Unlike animal based products, a plant based diet doesn't give you all of your amino acids in very many foods. There are 9 amino acids (protein building blocks) you need, but you can't make. You must get them from your food. To be able to use these protein building blocks you need to ingest all of them within a 3 day period. Knowing where to get these essential amino acids and which vegan foods contain ALL of them helps you get the protein you need for optimal health.