Whey protein is derived from milk (and therefore classified as an animal protein). It is a complete protein in that it contains all the essential amino acids needed to sustain all the body functions we need. When taken within 30 minutes after working out, it is the protein that the body absorbs the fastest which means that your body can start using it to replenish the proteins the muscles have used up and recover, repair and build muscle right when it needs it most.
Soy protein is derived from soybeans (and therefore classified as a plant-protein). It is an incomplete protein in that it does not contain enough of all the essential amino acids your body needs to function, but more importantly, to replenish/recover from workouts. Your body will have to find those amino acids in other ways (from food consumed or breaking down unused muscles). For example, it is low in “methionine” which helps with metabolic processes, breaks down fat, and helps the body remove heavy metals. Soy protein, on the other hand, contains hidden proteins (isoflavones) that can mimic the activity of estrogen in the body, particularly beneficial for pre and peri-menopausal conditions. Additionally, the body does not absorb soy as quick as whey, but that is not a bad thing. Soy takes a little longer to be digested so it takes more time to provide the same amount of amino acids as whey. However, the level of amino acids
is sustained over a longer period (think “slow release”) so you feel fuller longer – often used by individuals looking to manage their weight.