Alternative sources of protein for vegetarians include beans, lentils, chickpeas, quinoa, and various nuts and seeds. These plant-based options provide essential amino acids necessary for muscle maintenance and overall health. Incorporating dairy products like yogurt and cheese also adds protein to a vegetarian diet. Tofu and tempeh, derived from soy, are excellent sources of complete proteins. By diversifying protein sources, vegetarians can meet their protein needs and enjoy a balanced and nutritious diet.