Phenylalanine is one of the essential amino acids, the building blocks of protein. Amino acids play a role in supporting normal growth and development in the body.. Take one tablet daily, preferably with a meal. Do not exceed stated dose. Amino acids are the main constituents of protein. There are twelve amino acids that can be made by the body, however there are another eight amino acids that are essential, meaning that they must be supplied by the diet. An amino acid complex supplement could help to maintain an anabolic state making them valuable for use in athletes and bodybuilders.