You already know that meat, dairy products, eggs, nuts & seeds, soy, vegetables, grains, and beans are common sources of protein. What you may not know is that proteins are classified as either complete or incomplete.
Complete proteins contain adequate amounts of the nine essential amino acids where as incomplete proteins do not. Note that incomplete proteins are not inferior to complete proteins, rather each offers unique nutrient profiles and can complement each other.
Complete (animal source, excluding soy)
Meat, milk, yogurt, cheese, eggs, soy
Incomplete (plant source)
Grains, nuts, seeds, beans, vegetables
So, choosing a complete protein will maximize your amino acid requirements and simplify meal planning. On the other hand, incomplete sources can be combined to meet all essential amino acid requirements, while providing fiber and other nutrients that animal sources may not provide. Believe me, primal Man consumed tons of meat and tons of vegetation.
The goal is to meet your protein needs at every meal. Sensible protein choices from both categories equal better meal planning, and better meal planning equals SUCCESS.
Make it a great day!