Wednesday, June 08, 2016
Human host - gut microbiota complex ecosystem depends on dietary nutrients
Human hosts and gut microbiota share a relationship that may range from mutually beneficial to parasitic in nature. Microbes may confer benefits on their hosts by producing energy and vitamins, and fostering a local environment that is unfavourable to other pathogens.
Human hosts, on the other hand, provide resources for microbes and help maintain the microbial habitat. The interaction between the human host and the complex microbial ecosystem in the gut begins at birth, with the transfer of pioneer species from mothers to neonates.
Furthermore, breastfeeding provides naturally selected carbohydrates that support mutualist microbes, such as Bifidobacteria and Lactobacilli. Such microbes convert complex milk carbohydrates into a digestible form through fermentation to produce absorbable energy in the form of short-chain fatty acids.
The lipid fraction of breast milk gets converted to antimicrobial fatty acids that discourage the growth of harmful pathogens. Microbes also help in digestion of the dietary fibre; this unlocks the energy that is inaccessible to the human host without microbial fermentation. However, the iron required for bacterial metabolism is attached to lactoferrin in breast milk. Consequently, the low-iron environment favours the growth of mutualist microbes.
Dietary components such as certain sugars and fats may accelerate the growth of pathogens. The modern Western diet is high in simple sugars and saturated fats, which may contribute to an escalation of the conflict between hosts and gut microbes, resulting in a greater degree of intestinal parasitism. Local changes to the gut environment may contribute to the development of chronic inflammatory disorders.
A better understanding of the mechanisms of cooperation and conflict between human hosts and microbes can facilitate the development of novel interventions with potential benefits to the human gut and health.
News Source: Wasielewski H, Alcock J, Aktipis A. Resource conflict and cooperation between human host and gut microbiota: implications for nutrition and health. Annals of the New York Academy of Sciences. 2016 June.