While fish is a classic favorite with cats and high-quality, wild-caught fish may offer certain health benefits, there are notable risks of feeding your cat fish that you should take into consideration. Read on to learn why a fish-heavy diet might not be the best idea for your pet.

Fish Might Cause Kidney and Urinary Tract Issues

The cooked fish used in canned pet foods is generally either whole fish or by-products from fish that can’t be used for human consumption. This mix may include guts, feces, and fish bones. These are high in phosphorus and magnesium and can present problems for cats, especially those with kidney or urinary tract disease. In some cases, sensitive cats can develop cystitis and even urinary blockages if they eat any fish at all.

Fish is a Common Feline Allergen

If you’re considering what can cats not eat, after beef and dairy products, fish, having been identified as one of the most common feline allergens (cats in particular are more commonly allergic to fish than other pets like dogs), may cause gastrointestinal problems like frequent vomiting or loose stools. The immune response associated with an allergic reaction may also cause itchy or infected skin.

Fish Contains High Levels of Mercury

Studies show that many cat foods contain levels of mercury above the maximum levels recommended by the National Research Council. Particularly foods with tuna as the first ingredient, followed by other seafood-based ingredients like salmon or crab, were likely to contain dangerous amounts of mercury. 

Chronic mercury exposure can cause digestive issues, as well as problems with the kidneys and brain (and your cat is even more at risk if he or she eats the same food every day).

Fish May Be Contributing to Higher Instances of Hyperthyroidism

Polybrominated Diphenyl Ethers (PBDEs), found in some canned cat food, may be playing a role in the increase in feline hyperthyroidism. PBDEs are flame retardants commonly found in building materials, furniture, carpeting, and textiles. Feeding fish-flavored foods only compounds the exposure of toxins already present in the cat’s home environment.

Fish near the top of the food chain, such as tuna and mackerel, two proteins widely used in fish-flavored cat food, often contain high concentrations of PBDEs.

Types of Fish Commonly Used in Cat Food

Each of the following types of fish are common first ingredients in canned cat foods. While each offers certain health benefits when eaten fresh, each has its own risks when present in a canned cat food recipe (and may even be an allergen for your kitty).

Salmon

Salmon is one of the most common ingredients in fish-based cat foods. This protein-packed, brain-healthy fish is also a staple in the human diet, so you might be wondering: Can I give my cat salmon? Read on for the associated risks and benefits.

Benefits of Salmon

Salmon is rich in nutrients like vitamins B3, B5, B6, B12, D, and E, as well as selenium, potassium, and both EPA and DHA omega-3 fatty acids. This protein-packed fish is beloved by cats, so it’s a good one to try if your cat’s appetite has been dwindling.

Risks of Salmon

Most salmon used in commercial cat food is farm-raised, not freshly caught. Fish farms are a form of factory farming, where the farmed salmon are kept in overcrowded pens in coastal waters which are often polluted with PCBs, pesticides, and other contaminants. Farmed salmon are also fed antibiotics to limit the spread of disease, and dyes to make their flesh “salmon-colored.”

Moreover, raw salmon can contain harmful bacteria and parasites, so if you’re wondering, “Can I give my cat raw salmon?” The answer is that it’s about as risky as any low-quality sushi.

Tuna

Tuna is another fan favorite with cats, and is the first ingredient in many cat foods. If you’re wondering, “Can I feed my cat tuna?” The answer is that while tuna may tempt a finicky cat to eat, its risks ultimately outweigh its benefits. 

Benefits of Tuna

Tuna is protein-packed, cheap to buy canned, and contains a variety of nutrients, including omega-3s (far more DHA, but some EPA as well), vitamin D, selenium, calcium, magnesium, potassium, and iodine. DHA omega-3s in particular support brain and eye health. Fresh tuna, while a bit more expensive than cooked fish, is not nearly as high in sodium. 

Risks of Tuna

Tuna and other predatory fish eat smaller fish. They may be at the top of the food chain; however, this also means they often accumulate higher levels of heavy metals (including mercury) as well as PCBs, pesticides, and other toxins. 

Mercury levels in tuna are such a big concern that the FDA recommends only one serving of albacore tuna per week for humans. 

Additionally, tuna is highly addictive to cats. Cats fed tuna regularly may refuse to eat anything else.

Tilefish (aka Ocean Whitefish)

Tilefish, often listed as “ocean whitefish” in ingredients lists, is a common ingredient in canned cat foods. If you’ve noticed tilefish or ocean whitefish in your cat’s food, you might be wondering whether it’s safe for cats to consume regularly. While tilefish is generally a healthy and sustainable option, canned tilefish pose many health risks to cats. 

Benefits of Tilefish

Tilefish are mild in flavor and considered eco-friendly (as they are not an overfished species, are widely available year-round, and are fished responsibly). They’re low in sodium, high in protein, and rich in nutrients like phosphorous, niacin, selenium, and vitamin B12.

Risks of Tilefish

Tilefish, usually labeled as Ocean Whitefish, is among the most contaminated types of fish in most cat foods (meaning it contains high levels of heavy metals like mercury and PCBs). These fish are so toxic to consume that the FDA advises women of child-bearing age and young children to avoid them entirely.

The Bottom Line: Skip the Fish

Hearkening back to cats’ representation in the cartoons of our childhoods (we all remember Tom from Tom and Jerry cooking the goldfish), fish is seemingly a feline favorite. What’s more, we’ve all been taught that fish are “brain food” and an excellent source of protein.

However, while fish can be a relatively nutritious choice for a cat who refuses to eat otherwise, the processed fish listed as a first ingredient in many canned cat foods is often contaminated with heavy metals, pesticides, and other toxins. Considering that many cats are also allergic to fish and that fish may cause thyroid, kidney, and urinary tract issues for your pet, it’s best to avoid serving your feline companion fish whenever possible.

Select Natural Selections

If you’re looking to feed a finicky feline, you may feel lost without fish as an option. Never fear—Darwin’s offers a selection of natural pet food that’s guided by your cat’s ancestral diet, so it’s sure to be a hit with both his palate and stomach.

Our line of natural cat food is made from 100% real chicken, turkey, and beef (no fish), is minimally processed and free of chemical preservatives. Plus, these complete and balanced meals meet the Association of American Feed Control Officials’ guidelines, so there’s no need for additional vitamins or supplements. 

Even if your cat is facing kidney issues and has specific dietary needs, such as during cat pregnancy, our Intelligent Design line of raw cat food has her covered. So ditch the can of tuna for a blend inspired by nature and informed by science.

Sources: 

North Carolina State University. De Facto Cat: Three Protein Choices: Chicken, Fish, and ?. https://defactocat.wordpress.ncsu.edu/2021/02/27/three-protein-choices-chicken-fish-and/

Tufts University. Should I give fish oil to my pet? https://vetnutrition.tufts.edu/2018/06/should-i-give-fish-oil-to-my-pet/

University of Nevada, Reno. Mercury levels in pet food cause for concern, fish-based foods the main culprit. https://www.unr.edu/nevada-today/news/2021/mercury-in-pet-food

State of Michigan. Mercury Spills & Your Pet. https://www.michigan.gov/mdhhs/-/media/Project/Websites/mdhhs/Folder2/Folder18/Folder1/Folder118/Mercury_Spills__Your_Pet_MDCH.pdf

Tufts University. What every pet owner should know about food allergies. https://vetnutrition.tufts.edu/2017/01/food-allergies/

Global Salmon Initiative. Nutrition. https://globalsalmoninitiative.org/en/about-salmon-farming/nutrition/#:~:text=(100%20g)%20portion%20of%20farmed,concern%20in%20the%20United%20States.

FDA. Fish and Fishery Products Hazards and Controls Guidance. https://www.fda.gov/media/80637/download

Healthline. Is Canned Tuna Good for You, or Bad? https://www.healthline.com/nutrition/is-canned-tuna-healthy

NOAA Fisheries. Golden Tilefish. https://www.fisheries.noaa.gov/species/golden-tilefish/overview

FDA. Selecting and Serving Fresh and Frozen Seafood Safely. https://www.fda.gov/food/buy-store-serve-safe-food/selecting-and-serving-fresh-and-frozen-seafood-safely#:~:text=The%20highest%20methylmercury%20levels%20are,should%20avoid%20these%20seven%20fish.


The Conscious Cat

Ingrid King is the publisher of the multiple award-winning website The Conscious Cat, and author of five cat books. She shares her Northern Virginia home with her two tortoiseshell cats, Allegra and Ruby. 

 

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