Provided are a method for promoting insulin secretion, a method for suppressing the elevation of a blood glucose level, a method for ameliorating diabetes mellitus, a method for promoting growth of an animal, and a method for increasing an insulin level in breast milk. These methods comprising administering at least one member selected from the group consisting of a di- or a higher saccharide containing galactose, a derivative thereof, a saccharide containing N-acetylneuraminic acid, and a derivative thereof, to a patient in need thereof or an animal.