Dairy Foods Symposium: Dietary Influence on Milk Synthesis of Health- Promoting Components in Bovine and Human Milk

Human milk continues to be the “gold standard” in terms of optimal infant nutrition during the first 4 to 6 mo of life, although its composition is variable and incompletely understood. The purpose of this talk will be to highlight 3 areas of intense current research concerning human milk composition, as well as reviewing what is known about the effects of maternal diet and putative infant health outcomes. The first topic is the potential for human milk to be classified as a “symbiotic” food containing both preand probiotic constituents. Indeed, one of the most abundant components of human milk is a large and diverse group of complex carbohydrates (human milk oligosaccharides; HMO), which appear to be largely indigestible by the infant’s intestinal enzymes but which may modulate healthy development of the infant’s gastrointestinal (GI) microbes. Human milk oligosaccharides are also thought to impart health benefits via modulation of the immune system and direct interactions with pathogenic GI microbes. Some data also suggest that HMO might mediate microbial metabolism. Noteworthy, however, is the fact that the oligosaccharides currently added to some proprietary infant formulas are structurally quite different from those common in human milk; this likely has important functional health outcomes (or lack, thereof) for the recipient infant. Recent studies have also shown that human milk, even when produced by healthy women without signs or symptoms of mastitis, contains a rich and diverse community of bacteria. This finding, along with evidence that the human milk microbiome can be influenced by maternal probiotic consumption, suggests that consumption human milk might be particularly critical for establishing a healthy complement of GI microbiota during early life and that this effect may be modulated, at least in part, by maternal diet. Finally, research continues to support a strong and consistent effect of maternal diet on relative milk n-3 and n-6 fatty acid contents, although results of controlled clinical trials are mixed in terms of relating this variation to shortand long-term effects on infant health and wellbeing.