The expression of heterologous peptides or polypeptides in the seeds of monocot plants is optimized by generating fusion protein constructs in which monocot plant seed storage proteins are used as fusion protein carriers for the heterologous peptides or polypeptides. The heterologous peptides or polypeptides are preferably small, about 10 kDa or less and/or between 5 and 100 amino acids in length. These heterologous peptides or polypeptides may be used in human and animal nutritional and therapeutic compositions.