These peptides can either originate from natural sources, for example from soy or milk, from the design of peptide mimetics, or from peptide screens using synthetic peptides. It is thought that some of these peptides may function as modulators of the cell-cycle that regulates the production and function of proteins needed to advance cells through the replication cycle. In addition, there is now increased evidence that specific dietary pattern, foods and drinks, and other dietary substances can and do protect against cancer.