A METHOD FOR SCREENING FOR A FOODSTUFF PROVIDING PRODUCTION OF MILK HAVING AN IMMUNOREGULATORY ACTION, A NOVEL FOODSTUFF HAVING AN IMMUNOREGULATORY ACTION, AND A METHOD FOR PRODUCING IT ARE PROVIDED. A DIET OR SUBSTANCE THAT INCREASES OR DECREASES AN AMOUNT OF MICRORNA PRESENT IN MILK OF A MAMMAL IS IDENTIFIED BY USING CORRELATION OF MICRORNA PROFILES IN THE MILK AND A DIET AS AN INDEX TO SCREEN FOR A DIET OR A SUBSTANCE PROVIDING PRODUCTION OF BREAST MILK HAVING AN IMMUNOREGULATORY ACTION. FIG. 1