As your cat ages, its diet must change to suit its changing health conditions. Metabolism, eyesight, and kidney function are important to take into account for a mature cat's diet. The food you buy for your cat should reflect all of these concerns.
Finding the right food is a continuous process as your cat's needs change with their life stages, and it's up to you to fulfill those needs. While it is encouraged to be involved and practical about your cat's diet, giving them homemade cat food or treats should be avoided due to the complex dietary requirements in cat food.