Abstract: Compositions containing human milk proteins, including the so-called host resistance factors of human milk, prepared by chemically synthesizing the human milk proteins or by genetic engineering techniques for producing recombinant human milk proteins, are useful for supplementing or enhancing the diet of infants, particularly very-low-birth-weight infants. The human milk proteins include the host resistance factors (HRF) found in human milk, such as lactoferrin (LF), lactoperoxidase (LP), lysozyme (LZ), immunoglobulin-A (IgA), alpha-lactalbumin, alpha, beta, kappa-caseins, and others. The compositions may also include components other than the human milk proteins useful for improved infant nutrition. In the utilization of the compositions of this invention, the compositions would be administered to an infant in at least an amount that the infant would receive if fed substantially only fresh human milk.