I have recently read this article and it was well discussed how scientists keep discovering new interesting and important facts about our gastrointestinal tract and its effect on our wellbeing (including decision making and brain function).
For example, it has been shown that if people eat more galactooligosaccharide, the fraction of bacteria Lactobacillus and Bifidobacteria in the gut increases among all other strains (because metabolism of these bacteria takes advantage of the excess of this chemical, a known prebiotic). At the same time, these particular strains of bacteria have been shown to produce certain neurotransmitters — chemicals that participate in our brain functioning (because neurotransmitters are responsible for the transmission of electrical signals between neurons). It is indeed possible that by eating certain types of food you can overproduce certain neurotransmitters and, therefore, influence your brain functioning — through bacteria in the gut (Figure 1).
What is even cooler, some bacteria have shown to affect people’s mood (possibly, by increasing production of “happiness hormones”, in other words, chemicals responsible for our social behavior). This is reasonable because happy people are more social which leads to a big evolutionary advance for these bacteria: they would obviously tend to spread better between social humans than between loners. Interesting, isn’t it?
Let’s now think about it in an evolutionary context. Do bacteria in the gut understand that they change the social behavior of their hosts? The answer is – NO. They not only don’t know anything about social behavior, but they also don’t know that they have a host and even that they exist! Bacteria are simply self-sustaining chemical reactions capable of changing (mutating) their chemical dynamics. It is not that bacteria have goals to survive, they simply occur. One random mutation in their genome led to the overexpression of a random chemical which, by a myriad of other complicated chemical transformations led to the increase of a random neurotransmitter which, by accident, tended to affect social behavior of their hosts. Now, the bacteria have started to spread faster and still spread “happily” because these chemical dynamics help them to exist or, simply, to occur.
We, humans, are chemical reactions too. All hopes and dreams in our brains are interactions between atoms, molecules and their collections. We just tend to occur because it is evolutionary logical. Our mood is chemistry too: serotonin is happiness, dopamine is pleasure, noradrenaline is concentration (Figure 2).
So, if all of this is chemistry, then how to study this? Are there techniques that would allow us to investigate gut microbiome and its effect on the brain non-invasively and in real time?
I believe the answer is yes. Non-invasive techniques like NMR and MRI will soon be able to help to answer important questions about gut metabolism with hyperpolarization being one of the main tools to achieve this. The main challenge – fast decay of polarization – will be overcome by using nuclear states that can preserve their “memory” on a timescale of hours. Remarkably, there are already reports on the long-lived hyperpolarized nuclear spin states [2-4]! Long-live the gut! 😉
 “When Gut Bacteria Change Brain Function” by David Kohn.