One of the sub-areas of microbiome research focuses on the communication of the bacteria in the gut with the central nervous system and the immune system. Substances produced in the gut by bacteria are at the origin of neurological, hormonal and immunological processes.
It’s challenging thoughts that what we eat, and the millions of critters that produce poop from it, make important ‘decisions’ about mental health.
The brain in the gut
‘The brain in the gut’ is the name of the neurobiological activity in the gut. Little by little, this ‘second brain’ begins to reveal its deepest secrets. Research at the molecular level uncovers the connections between the substances that the intestines make from food, and those that later – once admitted to the body through the intestinal wall – influence metabolic regulation, neurological processes and mood in the brain. .
The actual ‘brain’ part of that second brain is called enteric nervous system (TO US).
It enteric nervous system consists of a double layer of more than 100 million nerve cells in the intestinal wall and runs from the esophagus to the rectum.
The ENS works autonomously, separate from the brain in the head, but whether it can also think, conduct coalition negotiations or design the iPhone 14 is questionable. However, it controls the absorption of nutrients through the intestinal wall, regulates bowel movements, and influences the local blood supply. It should be clear that a healthy intestinal wall, which is nourished and maintained by the intestinal contents (and therefore in fact from the outside), is essential.
The interplay between the neurological centers above and below in the body inspired not only scientists, but also fanatics and quacks
Just under ten years ago, the ENS was in the spotlight because people with chronic inflammatory bowel disease also sometimes had psychological problems and a link was suspected. New techniques showed that the neurons in inflamed areas did not work properly. The signaling by the neurons is disrupted by what is called ‘functional dyspepsia’, a collective term for abdominal pain, already thirty years ago described for general practitioners, but still a vague diagnosis.
In addition to pain and discomfort, patients with irritable bowel syndrome (PDS) sometimes emotional and even depressive complaints. There seemed to be an interaction, a permanent feedback or mutual influence, an interplay of the hormonal, neurological and immune system.
These psychological complaints are difficult to distinguish from the emotional burden that the disease itself already entails. Constant abdominal pain, diarrhea and other discomfort do not make you a happier and more sociable person. IBD patients, who suffer from the serious chronic inflammatory diseases Ulcerative Colitis and Crohn’s, often have a hard life.
A name came up for the second brain, the neuroendocrine immune pathway, or neuroendocrine-immune pathway, IN THE.
Taking antidepressants helped some IBS patients reduce their intestinal problems, which indicated a feedback loop. The interaction between the neurological centers above and below in the body not only inspired scientists, but also fantasists and quacks.
The question with these kinds of observed phenomena is always: what are the mechanisms? What are the pathways of control at the cellular and molecular level? Only when these have been demonstrated, there is solid evidence, until then we have to make do with indications, suspicions or other non-causal forms of relationship.
A number of substances are known to contribute to a healthy intestinal wall, such as short-chain fatty acids and secondary bile acids, both of which are formed by bacterial action. One by digestion of dietary fiber, the other by conversion of bile from the liver. Research into these metabolites has yielded an important new discovery, according to researchers from the Universities of Bath (UK) and Massachusetts (US), namely “the protein that lets the gut talk to the immune system.”
That protein, P-glycoprotein, is a known transport protein, which acts as a pump to get substances in and out of cells. It is also present in large amounts in the cells of the intestinal wall. The intestinal wall is a highly selective sieve, whose task is to allow beneficial substances, such as nutrients, to pass into the bloodstream and to stop toxins. If the latter no longer functions properly, there is a leaky gut.
It now also appears, according to the researchers in their items in the trade magazine Microbiome, that P-gp has a signaling function, instructing the immune system to maintain homeostasis in the gut: the healthy, balanced ‘internal environment’. This prevents low-grade inflammation, the root cause of many ailments, including intestinal disease.
“For the first time, we show an example of two classes of metabolites, short-chain fatty acids and secondary bile acids, that work together to regulate gut wall function,” they conclude. It proves the importance of a fiber diet for gut bacteria to produce the short-chain fatty acids. But what nutrients are needed to optimize P-gp production, thereby helping the immune system to regulate inflammation, is not clear from this study.
The researchers also draw a more general conclusion. A greater diversity of the microbiome, with a richer variety of types of bacteria, provides a better guarantee for the adequate production of the required metabolites. More types of bacteria can produce the same types of fatty acids. This wealth of fatty acids and other metabolites protects a healthy intestinal wall, and thus body and mind.
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Healthy bowel function counteracts depression – Harder evidence: food with fiber influences physical and psyche – Foodlog