Cat food contains too much phosphorus causing kidney damage

A scientific study shows that the levels of phosphorus in commercially prepared cat food (particularly in wet cat food) contains an average five times the amount required to keep cats healthy and because of this it can have a detrimental effect upon kidney function. Cat owners are becoming aware of this. I can tell because they search online for ‘non-prescription low phosphorus cat food’.

“…creatinine clearance, which is measure of the overall performance of the organ, also dropped markedly within 28 days in cats that received a diet rich in phosphorus.”

Cat who had chronic kidney disease (CKD)

My former cat. I loved her.


The study was carried out at the Ludvig Maximilian University of Munich (LMU) by Professor Ellen Kienzle and Dr. Britta Dobenecker of the Chair of Animal Nutrition at LMU et al. It is published in the Journal of Feline Medicine and Surgery (you have to pay to see it).

Complications and lack of clarity

The commercial cat food tested is available in Germany (is it German food and/or American and British?). I don’t have a list of these cat foods. More importantly, it is almost a nightmare to try and find out what an ideal level of phosphorus is for cat food. It is very difficult to compare cat foods by which I mean comparisons between wet and dry foods because you have to apply a formula. It is also very difficult to find out what was considered to be the ideal level of phosphorus in commercially prepared cat food before this study was published (I failed to discover it).

Perhaps the study will change the opinion of pet food manufacturers. What I’m saying is that the list of ingredients on pet food packaging may show us high levels of phosphorus but which are considered to be correct levels.

It is known that phosphorus can damage kidneys. And therefore there has to be very careful preparation and balance in cat food preparation between calcium and phosphorus. This is in order to prevent bone and kidney disorders

List of ingredients and percentages

Pet Food Nutritional Values Comparison, August 2010.xls – Google Drive

If you click on the above link you can see a list of pet foods with a breakdown of their ingredients including phosphorus levels. The “as fed” percentage phosphorus amounts in cat foods is listed which is somewhere around 0.3%. However, the question is, is this an excess of phosphorus when taking into account the LMU study referred to above?

High level of kidney disease

We know that domestic cats suffer from too much kidney disease (35% incidence). It is such a commonplace disease in elderly cats (50% I believe). It almost seems that the majority of elderly cats are dying of kidney disease which begs the question whether commercially prepared cat food is to blame or at least partly to blame.

Further research

I would really appreciate the input of visitors in comments and ask you to do further research on this matter. We need to find out what is the ideal target level for phosphorus in cat food when taking into account the study. As mentioned, and I am stressing this for the sake of clarity, the cat food that they tested was, according to the scientists, far too high in phosphorus to the extent that it was causing kidney damage. Perhaps Susan Thixton (of the can help clarify.

Source of phosphorus

The phosphate in animal foods are partly derived from natural sources such as bone and cereals. Pet food manufacturers add inorganic phosphates in order to achieve a nice texture and to extend shelf life. Perhaps this commercial requirement i.e. to extend shelf life and add texture is a reason why the phosphorus levels are too high. This needs to be clarified.

The study findings tell us that moist cat food formulations contain on average five times the amount of phosphorus required to keep cats healthy. These levels have been regarded as harmless but this attitude appears to be out of date. The maximum levels of phosphorus detected were nine times the amount required which might be sufficient to damage kidneys.


FB comments (see below)


Cat food contains too much phosphorus causing kidney damage — 2 Comments

  1. Your cat Binnie is so precious Michael. My only kitty, Nikki, is 20 years and five months old. She also has chronic kidney disease. I understand your sentiments completely. 😢💜💜

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