The present invention relates to a pharmaceutical composition including: a pharmaceutically effective amount of at least one peptide； and a pharmaceutically acceptable amount of a combination of: (a) at least one metal in form of any or a combination of a salt thereof and a complex thereof； and (b) at least one reducing agent, wherein, the at least one metal is selected from any or a combination of: vanadium, chromium and manganese, and wherein the combination of (a) at least one metal in form of any or a combination of a salt and a complex and (b) at least one reducing agent affords protection, at least in part, to the at least one peptide from proteolytic degradation upon ingestion thereof.
