A non-therapeutic method of providing a nutritional composition comprising HMOs to a pediatric subject, the method comprising: determining the composition of HMOs that are present in or would be present in the breast milk of the mother of the pediatric subject as determined by the mother's secretor status and/or Lewis blood group, and providing to the pediatric subject a nutritional composition comprising an HMO profile most similar to the composition of HMOs as determined in step, wherein: (a) when the pediatric subject's mother is determined to have blood type Le(a+ b-) and/or the subject's mother's breast milk is determined to contain HMOs having α1-3, and α1-4-linked fucosyl residues, but determined to lack HMOs having α1-2-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 60-80% of the HMOs are sialylated, about 0-20% are fucosylated, and about 10-30% are neither sialylated or fucosylated; (b) when the pediatric subject's mother is determined to have blood type Le(a- b+) and/or the subject's mother's breast milk is determined to contain HMOs having α1-2, α1-3 and α1-4-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 20-40% of the HMOs are sialylated, about 40-60% are fucosylated, and about 10-30% are neither sialylated or fucosylated; and (c) when the pediatric subject's mother is determined to have blood type Le(a- b-) and/or the subject's mother's breast milk is determined to contain HMOs having α1-2 and α1-3-linked fucosyl residues, but determined to lack HMOs having α1-4-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 10-30% of the HMOs are sialylated, about 10-30% are fucosylated, and about 50-70% are neither sialylated or fucosylated. determining the composition of HMOs that are present in or would be present in the breast milk of the mother of the pediatric subject as determined by the mother's secretor status and/or Lewis blood group, and providing to the pediatric subject a nutritional composition comprising an HMO profile most similar to the composition of HMOs as determined in step, wherein: (a) when the pediatric subject's mother is determined to have blood type Le(a+ b-) and/or the subject's mother's breast milk is determined to contain HMOs having α1-3, and α1-4-linked fucosyl residues, but determined to lack HMOs having α1-2-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 60-80% of the HMOs are sialylated, about 0-20% are fucosylated, and about 10-30% are neither sialylated or fucosylated; (b) when the pediatric subject's mother is determined to have blood type Le(a- b+) and/or the subject's mother's breast milk is determined to contain HMOs having α1-2, α1-3 and α1-4-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 20-40% of the HMOs are sialylated, about 40-60% are fucosylated, and about 10-30% are neither sialylated or fucosylated; and (c) when the pediatric subject's mother is determined to have blood type Le(a- b-) and/or the subject's mother's breast milk is determined to contain HMOs having α1-2 and α1-3-linked fucosyl residues, but determined to lack HMOs having α1-4-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 10-30% of the HMOs are sialylated, about 10-30% are fucosylated, and about 50-70% are neither sialylated or fucosylated. (a) when the pediatric subject's mother is determined to have blood type Le(a+ b-) and/or the subject's mother's breast milk is determined to contain HMOs having α1-3, and α1-4-linked fucosyl residues, but determined to lack HMOs having α1-2-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 60-80% of the HMOs are sialylated, about 0-20% are fucosylated, and about 10-30% are neither sialylated or fucosylated; (b) when the pediatric subject's mother is determined to have blood type Le(a- b+) and/or the subject's mother's breast milk is determined to contain HMOs having α1-2, α1-3 and α1-4-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 20-40% of the HMOs are sialylated, about 40-60% are fucosylated, and about 10-30% are neither sialylated or fucosylated; and (c) when the pediatric subject's mother is determined to have blood type Le(a- b-) and/or the subject's mother's breast milk is determined to contain HMOs having α1-2 and α1-3-linked fucosyl residues, but determined to lack HMOs having α1-4-linked fucosyl residues, the nutritional composition provided to the pediatric subject comprises an HMO profile wherein about 10-30% of the HMOs are sialylated, about 10-30% are fucosylated, and about 50-70% are neither sialylated or fucosylated.