The present invention relates to a pharmaceutical or dietary composition comprising deoxyuridine and a pharmaceutically or dietetically suitable carrier. Another aspect of the present invention relates to a method of supplementing the dietary needs of a subject. This method includes administering to the subject a dietary supplementing effective amount of deoxyuridine. Yet another aspect of the present invention relates to a method of treating cancer in a subject. This method includes selecting a subject having cancer and administering to the selected subject a therapeutically effective amount of uridine, thereby treating the cancer in the selected subject.