Protein content varies significantly among different food sources. Animal products like meat, fish, dairy, and eggs generally contain higher protein levels and are considered complete proteins, meaning they provide all essential amino acids. On the other hand, plant-based sources such as beans, lentils, nuts, and grains may offer lower total protein content and often lack one or more essential amino acids, categorizing them as incomplete proteins. Combining multiple plant sources can provide a complete protein profile, crucial for individuals following a vegetarian or vegan diet.