In this video Dr. Karen Becker talks about the good, the bad and the ugly of feeding fish as a protein source for dogs and cats.
By Dr. Becker
Today I want to discuss all the buzz surrounding fish as a protein source in pet foods.
Unfortunately, the majority of seafood these days is loaded with toxic metals like mercury.
Many types of fish are also contaminated with industrial chemicals like PCBs, dioxins, and pesticides like DDT.
These toxins are absorbed by the smallest ocean plants and animals at the low end of the food chain.
As larger ocean dwellers come along and consume these contaminated plants and prey, the toxins accumulate and become more concentrated in the bodies of the bigger fish.
Unfortunately, the largest predators in the ocean end up heavily laden with toxins.
This includes tuna, which many people regularly feed their cats. Some dogs, but mostly kitties, end up eating a lot of potentially contaminated tuna.
Ethoxyquin: A Potentially Deadly Preservative in Pet Food Containing Fish
The fish in pet food is heavily preserved during the manufacturing process using a chemical preservative called ethoxyquin, which is known to be a cancer-causing agent.
Ethoxyquin is banned from use in human food except in very small quantities allowed as preservatives in spices.
I have experienced first-hand the heartache of ethoxyquin poisoning with my best friend, Gemini, a Rottweiler.
When Gemini was seven and I was in my sophomore year of vet school, she went into liver failure after consuming food containing ethoxyquin. I got the food for free from a major pet food manufacturer who was giving away the stuff to vet students.
It was determined Gemini's liver failure was caused by the ethoxyquin in that food.
Needless to say, not only was I overwhelmingly disturbed that I had unintentionally harmed my dog, but I became very angry that a major 'veterinary line' of dog food contained chemicals that had the potential to kill the pets we were learning how to save as vet students.
It was then and there that I committed not to feed Gemini processed food ever again. It was actually the beginning of my quest to have clean, healthy, pure foods in the pet food supply chain, which is an ongoing battle to this day.
It's Really Hard to Avoid Ethoxyquin in Formulas with Fish Meal
Unfortunately, ethoxyquin is still being used in many pet foods currently available on the market. It is used to preserve the fat in almost all fish meals – fat that is made from waste products.
Always remember that if the label doesn't list exact ingredients, including the exact meat source, you have absolutely no idea what's in that food. And because ethoxyquin is added before the raw ingredients are shipped to the pet food manufacturers, it doesn't get listed or disclosed on the product label.
The pet food company you purchase your cat's or dog's food from may not be adding ethoxyquin, but that doesn't mean it isn't in the fish meal in that food.
Don't make the mistake of assuming if the fish meal product label doesn't list ethoxyquin, it's not in there. Unless the label specifically states the formula is ethoxyquin-free, or you call the manufacturer's 1-800 number and are told it's not in the raw materials they purchase nor added during their own manufacturing process, you should assume the formula contains ethoxyquin.
Fish meal also happens to be one of the main pet food ingredients also contaminated with mycotoxins.
Then What Kind of Fish Can I Feed My Cat? Aren't Cats Designed to Eat Fish?
It's true cats seem to love seafood meals, but it's weird because kitties didn't evolve to eat fish.
Your favorite feline's ancestors came from the deserts of Africa. They didn't hunt giant tuna – or anything else -- in the sea. Your kitty's natural prey are small furry land dwellers like mice.
Because cats seem to love fish and the people they own love feeding it to them even though it's not their natural prey, it could be why kitties fed a lot of canned tuna run an increased risk of acquiring squamous cell carcinoma.
But even though the natural diet of cats isn't seafood, they absolutely can get addicted to fish.
And in fact, kitties tend to become addicted to any protein they consume exclusively. Pet food companies are acutely aware of this phenomenon, which is why most cat food formulas are either fish or chicken based. These are the proteins cats most often form addictions to.
Other Health Concerns from Feeding Fish
As many of you know, I talk a lot here about the need to rotate proteins in your pet's diet. That's because any food that is over-consumed can create an allergy over time.
And fish, as it turns out, is one of the most highly allergenic foods for felines. Allergies cause systemic inflammation. Cats that eat allergenic foods over and over can end up with lung inflammation that can also lead to asthma. And of course asthma is one of the more commonly diagnosed inflammatory conditions in cats.
There also appears to be a link between mercury and asthma, and ethoxyquin and asthma, so it's easy to start to see the bigger picture with regard to diet-related inflammatory conditions.
Fish fed in high amounts can also lead to thiamine deficiency, which can cause loss of appetite, seizures, and even death.
Long-term ingestion of fish in cat food can also deplete vitamin E resources. Vitamin E deficiency can also cause a really painful condition called steatitis, which is yellow fat disease. If left untreated, steatitis can also be life-threatening.
Seafood is a very rich source of iodine, but cats aren't designed to process a lot of iodine. Many animal nutritionists, including me, believe there's a link between cats consuming too many iodine-rich foods and hyperthyroidism.
There's also been a link established between pop-top cans or canned cat food and hyperthyroidism.
Pet food companies are now introducing 'low-iodine' formulas for hyperthyroid cats. How about we just avoid feeding cats fish-based food instead? Avoiding foods high in iodine seems like a good way to prevent hyperthyroidism in kitties.
Last but not least, the magnesium content in fish has been linked to urinary tract diseases in cats. A diet overloaded with the mineral magnesium can predispose your kitty to magnesium ammonium phosphate crystals, also known as MAP crystals or struvite crystals. Crystals are a big problem for many, many cats.
Is There Any Safe Fish to Feed Pets?
It may seem like I'm anti-seafood in general, but I'm really not. However, I do recommend you be very choosy about the fish you feed your pets. And I certainly don't recommend feeding an exclusive diet of fish protein to dogs or cats.
Fish are a rich source of omega-3 fatty acids, which are essential to your pet's well-being. If you supplement your pet's diet with fish, I suggest you use sardines packed in water. Sardines don't live long enough to store toxins in their bodies, and they're a terrific source of omega-3s.
Feeding wild caught salmon in rotation with other proteins is also an excellent way to get those omega-3s into your dog or cat. If you choose not to feed any fish, I recommend you supplement your pet's diet with krill oil or another omega-3 fatty acid.
I also recommend you scrutinize any fish-based commercial pet foods you may be feeding. As with any pet food, there can be quality issues.
Substandard ingredients are added to pet food, which means the runoff from the human food industry ends up in pet food formulas. And chances are there is mercury, ethoxyquin and other potentially carcinogenic preservatives in those fish-based diets.