Modulating the gut microbiota has emerged as a means of affecting the central nervous system function and, thus, human behavior, especially in the context of stress, mood and anxiety disorders and even neurocognitive disorders. Clinical studies with probiotics using neuroimaging methods have started exploring the benefits of probiotics in the human brain. Among them, the probiotic Bifidobacterium longum 1714 has been shown to reduce stress-related behaviors and improve stress responses and cognitive function in mice and healthy volunteers, respectively. However, the mechanisms by which this probiotic influences brain function and human behavior are unclear.
A new randomized, double-blinded, placebo-controlled trial, which I led with a team of researchers from the University of Tübingen (Germany), reveals that B. longum 1714 may reduce stress responses in healthy volunteers by modulating the brain regions involved in emotional regulation.
The researchers tested the effects of B. longum 1714 at a dose of 1 x 109 colony forming units/day for 4 weeks on neural responses to social stress in a sample of 20 healthy adult volunteers (intervention group) compared with 20 controls (placebo group). Social stress was induced by social exclusion through a computerized ball game called “Cyberball game”. Magnetoencephalography (MEG) was used for measuring brain activity under social stress, whereas health status was measured with a 36-item short-form health survey.
Changes in neural activities during the resting state were observed after the intervention for participants in the probiotic group vs placebo. In addition, participants in the probiotic group showed unique correlations between the alteration in resting brain activity and increased subjective vitality. Considering previous findings that mental fatigue causes enhancement of the right prefrontal cortex, the current findings suggest that the role of B. longum 1714 in managing stress might be related to enhanced vitality and reduced mental fatigue.
Both groups reported increased changes in subjective stress scores after the 4-week intervention, which might be due to the low sample size.
However, only B. longum 1714 led to a difference in the changes in neural activity in brain areas that might be involved in the counterregulation of negative emotions in response to a social stressor. Furthermore, changes in neural activity under social stress induced by B. longum 1714 were correlated with changes in distress levels reported by questionnaire. Changes in participants’ neurophysiology due to the probiotic is a new finding, because previous research has only shown its role in improving stress responses and behavior.
In conclusion, for the first time, this study shows the role of B. longum 1714 in modulating brain function in response to social stress.
Next steps with this novel probiotic include exploring its role in other central nervous system functions in both healthy controls and patients with psychiatric, neurological and gastrointestinal disorders. Using standardized neuroimaging methods and correlating the brain data with changes in the gut microbiota at composition and functional level will help elucidate the contribution of B. longum 1714 and other probiotics to mental health.
Wang H, Braun C, Murphy EF, Enck P. Bifidobacterium longum 1714TM strain modulates brain activity of healthy volunteers during social stress. Am J Gastroenterol. 2019. doi: 10.14309/ajg.0000000000000203.