The compounds formed in the intestine, including metabolic products produced by probiotics like Short Chain Fatty Acids (SCFAs) and acetolactic acid, affect brain function through a fascinating and complex network of interactions known as the gut-brain axis. Here's a brief overview of how these compounds can travel and influence the brain:

Hope this helps.

Simone

While applauding Simone's answer to your question, I wonder whether the primary influence of the microbiome is directly on the intestinal wall. After all, once absorbed into the bloodstream, SCFAs are chemically indistinguishable from those supplied by our foods. Another point is that those people who, sadly, have lost their intestine and, therefore, their intestinal microbiome, remain healthy (albeit with a stoma bag), and have a normal lifespan. Our suspicion is that the microbiome exerts its influence during the birth process, with little consequence thereafter. Allow me to draw your attention to our earlier work:

https://mdpi-res.com/d_attachment/gastrointestdisord/gastrointestdisord-04-00028/article_deploy/gastrointestdisord-04-00028.pdf?version=1667811118

or, more recently:

https://mdpi-res.com/d_attachment/gastrointestdisord/gastrointestdisord-05-00018/article_deploy/gastrointestdisord-05-00018.pdf?version=1684152184

Some light reading!

Специальный С- белок с определенной конфигурацией попадает из кишечника в кровь, затем с кровотоком в мозг, в черную субстанцию и вызывает болезнь Паркинсона.