I don’t know how Royal Canin Renal Support food works, all I know is that our cat, who was failing badly a month ago, is now doing great! He was sick, so very sick, that in fact there was a teary farewell one night when we thought he had to be euthanized. The vet told us Mr. Big had renal failure, and we should try your new line of food. He started eating the next day! What a change over the past three weeks – before, he wouldn’t clean himself, he could hardly walk, and had no joy. Now? He's still old, of course, but he is active, running – running! – and jumping, and his fur is shiny. What a turnaround from the ailing, staggering, listless pet we had just three weeks ago! I am so glad the veterinarian recommended your food.