I've been hearing that younger, newer vets are actually being taught about the real nutrition needs of animals. I have not yet experienced that as all the vets at my local clinic are my age or older and I am 100% certain that I know more about feline nutritional needs than they do. In other words, when they tell me something that is opposite of what I believe, I generally stick to my guns and feed my cats what I think best. One example is those ridiculous dental chews they send home with the cats after dental cleanings. One of the ingredients is corn syrup. No. Just no. Here's a hint: If a dentist tells you, "You don't seem to be doing a good enough job brushing you teeth in between visits, so what I want you to do is chew on some licorice," - find a new dentist. On the other hand, a friend from college who just got a couple of kittens after spending the last 7 years catless reported to me that the nutrition advice she got from her shiny new vet was startlingly different from what she was used to hearing. It was also much more in line with what I know. When she asked me about it, I was able to confirm and elaborate rather than contradict and re-teach.
As I understand it, even in humans with renal failure they are starting to realize that going low protein too soon in the course of the disease undermines general health and leads to greater weakness overall. And naturally not all doctors have caught up. With cats, as I understand it, since they are obligate carnivores, they are designed to thrive on eating prey animals and their digestive systems are not designed to handle plant-based foods. So it is even more perilous to start a cat in renal failure on a low protein diet too soon. Which diet leads to one's elimation systems dealing with fewer toxins: nutrient-dense food that satisfies one's needs with a relatively small amount of food; or food diluted with fillers that causes one to eat more in order to meed the body's needs and ultimately causes other health problems due to the poor quality?
When Harvey first had struvite crystals in his urine, I was still feeding him Purina. I followed the vet's advice to start him on whatever Hill's Prescription food. That was higher quality food. So he ate less and was generally healthier. But it was not until I learned enough about feline nutrition to suspect Harvey had some food allergies, and so switched him to the Iams low-pH and then learned enough to be unsatisfied with that quality that I rebelled against veterinary advice. I started feeding him half Iams Veterinary food, and half even higher quality foods such as Merrick, Natural Balance, Evo, Nature's Variety, etc. I also flat-out refused any suggestions to re-introduce dry food to his diet. He got even healthier. Then when Iams changed their formula to include fish, I dug my heels in and refused to feed it to Harvey any more. We went a few rounds with medication to acidify his urine, but it made him nauseated. When we retested his urine to see just how necessary the medication was, it turned out he was doing just fine on the better foods with no need for medication. And on these quaity foods, he eats even less. One 5.5 oz can feeds both cats for a day.
FLUTD is not the same as renal failure. I know I would have to think long and hard before defying veterinary advice in that event. But I think I would hold out until the end stages before switching to a low protein diet.