Good nutrition means eating a balanced, healthy diet. A healthy diet includes several nutrients. These are good materials that your body gets from food. Your body contains more water than anything else.
Water is the most important nutrient.
Each cell in your body needs it. You would die a lot sooner from lack of water than from lack of food. It cools your body when you sweat. If you eat a well balanced diet with a wide variety of foods, you don't need to worry about protein. Protein can come from both animals and plants.