Methionine is an essential amino acid that cannot be produced by the body and is crucial for your cat's health. Because cats are obligate carnivores and meant to consume small prey, we’ve based the nutrient profile of our Young Again cat foods on a juvenile mouse. The mouse is made up of high levels of methionine. We use just enough methionine to balance the amino acid profile of our foods to duplicate the mouse model. The typical mouse is 52-58% protein, 22-28% fat and 3-6% starch. Compared to most other cat foods sold today, Young Again is higher in protein and much lower in starch/carbohydrates. And because Young Again cat foods are nutritionally-balanced, your cat will naturally maintain a healthy urine pH of 6.5 making it less likely struvite crystals or calcium oxalate stones will develop.