Is Soy Protein Powder a complete protein?

Soy protein powder is the only sufficiently complete plant-based protein powder. It contains all 9 of the essential amino acids your body cant make itself and are needed for correct body function. It is worth noting however that it is fairly low in methionine which is an important amino acid for muscle development. For this reason some soy protein powders also included added methionine for make up for the shortfall.