This volume presents recent findings on the role of the intestinal microflora in human health and explores the use of probiotic food supplements and other nutritional interventions aimed at modulating the intestinal flora. The contributors discuss the characteristics of the intestinal microflora, the interactions of these organisms with the immune system, and the establishment of normal intestinal flora in the neonate. Several studies examine the effects of human breast milk, lactoferrin, iron, and nucleotides on microbial flora in infants. Particular attention is given to the benefits of feeding probiotics, i.e., specific organisms such as lactobacilli and bifidobacteria. Chapters review clinical studies of probiotic agents and present clinical evidence that probiotics enhance the natural immunity of the gut. The safety of these agents is also assessed. Other nutritional strategies explored include ingestion of sugars that promote intestinal colonization with these organism.