A team of investigators from the University of Rouen France, the Georgia State University Atlanta, Georgia and Bio-Rad have proposed that the gut bacteria and the human nervous system interact to determine food preference ( presented in the Journal of Bacteriology). The bacteria produce chemical signals called neuroendocrines that are transmitted first to local intestinal nervous system and then to the central nervous system (the brain). The bacteria which want particular food suggest the host of their food preference “menu.” The host becomes a matre d or menu server.
The enteric nervous system forms an independent nervous loop, and is sometimes referred to as the second brain. The intestinal wall has embedded nervous system made up of about 500 million neurons which carry signals to the brain and back, a network connecting the local neurons ( these are nerve cells that use electrical and chemicals forms tor transfer of information), and over 30 neurotransmitters (chemical signals) including acetylcholine, dopamine, and serotonin. The microorganisms also possess homologous neurohormones, neurotransmitters and their receptors – including corticotropin, somatostatin, and ?-aminobutyric acid (GABA).
Then there are star like nervous cells, the nervous cell complex called ganglia surrounded by the blood capillaries with protective coating as diffusion barrier (blood-brain barrier). This system independently controls gastric acid, secretion, intestinal motility, local blood flow, flow of fluid and nutrients across the epithelium lining, and interacts with the endocrine and immune systems of the gut.
The scientists propose that there appears to be communication between the host and the bacteria. The bacteria inform the host about the food they require to survive. While the food and frequency of eating as well as the stress which the host undergoes determines the bacterial population of the gut. The research team thus proposes that there is “Dependence of bacterial composition on human behavior”. The type of bacterial population in the gut, depends on large extent by the food consumed by the host, and by the stresses to which the host is subjected. On the other hand “Bacteria Influence Host Appetite”. The bacteria in the gut influence the physiology and host behavior, in particular the preferences of their hosts for certain nutrients.