The disclosure relates to a new crystalline form of genistein. The disclosed crystalline form is crystalline genistein sodium salt dihydrate. The disclosure also relates to the novel genistein salt composition represented by this crystalline form. Therapeutic compositions containing crystalline genistein sodium salt and a pharmaceutically acceptable carrier are described. The disclosure also relates to therapeutic methods comprising the step of administering to a patient in need thereof a therapeutically effective amount of a therapeutic composition containing the crystalline form of the disclosure or crystalline genistein sodium salt dihydrate.