Summary: Does the community of bacteria in your gut determine how you handle a high-pressure situation? A new study provides fresh evidence that the human gut microbiome is intrinsically linked to acute stress reactivity.
Researchers found that individuals with higher microbial diversity exhibited stronger hormonal and subjective responses to stress, a trait that may actually signal a more resilient and flexible biological system rather than a “weakness” to pressure.
Key Facts
- First of its Kind: While animal studies have long suggested this link, this is one of the first robust studies to confirm the association between gut composition and acute stress reactivity in healthy humans.
- Methodology: The team used standardized stress tests (like the Trier Social Stress Test) paired with stool sample analysis and repeated saliva collection to measure cortisol.
- Lifestyle Influence: Because diet and lifestyle directly determine microbial diversity, these factors may be the hidden “remote controls” for how we react to a bad day at work or a sudden scare.
- Future Therapy: The research suggests that targeted modulation of the microbiome, through diet or specific prebiotics, could eventually be used to help individuals with stress-related conditions.
Source: University of Vienna
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.
Key Questions Answered:
A: According to this study, it might! Higher microbial diversity was linked to stronger stress reactivity. This suggests your body is well-equipped to “turn on” its survival systems when needed. The problem usually isn’t the acute response, but the inability to “turn it off” afterward.
A: Fiber is the primary food for the bacteria that produce butyrate and propionate. While you can’t change your reaction overnight, long-term dietary shifts that increase microbial diversity could help your body regulate its stress hormones more efficiently.
A: That’s the million-dollar question. They are both “good” fatty acids, but they interact with the brain through different pathways. This complexity shows that “balancing” the gut is more important than simply boosting one single metabolite.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this stress research news
Author: Theresa Bittermann
Source: University of Vienna
Contact: Theresa Bittermann – University of Vienna
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Gut microbial diversity and inferred capacity to produce short-chain fatty acids are associated with acute stress reactivity in healthy adults” by Thomas Karner, Paul A.G. Forbes, David Berry, and Isabella C. Wagner. Neurobiology of Stress
DOI:10.1016/j.ynstr.2026.100807
Abstract
Gut microbial diversity and inferred capacity to produce short-chain fatty acids are associated with acute stress reactivity in healthy adults
Acute stress triggers the release of stress hormones such as cortisol, increasing stress reactivity and aiding post-stress recovery. Rodent studies revealed that stress reactivity is modulated by the gut microbiota, and few interventional studies have provided evidence for an effect on human cortisol dynamics.
However, it remains unclear whether stress reactivity is related to interindividual variations in gut microbial composition and to one’s capacity to produce microbial metabolites such as short-chain fatty acids (SCFAs).
To close this gap, we analyzed data from 74 healthy human adults who completed the study in the laboratory and were either exposed to a well-established, standardized intervention that induced acute stress or to a non-stressful control condition (n = 35/39 per stress/control group).
Stool samples were obtained at baseline, and the gut microbiota were characterized through 16 S rRNA gene amplicon sequencing. Cortisol changes were assessed from repeated saliva sampling, paralleled by measurements of subjectively experienced stress.
We found that higher gut microbial alpha diversity was associated with higher cortisol and subjective stress reactivity across individuals of the stress group, but not in controls.
Cortisol stress reactivity was also associated with the relative abundance of bacterial taxa inferred to encode metabolic pathways for the production of butyrate and propionate, two key SCFAs.
The results are the first to highlight the link between gut microbial diversity, inferred SCFA production capacity, and the acute stress response in healthy adults, underscoring the microbiota’s potential to flexibly modulate human psychophysiology in the aftermath of stress.
