Dietary sources rich in protein for muscle building include lean meats, fish, eggs, dairy products, legumes, and plant-based proteins such as tofu and quinoa. Animal proteins, like chicken, turkey, and fish, offer complete proteins containing all essential amino acids necessary for muscle repair and growth. Plant-based sources can also provide adequate protein and are beneficial for those seeking vegetarian or vegan options. For optimal muscle gains, individuals should aim to consume a combination of these protein sources, ideally around 20-30 grams of protein per meal.