Intestinal mucosal defense system, Part 1. Consensus recommendations for immunonutrients.

When microbial communities colonize in the developing intestinal tract after birth, microorganisms interact with specific apical surface receptors on the enterocytes. This interaction triggers a response that prevents overexpression of inflammatory cytokines, thus providing protection from pathogen-induced mucosal damage. Multiple immune modulatory factors in human milk and innate humoral factors also control inflammatory responses, providing additional protective effects. Our understanding of the role of the luminal microbial communities or microbiota is growing rapidly as novel technologies provide new insights into their taxonomy, function during early development, and impact on life-long health. Multiple studies have evaluated the effects of the specific nutrients, glutamine, arginine, nucleotides, polyunsaturated fatty acids, and lactoferrin, on disease outcomes in premature infants. These studies support a role for nutrients to modulate host defense mechanisms in premature infants, to develop normal digestive function, to protect from bacterial translocation, and to preserve mucosal barrier integrity. These effects are clearly important. However, not enough is yet known to design specific clinical care practices that support a healthy microbiota.

Intestinal mucosal defense system, Part 2. Probiotics and prebiotics.

The interplay between microorganisms and the intestine of newborn infants is associated with diverse functional and clinical outcomes that result from the specific interactions among microbial communities, their products, and the unique characteristics of the gastrointestinal tract. Multiple mechanisms of action for infant formula ingredients with probiotic activity appear to exist. These mechanisms are thought to protect the host not only from intestinal diseases but also from systemic infection. However, questions about the safety of probiotics for preterm infants remain unanswered, particularly with regard to sepsis, immunomodulatory effects, and microbial resistance. Few well-designed studies have been conducted to evaluate the effects of probiotic, prebiotic, and synbiotic ingredients on relevant clinical outcomes in preterm infants. Although existing data are encouraging, there is insufficient evidence to recommend the routine use of these ingredients in all preterm infants.