Disclosed is an infant formula, baby food, or fortified breast milk, comprising a formulation comprising an isolated disialyllacto-N-tetraose (DSLNT) or isomer thereof and a probiotic, wherein the isolated DSLNT or isomer is free of non-DSLNT oligosaccharides and is present in the formulation at 300 μM or greater, wherein DSLNT is biologically active α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc; and wherein the isomer is any of α-Neu5Ac-(2→3)- α-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc, α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]- α -GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc, α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)- α-Gal-(1→4)-Glc, &bgr;-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc, or α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[ &bgr;-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc. Also disclosed is a formulation in the form of a tablet, caplet or powder comprising α-Neu5Ac-(2→3)- α-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc, α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]- α -GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc, α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)- α-Gal-(1→4)-Glc, &bgr;-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[α-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc, or α-Neu5Ac-(2→3)-&bgr;-Gal-(1→3)-[ &bgr;-Neu5Ac-(2→6)]-&bgr;-GlcNAc-(1→3)-&bgr;-Gal-(1→4)-Glc.