Evidence That Fish is Actually Bad for Cats?

Where is the evidence that fish is bad for cats? Well, obviously a JUST fish diet is bad, but why are fish based foods bad? I've been seeing it everywhere that people say don't feed fish, etc but they have nothing to back it up. I've been a cat owner for 12, going on 13 years now and I've never heard of these claims until now. In theory, fish causes urinary issues, I don't believe this to be true as I had a male with severe urinary issues and he was put on a fish based diet and it went away? My vet proved it.


Help? I want solid advice from a vet or pet nutritionist or websites/books on it. Opinions welcome but I want to see facts. Thanks!

New indoor cat owner so take anything I say with a grain of salt   I'm strictly basing my information on catinfo.org a site by a vet, whom says that fish is bad for cats with urinary issues, due to the bone meal. All processed canned food with fish, does have bone meal in them which evaluates the phosphorous counts. That & other minerals is what helps to build crystals, possibly resulting in blockage.

Hmm... thanks!

Mainly because it is high in phosphorus and a lot of fish actually contain Mercury. Most notably, Tuna.

Unfortunately my 3 kitties will NOT eat ANYTHING that doesn't have some kind of fish or seafood in it.

They don't like chicken or turkey or beef or lamb. Haven't tried rabbit yet but I doubt they will like it haha.

There's this study which linked fishy based foods to hyperthyroidism. I fed my cat fish based kibble for a large majority of his life (til i learned better, of course) and he developed hyper-t. Coincidence? Maybe, but science says maybe not.

It's funny I am seeing this post regarding this subject! I just saw one claiming fish is so bad and "don't ever feed your cat tuna" and "don't ever feed your cat tuna and I would only feed mine 1/4 of a tablespoon" , or "I NEVER feed my cat fish", and "that fish causes neurotoxicity because of mercury" and so forth. I was so irritated trying to post back in that post but I couldn't comment for some reason!

I am completely with you!! And then someone posted a research article as "evidence" regarding 16 kittens that were fed an ONLY tuna that were all intentionally mercury contaminated fish for 11 months as their ONLY diet. I think 2 out of 16 died and the third showed signs of Neuro deficits but symptoms resolved. It didn't state what sickness ultimately killed the kittens, only that they had signs of neuro deficits while they were alive and that they found lesions in their brain in the cerebellum region and were positive for Mercury. Well, no crap! Of they were positive for mercury! They were ONLY GIVEN INENTIONALLY MERCURY CONTAMINATED TUNA AS THEIR DIET for a year before they basically killed them to look at their brain. They obviously kept feeding the poor kittens the mercury contaminated fish EVEN after they were ill and needed care and obviously something else in their diet. The part I read indicated how many milligrams the fish were intoxcated with of mercury but I can't remember how much and even So I don't really know how much the fish we eat may possibly have to even compare but even if they do I highly doubt it's even REMOTELT close to what they were feeding these kittens even for 1 solid meal. This study actually disgusts me. It disgusts me because they purposely were feeding these baby kittens diseased and mercury infested fish and ONLY that for their diet caged up in probably filth with obvious no concern over their health in general. And what does that prove??? Common sense tells you it proves ABSOLUTELY nothing regardless if they found a lesion on their brain or not. That makes me so angry to put these kittens through a worthless test and then for people to actually be so ignorant to read that and pass it around for other people to read that also read it and obviously have no common sense when it comes to how a cats body works much less a human body and have no idea what goes on in lab based studies on an animal.

Another commenter stated as you "oh because of the mag and phos levels" and one commenter went so far as to say that she knew it was "bad for the body because it converted chemically to CaPho...." Yes, they actually said that. Phosphate works with calcium in the body but does not contain calcium. Phosphate is phospherous and oxygen molecules. I am sorry to get technical and by no means am I smarter than anyone else nor am I claiming to be. I am not a vetenarian or a physician but I am a RN recent graduate ARNP that works in trauma and currently back in school again. And while the human body is different than a cats , it isn't really that much different.

The theory behind the phosphorous and magnesium levels are based off rumors at and reading about kidney disease and elevated phospherous, magnesium levels. Fish has been said as something to avoid with kidney stones in humans and is "bad for the kidneys". All of these misconceptions is where the fear of fish starts I suppose. I know this post is long but this sums up these traditional rumors and fears with some biological logic behind them to hopefully maybe help someone understand better.

Kidneys, in both humans and cats, have a much larger job than just "filter blood". They keep our body in homeostasis. One of their essential roles is in the homeostasis of these ions (phospherous, calcium, etc).The kidneys also allow us to absorb vitamin D and it produces a hormone called erythropoetin that stimulates the bone marrow to make red blood cells which is why many kidney patients become anemic. Calcium, phospherous, potassium, and magnesium are multivalate cations and among some of the most important things the kidneys regulate. Calcium and phospherous are stored in our bone but are also found in our blood. Calcium, for example, is found in both the intracellular and extracellular spaces playing a vital role in nerve impulse transmission, muscular contraction (including the heart), blood coagulation etc. Both are important in the body but just as many other things, having to much or to little can cause problems for the body as do other electrolytes such as sodium, potassium, magnesium that become unbalanced. They primarily only become unbalanced (in spite of specific diseases) and in excess when the kidneys are in FAILURE. When the patient is in renal failure, only then do we consistently monitor levels of phospherous, potassium, calcium because they can build up in the body because the failing kidneys are not excreting them like they should. Let me say that again. The kidneys are weak, damaged and in FAILURE so they aren't working properly which results in a buildup of these things because they normally are filtered and balanced when the kidney are working properly. All of these ions are filtered, transported excreted, etc in different areas of the nephrons in the kidneys and are all regulated with other things in the body such as the digestive system and certain hormones. Which is why some things build up more than others like calcium and phospherous. The parathyroid specifically helps control calcium and phospherous and responds by these high levels by trying to absorb more which triggers the body to make more and it becomes a vicious, ruthless cycle when the kidneys aren't doing their job. I could explain that better and go in more detail but I think I'm already saying to much as it is. So, to SUM ALL THAT UP, CALCIUM,MAGNESIUM AND PHOSPHEROUS DO NOT DAMAGE THE KIDNEYS OR CAUSE PROBLEMS WITH THE KIDNEYS. When the kidneys have failed, typically with CHRONIC RENAL FAILURE is when you should be cognizant of how much of what needs to be monitored and limited.

Another myth is that phospherous and magnesium are related to stones and this misconception leads to it causing urinary tract issues . Phospherous nor magnesium cause ill health in the urinary tract system. Its funny that these people that say this in regards to human stones will say "don't eat fish because of the phospherous" but fail to mention anything about dairy products. Dairy products are overall typically higher in phospherous. They also fail to mention chicken which also has a decent amount in it.

The most typical kidney stone is formed of calcium yet we don't hear people saying to avoid milk etc. In humans there are approximately 6 type of stones and cats 2 majors ones being Struvite and oxalate. There really is no strong scientific evidence supporting what actually causes them and that is agreed upon across the board. And just because a stone contains a certain mineral doesn't mean it is wise not does it mean that limiting it from the diet will help. Soda is recommended to be limited (and makes sense) and some recommend limiting fish while others disagree. Often times (not always) renal stone patients that consume heavy amounts of fish, also consume large amounts of soda. Ironically, the "fizz" in soda prevents calcium from being absorbed. However, one thing we absolutely do know and agree on is water intake. Poor water intake is contributed to stone formation. Increasing water intake helps pass them and helps the kidneys work properly and prevent new ones from forming.

Not only do I think its not harmful to include fish in a cats diet, I also think it is essential. Fish contain "essential" fatty acids that the body can utilize in fighting disease, cancer, inflammation and keeps the skin and coat shiny and healthy. Essential, means the body cannot make it, which is why you often here of taurine being so important. It is an "essential" amino acid. Anyhow, fish are the primary sources of DHA and EPA along with flaxseed and walnuts I believe. These are omega 3's and in my opinion much more healthy than omega 6's. Omega 3's are great for fighting inflammation. So, could be beneficial in supplemented omega 3 to combat inflammatory driven diseases such as asthma and bowel disorders like irritable bowel. Nonetheless, it still is important to include omega 3 in the diet naturally on a regular basis.

Despite, this crazy long post, I could not AGREE with you more on this subject. I just don't understand it. I think some people get carried away and just don't understand it biologically.

jjc1140 said:

Not only do I think its not harmful to include fish in a cats diet, I also think it is essential. Fish contain "essential" fatty acids that the body can utilize in fighting disease, cancer, inflammation and keeps the skin and coat shiny and healthy. Essential, means the body cannot make it, which is why you often here of taurine being so important. It is an "essential" amino acid. Anyhow, fish are the primary sources of DHA and EPA along with flaxseed and walnuts I believe. These are omega 3's and in my opinion much more healthy than omega 6's. Omega 3's are great for fighting inflammation. So, could be beneficial in supplemented omega 3 to combat inflammatory driven diseases such as asthma and bowel disorders like irritable bowel. Nonetheless, it still is important to include omega 3 in the diet naturally on a regular basis.

 

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You realize that most "fish based foods" are using the lowest quality fish possible that likely contain very little to any "essential" fatty acids, right? Unless you're feeding fish you catch yourself or buying something fresh and giving it to your cats, they're eating garbage fish. Yes, omegas are very important to cats (and humans), which is why it's recommended to give your cat an omega supplement, rather than feeding garbage fish that likely is giving them nothing. Fish is also not a "natural" diet of cats, despite the common cultural theme. Fish is also incredibly addictive, and can prevent cats from eating other foods. 

Fish are kinda fishy food wise. For example domoic acid. Fish found to have levels over a certain amount are banned from human consumption and get processed into pet food. It's a matter of quality control, fish in pet food are the rejects of our food and the levels of certain minerals, vitamins, and chemicals may be much higher then what's safe.

Many years back I also was feeding my cats mainly a fish based diet.

Both are seniors and both are hyperthyroid, and both have acquired an allergy to fish. If I open a can of tuna they are all over me, and I give them the tuna water and a small amt of tuna as a treat.

The next few days we have eye drainage going on.

The majority of fish is loaded with toxic metals.

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, who end up eating a lot of potentially contaminated tuna.

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.

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 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.

On top of all of this info is the fact that despite fish not being it's natural diet, they get so addicted to it that they refuse any other foods. And any food that is over-consumed in time will create an allergy to it.

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

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.

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.

So to me, it is not worth the risk of my beloved cats having helath issues from being fed a protein that is not what they were meant and have evolved with.

Cats were originally desert animals and ate animals that crawled, flew or walked. Fish were not a natural part of their diet. Since they have not evolved as much as let's say, a dog has, I prefer not feeding fish to my cats. The mercury and use of ethoxyquin, the use of which does not have to be disclosed by a pet food company,deters me from feeding fish-based foods. I will feed it on a rare occasion and my cats love it but they usually get fed chicken, turkey, duck, rabbit or venison. I usually try to avoid chicken as well as it is a common allergen, as is beef. But I have not seem any issues with my cats. And if my cat with CRF eats it, then he gets it. He needs to eat. So no scientific proof here just personal preference.