Eating protein 30 minutes after you workout helps your body to build and maintain muscle. During your weight lifting session the muscle is actually being broken down, the muscle fibers tear under the stress causing trauma and metabolic depletion of the muscle which then causes a reaction in your body to repair and reinforce those damaged fibers. It is during the repair phase that the muscle building occurs. Remember, the first protein nutrition fact-your body uses protein to build, repair and maintain almost all of the tissue in your body, therefore, in order to increase the "profits" from your weight training you need adequate protein to repair your muscle tissue
I suggest a good quality whey protein shake. A whey protein shake will raise the amino acid levels in your body, these are the building blocks of protein. A protein powder consisting of a high percentage of milk protein isolate is the better choice because it is slow in releasing amino acids, once released the blood amino acid levels remain elevated for several hours, resulting in better protein accretion.
So...If you are going to train hard, then eat to support those efforts.
Have a great day!