Many cats have cravings, which are defined as a desire to eat certain substances--some of which may be classified as food (for example, shrimp) and others (such as leather or plastic) perhaps not. Many people may think cats crave certain items because of a nutritional deficiency, but this is simply not the case. Cats, like humans, will more often eat what they like, not what they need. If you are feeding your cat food that is complete and balanced, and if it's eating sufficient quantities of it, your cat should be getting all the nutrients it needs. The complete and balanced commercial foods should constitute 85 to 90 percent of your cat's total food intake.