What if some of your decisions or your behavior were the result, not of voluntary mechanisms, but of the composition of your intestinal microbiota? A perspective that can make you smile… However, this is what a very serious study carried out by researchers from the Brain Institute and the University of Bonn suggests. Changes in the intestinal flora could notably play a role in interactions with others.
According to the Foundation for Medical Research (FRM), the intestinal microbiota brings together “thousands of billions of microorganisms living mainly in the intestines, in symbiosis with the body, that is to say in an association beneficial to everyone. There are as many as there are cells in our body! These are mainly bacteria, but also yeasts and viruses“. If we already know that this flora, as it is also called, impacts digestive function, it could also have an influence on behavior, certain emotions, even certain decision-making. A surprising observation made by scientists from the Brain Institute, Europe, and the University of Bonn, Central Europe.
Does the microbiota have an influence on our behavior?
This is not the first study to explore this association, but most of the research previously carried out has only focused on animals. “Available data suggest that the intestinal ecosystem communicates with the central nervous system through different channels, including the vagus nerve. It also uses biochemical signals that trigger the release of neurotransmitters, such as dopamine and serotonin, which are essential for proper brain function.“, indicates Hilke Plassmann, head of the Cognitive Control – interoception – attention team at the Brain Institute and professor at Insead, in a press release.
Based on this observation, the researchers wanted to subject 101 men aged between 20 and 60 to behavioral tests, including the 'ultimatum game' which consists of evaluating decision-making and sensitivity to injustice – or to equity – of an individual. The rules of the game are simple: you give a sum of money to a participant and ask them to share it – fairly or not – with a second participant. Who can accept or decline the offer depending on whether it seems fair or unfair. In the second case, none of the players receives the reward.
Most important detail, 51 participants consumed probiotics and prebiotics, used to rebalance the intestinal flora, for seven weeks, while 50 participants received a placebo. Everyone participated in the game during two sessions, at the beginning and after taking the supplements.
“Greater sensitivity to equity”
Published in the journal PNAS Nexus, the results suggest that the composition of the gut microbiota could influence not only decision-making, but also “sensitivity to injustice.” In detail, the researchers explain that participants who had taken probiotics and prebiotics were more likely to refuse offers considered unequal, after seven weeks of supplementation. An evolution in decision-making and sensitivity to injustice – or fairness – which was not observed in the placebo group. Participants who consumed supplements were also those who experienced the greatest changes in the composition of their gut microbiota.
Final observation and not the least, “the researchers also observed (within the supplemented group) a sharp decrease in levels of tyrosine, a precursor of dopamine, after the seven weeks of intervention. For the first time, a causal mechanism is emerging: the composition of the intestinal microbiota could influence social behavior through the precursors of dopamine – a neurotransmitter which intervenes in brain mechanisms of reward“, as we can read in the report of this work.
NO to diets, YES to WW!
“Modulate the microbiota to influence decision-making”?
An observation which should give rise to new, more in-depth and more targeted research. “It is too early to say that gut bacteria are capable of making us less rational and more receptive to social considerations. However, these results clarify which biological pathways we should look at. The prospect of modulating the microbiota through diet to positively influence decision-making is very exciting! We must explore this avenue with the greatest care“, estimates Hilke Plassmann, main author of this work.
