A nutritional composition for improving the immunological function of a subject, including a lipid or fat; a protein source; about 5 to about 100 mg/100 kcal of a source of long chain polyunsaturated fatty acids which comprises docosahexanoic acid; and about 0.1 to about 1 mg/100 kcal of a prebiotic composition, wherein the prebiotic composition comprises at least 20% of an oligosaccharide which has a fermentation rate which is demonstrably slower than that of galacto-oligosaccharide.