The gut microbiome influences numerous physiological processes. Researchers at the University of Vienna have now demonstrated for the first time that, in healthy adults, the diversity of gut bacteria and their capacity to produce certain metabolites are associated with the acute stress response - particularly stress reactivity. Higher microbial diversity was associated with stronger hormonal and subjectively perceived stress reactivity. The results suggest that the gut microbiome may play a role in regulating the acute stress response. The study was published in Neurobiology of Stress.

The gut microbiome comprises all microorganisms living in the gut, which, among other things, perform important functions in metabolism and the immune system and are also connected to the brain through various pathways. Research suggests they can modulate the stress response. However, it has remained unclear until now whether differences in the human gut microbiome are actually associated with acute stress reactivity.

The latest findings by researchers Thomas Karner, Isabella Wagner, David Berry, and Paul Forbes from the Faculty of Psychology and the Center for Microbiology and Environmental Systems Sciences (CeMESS) at the University of Vienna provide new evidence that the gut microbiome, and thus potentially also diet and lifestyle, is associated with how our bodies respond to stress. In the long term, targeted modulation of gut microbial composition and its metabolites, particularly short-chain fatty acids, could represent a possible avenue for new strategies to related to acute stress responses, stress-related conditions and improve well-being.

Stress tests, saliva samples, and more provide insight into the association

In the study, healthy participants either underwent a standardized stress test or performed a comparable, stress-free task. Stress hormones (cortisol) in saliva and subjective stress levels were measured. In addition, the gut microbiome was analyzed using stool samples. Both the composition of the microbiome and the estimated production capacity of short-chain fatty acids were examined. The results show that higher microbial diversity was associated with higher hormonal and subjective stress reactivity. Greater microbial diversity is often associated with a more stable and resilient microbial ecosystem and with greater functional flexibility, which may contribute to the appropriate regulation of stress responses.

"A stronger acute stress response is not necessarily detrimental. Appropriate activation of the stress system enables flexible adaptation to challenges and threats. A greater diversity of gut bacteria, as well as certain metabolic products, could play a supportive role in this process," explains study leader and psychologist Thomas Karner.

Complex relationship between microbial metabolites and stress reactivity

Furthermore, stress reactivity was associated with gut bacteria’s capacity to produce different metabolic products: a higher estimated capacity for butyrate production was associated with higher stress reactivity, whereas higher propionate production was associated with lower reactivity. Butyrate and propionate are short-chain fatty acids produced by gut bacteria that are involved in metabolic and immune processes and can also affect the brain. This suggests that the relationship between microbial metabolites and the acute stress response is more complex and cannot be reduced to a single direction.

The results provide new insights into possible biological mechanisms of stress regulation and underscore the role of the gut microbiome and its metabolites as potential factors influencing the stress system and the acute stress response in humans.

Summary:

• Higher gut microbial diversity is associated with higher hormonal and subjective stress reactivity in healthy adults
• Estimated capacity for short-chain fatty acid production is associated with hormonal stress reactivity. Higher butyrate production is associated with higher stress reactivity, while higher propionate production is associated with lower stress reactivity
• The findings demonstrate an association between the gut microbiome and acute stress, as well as the possible role of the gut microbiome as a factor influencing the stress system
• In the long term, changes in the gut microbiome and its metabolites, for example, through diet or targeted interventions, could represent a possible approach to influencing stress responses and stress-related conditions

About the University of Vienna:

At the University of Vienna, curiosity has been the core principle of academic life for more than 650 years. For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected. With degree programmes covering over 180 disciplines, and more than 10,000 employees we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.

You can find out more about stress here in the special feature Don't stress! in the University of Vienna’s science magazine Rudolphina.