New Study Found That Gut Bacteria Can Predict One’s Personality

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Some new research has shown an interesting association between gut bacterial diversity and personality traits, such as sociability and neuroticism. These findings accentuate the potential benefits of eating foods rich in pre- and probiotics.

Katerina Johnson, Ph.D., from the Department of Experimental Psychology at Oxford University, United Kingdom, wanted to find out if there is a connection between the structure of the gut bacteria and personality traits.

She explains her reasoning for conducting the research on this topic, by saying “There has been growing research linking the gut microbiome to the brain and behavior, known as the microbiome-gut-brain axis.”

“Most research has been conducted in animals, while studies in humans have focused on the role of the gut microbiome in neuropsychiatric conditions.”

“In contrast, my key interest was to look in the general population to see how variation in the types of bacteria living in the gut may be related to personality.”

Accordingly, Johnson collected fecal samples from 655 adults, of whom 71% were female, and 29% male with an average age of 42. The scientist used 16S rRNA gene sequencing analysis to look at the abundance of specific bacterial genera.

The study also involved asking the participants to answer a comprehensive questionnaire that asked details about their behavior, health, lifestyle and sociodemographic factors.

Johnson carried out a set of statistical analyses, in order to help her team determine the association between the composition of the gut bacterial and personality and behavioral traits, like sociability and neuroticism. They have published their findings in the Human Microbiome Journal.

Gut bacteria and five personality traits

More exactly, Johnson used the International Personality Item Pool — which includes 50 items — to assess personality traits based on the “five-factor model of personality.”

By following this model, it suggests that differences in personality are grouped under five main domains, the “Big Five:”

  • extraversion, or the “propensity to seek and enjoy others’ company”
  • agreeableness, defined as “trust and cooperation in social interactions”
  • conscientiousness, or the “attention to detail and focus”
  • neuroticism, i.e., the “tendency to feel negative emotions”
  • openness, which researchers have described as “creativity, intellectual curiosity, and willingness to seek new experiences”

The researchers have applied multiple regression analyses of the bacterial taxa, adjusting for key variables that scientists know influence the structure of the gut bacteria, and that may have otherwise confounded the results.

These variables were sex, age, body mass index (BMI), birth delivery mode, infant feeding method, use of oral antibiotics in the last 6 months, gut conditions, and use of probiotic supplementation.

Johnson adjusted for these potential confounders only in a subset of 261 participants who had provided the necessary information.


More friends may promote gut health

The study also found that multiple types of bacteria that researchers had linked with an autism spectrum disorder in some past research was also connected with sociability differences in the general population.

“This suggests that the gut microbiome may contribute not only to the extreme behavioral traits seen in autism but also to variation in social behavior in the general population,” explains Johnson.

Additionally, the study discovered that people with more extensive social connections were more prone to have a more diverse composition of gut bacteria. This means that being socially active may promote the diversity of the gut microbiome.

Moreover, many people believe that greater diversity in the human gut microbiome contributes to gut health and better overall health.

“This is the first study to find a link between sociability and microbiome diversity in humans and follows on from similar findings in primates, which have shown that social interactions can promote gut microbiome diversity. This result suggests the same may also be true in human populations.” – Katerina Johnson

As an alternative, the analysis discovered that lower microbial diversity was associated with higher stress levels and anxiety.

The importance of nutrition

In addition, an intercorrelation analysis “revealed that people who ate more foods with naturally occurring probiotics or prebiotics had significantly lower levels of anxiety, stress, and neuroticism and were also less likely to [develop] a mental illness.”

However, the researchers didn’t find the same connection between probiotics or prebiotics found in supplement form.
Some natural sources of probiotics are: fermented cheese, sauerkraut, kimchi, and natural sources of prebiotics include bananas, legumes, whole grains, asparagus, onion, and leek.

Another bizarre finding was that people who had been fed formula as babies had less diverse gut microbiome.

“This is the first time this has been investigated in adults, and the results suggest that infant nutrition may have long-term consequences for gut health,” says Johnson.

“Our modern-day living may provide a perfect storm for dysbiosis [i.e., an imbalance in the microbiota] of the gut,” adds Johnson.

“We lead stressful lives with fewer social interactions and less time spent with nature; our diets are typically deficient in fiber, we inhabit over-sanitized environments and are dependent on antibiotic treatments.” – Katerina Johnson

Katerina Johnson, however, acknowledges a limitation of her research. She says, “since this is a cross-sectional study, future research may benefit from directly investigating the potential effect these bacteria may have on behavior, which may help inform the development of new therapies for autism and depression.”

“All these factors can influence the gut microbiome and so it may be affecting our behavior and psychological well-being is currently unknown ways.”

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