<human>:  What is the best protein powder to build muscle?
<bot>: The best protein powder to build muscle is whey protein. It is a complete protein, containing all nine essential amino acids that the body needs for optimal muscle growth. It has a high concentration of branched-chain amino acids (BCAAs), which are essential for muscle building and repair, and also contains essential fatty acids, vitamins, and minerals. Whey protein is a fast-acting protein, which helps deliver quick nutrition to muscles after a workout.