New Study Reveals Certain Cat Foods Could Damage Kidneys Within Weeks

A shocking new study carried out by veterinary scientists in Munich shows that high phosphorus in certain cat foods can damage kidney function in cats.

Before the investigation, scientists didn’t know why 35% of older cats suffered from chronic kidney disease. But the results of the new study suggest that excess phosphate in a cat’s diet could have dangerous effects on kidney function, and “could contribute to the high incidence of chronic kidney diseases in elderly cats,” according to Professor Ellen Kienzle, the lead investigator and author of the study. The new findings appear in the Journal of Feline Medicine and Surgery.

Tests of commercial cat foods available in Germany, carried out by the consumer organization Stiftung Warentest, revealed that, in particular, moist cat food formulas contain on average several times the amount of phosphorus required to keep cats healthy, which might be sufficient to “damage the healthy feline kidney within a few weeks,” the scientists revealed.

The majority of cats in Germany are fed complete prepared cat foods. Typically, cat foods, especially moist foods, provide, on average, four to five times the phosphorus maintenance requirements, but the maximum concentration of phosphorus in some cat foods covers nine times the maintenance requirement.

As the authors explain, phosphates in animal foods are in part derived from natural sources, mainly bone and cereals, “However, pet-food manufacturers also add inorganic phosphates to achieve the appropriate texture and extend shelf life.”

Now the authors plan to look at the impact of excess dietary phosphate on the health of dogs and it is now the subject of a dissertation in Kienzle’s working group. The initial results suggest that the concentration of phosphate in the blood rises significantly “following the intake of inorganic phosphates.”

How does this study relate to pets in the U.S.? While no one can say for certain, it’s possible, we may be able to extrapolate the results of the study presuming the pet food market in the EU is not that different than it is in the U.S., however, the EU follows maintenance requirements according to the National Research Council and the European Pet Food Industry Federation.


If you believe your pet has become ill from consuming a pet food, please provide the FDA with valuable information by reporting it electronically through their Safety Reporting Portal or call your local FDA Consumer Complaint Coordinator.

If you and your veterinarian think a pet food or treat is the source of a problem – save it – because your state agricultural or veterinary diagnostic lab may want to do testing. If you need more help, find out how to report a pet food complaint to the FDA.


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Mollie Morrissette

Mollie Morrissette, the author of Poisoned Pets, is an animal food safety expert and consumer advisor. Help support her work by making a donation today.

Comments (7) Write a comment

  1. So… What is the safest cat food to buy???? Seems like that would be found somewhere on this site.. Im not seeing it yet..


    • That’s because I don’t do pet food reviews. The advice I give everyone is buy a human edible/human grade pet food. That’s the bright line that separates good pet food from “I don’t know if I can trust it” pet food. Start from there and you’re in pretty good shape for finding a pet food that is good enough for people to eat – the rest is a big black hole where the laws governing the manufacture of pet food are not as stringent as the ones governing human food. The distinction between the two is vast.


    • Oh no! You’re not getting a thank you? OMG – I changed my donation route and something must have broke. :( Thank you for alerting me. I am blessed everytime someone goes out of their way to thank me for the work I do. It is so much appreciated because working 14 – 18 hours a day – 7 days a week without pay is a financial struggle. Basically, I live on a shoestring. But, with help from people like you, I am encouraged to keep going because every little bit really does mean the world to me. So, thank you, Charmaine.


    • I’ve donate to many organizations and never requested a thank you. Strange that you feel need to be recognized. 🤔


      • Thank you, Cynthia!

        I cannot thank you enough for your donation! I am deeply grateful for your recognition of the work I do. It is a labor of love and dedication to animals and in particular to pets and their caregivers.

        Donations are the only way this work can continue as I receive no other form of financial assistance from any source. While I would like to say it is adequate, it seldom is. I struggle just to pay for the costs of running the site, believe it or not.

        So, your donation means I can breathe a little easier this month. And I am sustained by your generosity and appreciation of the work I do.


      • Cynthia,

        Gratitude is always as good thing and it works in both directions!

        There is nothing “strange” about the desire to be appreciated!



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