Originally Posted by shengmei
As a geneticist, I believe that kidney diseases are due to aging and the lack of clean water in the environment rather than substrates in the food.
Cats in wild only live about six years. Nowadays they can live well into their 20s.
The kidneys can work better, tho', if they don't have to be over worked with trying to filter stuff they weren't made to filter.
Nutrition is tricky - like whole foods, "live" foods - foods that contain everything nature provided "naturally" - are healthier because the body is given everything that it needs to be produce health. (yep, I know this is a "blanket" statement and there are exceptions, like good genetics, etc.)
When you add stuff, cut stuff out, over process stuff, add ingredients that the animal wouldn't normally ingest - then the percentages for potential problems increase.
i.e. When a cat kills a mouse/rat - the cat leaves a lot of the rodent, I haven't seen them eat tails, claws, fur -- well you get the picture :-). This is the same as when they eat birds, they don't eat everything. This is natural. What they naturally consume is what their bodies were made to digest better.
So when our animal food makers add "by products" that our cats wouldn't normally eat, it seems to me that there should be concern -- even more so -- because they _are_ living longer.
Now, I don't think we should "lose sleep" over this issue. But, we do need to be informed, and then do the best that we can, with the resources we have, knowing that this cat, who is living with our family, is most fortunate.