The composition of our intestinal flora also influences our behavior and, according to a recent study, taking certain probiotics can increase our sensitivity to fairness. The intestinal bacteria apparently control our decision-making.
A research team from the Sorbonne Université and the University of Bonn tested the effects of taking nutritional supplements containing Lactobacillus and Bifidobacterium on so-called altruistic social punishment behavior. The surprising results are published in the specialist magazine “PNAS Nexus”.
Do intestinal bacteria influence our behavior?
There is increasing evidence for the role of gut flora in regulating socio-affective behavior, but it has remained unclear whether and how the composition of the gut microbiome can influence social decision-making, the team explains.
The researchers have now examined the effect of a seven-week nutritional intervention with Lactobacillus and Bifidobacterium nutritional supplements on decision-making in an ultimatum game in 101 participants (51 experimental group, 50 control group).
Increased sense of fairness
Compared to taking a placebo, the intervention with the probiotics increased the participants' willingness to forego a monetary reward if they were treated unfairly in the game, the researchers report. Her sense of fairness appears to have increased.
According to the experts, this change in social decision-making was linked to changes in fasting serum levels of the dopamine precursor tyrosine, suggesting a possible mechanical connection along the gut-brain axis.
The supplements reduced plasma tyrosine levels in some participants, and those who experienced this reduction experienced the most significant increase in altruistic punishment, the research team continued.
In addition, the greatest changes in both the composition of the intestinal flora and the frequency of altruistic punishment were observed in participants who had a high ratio of Firmicutes to Bacteroidetes at the beginning of the study.
Less rational, but more social
According to the researchers, the changes towards healthier intestinal flora led the participants to become less rational and more sensitive to social considerations.
Overall, a better understanding of the interactions between gut flora, the brain and social decision-making could also help to explain our supposedly “irrational” behavior in some situations.
First indications of a connection
However, science has only just begun to unravel the importance of the human gut microbiome for our behavior. The new study provided the first clear evidence of a potential influence on the extent of altruistic punishment and decision-making. (fp)
