Demanding workloads, financial pressures, home-life responsibilities and global issues that feel only too close to home. These factors are all likely contributing to recent figures, showing that a staggering 74% of adults have felt so stressed in the past year that they were overwhelmed or unable to cope (1). And this burden is not shared equally. In this same survey, 81% of women report reaching this level of stress compared with 67% of men (1).
We often treat stress as something happening purely in the mind. But science is telling a more connected story. Increasingly, researchers are looking at the gut microbiome as a key player in how we experience and recover from stress. This area of research is known as the gut-brain axis.
What is the gut-brain axis?
Your gut and brain are in constant conversation. Signals travel back and forth through the vagus nerve, hormones, immune pathways, and chemical messengers circulating in the bloodstream (2). This two-way communication means that what happens in one system quickly affects the other.
In many ways, this idea is already familiar to us. We talk about having a “gut feeling” when we make decisions based on intuition. We feel “gutted” after bad news. Nervousness brings “butterflies” to the stomach. These expressions exist for a reason. Our emotional and gastrointestinal systems are closely linked, even if healthcare has traditionally treated them separately.
Key to this relationship is the gut microbiome. Your gut is home to trillions of microorganisms, including bacteria, fungi, archaea, and viruses, which live in your gastrointestinal tract. Research shows that a healthy gut microbiome supports several aspects of brain function, including how we experience anxiety, stress, and mood, as well as how we interact socially with others (3). Our gut microbes have also been linked to sleep quality, focus, and memory decline as we age (4). Importantly, the gut-brain connection is a two-way street, and research shows that feeling stressed can lead to uncomfortable symptoms including stomach pain, diarrhoea, bloating and constipation - some of which are experienced more intensely in those with Irritable Bowel Syndrome (IBS).(5).
A lot of what we initially learnt about the gut-brain axis came from studies in mice. Researchers found that transferring gut microbes from stressed mice into calm mice caused the calm animals to develop anxiety-like behaviours (6). When microbes from healthy mice were transferred into stressed animals, stress responses improved (7). These experiments helped demonstrate just how powerful gut microbes can be in shaping behaviour, stress, mood, and emotional resilience.
How does what we eat impact stress?
Over the past two decades, human studies have shown that dietary changes can meaningfully influence how we respond to stress (8). In one study, participants who followed a “psychobiotic” diet - rich in prebiotic fibres, legumes, fruits, vegetables, and fermented foods - reported lower perceived stress compared with those who maintained their usual eating habits (9).
Unlike our genetics, the gut microbiome is highly adaptable. Diet, lifestyle habits, sleep, and stress levels can rapidly reshape the gut’s microbial communities, sometimes in as little as 24-48 hours (10). This flexibility presents an important opportunity: by supporting our gut microbiome, we can also improve our resilience to stress and stress-related conditions.
So if the gut and brain are constantly communicating, food becomes an important part of that conversation.
Fibre
One of the most important dietary components here is fibre. Unlike protein, fat, or carbohydrates, fibre is not digested by us. Instead, fibre passes into our large intestine, where it serves as food for our beneficial gut microbes.
When these microbes break down fibre, they produce compounds called short-chain fatty acids (SCFAs). These compounds help maintain the gut lining, regulate inflammation, and send signals to the brain through both the bloodstream and the vagus nerve. In one study, delivering SCFAs directly into the large intestine led to lower cortisol levels (your stress hormone) and reduced perceived stress (11).
But when it comes to fibre, consistency and diversity matter more than any single “superfood.” Diets rich in a wide variety of plant-based fibres tend to promote a more diverse microbiome, and this microbial diversity is linked to greater stability and adaptability during periods of stress.
Probiotics
Alongside our diet, new research is showing that probiotics may also play a role in supporting the gut-brain axis. Probiotics are live microorganisms that provide health benefits when consumed in adequate amounts, but the benefits are strain-specific – there’s not a one-size-fits-all. Some of these strains are sometimes called psychobiotics because of their potential effects on mood and emotional wellbeing, (12). Early research suggests they may interact with the gut–brain axis by influencing neurotransmitters involved in mood regulation, as well as the body’s stress response system, known as the hypothalamic–pituitary–adrenal (HPA) axis (13).
However, while these emerging human studies are promising, there’s still more research needed before we can confidently determine their effects (14).
Healthy fats
Healthy fats also play an important role in the gut–brain connection. Omega-3 fatty acids found in foods like walnuts, flaxseeds, and oily fish support brain cell structure and communication. They also help regulate inflammation, protect important barriers in the body such as the gut lining and blood–brain barrier, support processes involved in learning and mood regulation, and balance the body’s stress response by moderating cortisol production (15).
Our 6 gut health tips to improve your stress response
While research in this field is still emerging, we already know enough to take meaningful steps toward supporting a healthier stress response today. Here are our top 6 tips:
1. Plant-based diversity
Aim for 30 different plant points each week across what Dr Megan Rossi calls the Super Six (vegetables, fruits, legumes, wholegrains, nuts and seeds, plus herbs and spices). These offer different types of fibre, nutrients, and polyphenols, which your microbes love. Variety is more important than volume – different microbes prefer different plant foods. That’s why a handful of different plants is better than a mountain of spinach alone.
2. Fermented foods
Fermented foods provide live microbes that can support gut microbiome diversity. You don’t need large servings to get the benefits. A spoonful of yogurt, kefir, or fermented vegetables (like kimchi or sauerkraut) is a great place to start. Build up your intake slowly and find what you enjoy.
3. Healthy fats
Aim to include omega-3-rich foods like oily fish (e.g., salmon, sardines), walnuts, chia seeds, or flaxseeds 3 times per week - twice a week for oily fish - to support brain and cognitive health.
4. Forest bathing
Spending time in green spaces like forests has been shown to lower cortisol (16) and improve blood pressure (17) - both improvements linked to a healthy stress response. Importantly, these studies found benefits in the short-term (one walk in a forest), but for long-term benefits, you could aim for a walk in a green space once a week.
5. Daily movement
Early research shows that aerobic activity has been linked to increased microbial diversity and higher production of SCFAs (18). Bonus points if you exercise in a forest or green space.
6. Scheduling relaxation
To manage stress long-term, build relaxation activities into daily life that you can stick to, like mindfulness, deep breathing, yoga or a even warm bath. It can start with just 5 minutes.
References
1. Mental Health Foundation: Stressed nation: 74% of UK 'overwhelmed or unable to cope' at some point in the past year. https://www.mentalhealth.org.uk/about-us/news/survey-stressed-nation-UK-overwhelmed-unable-to-cope
2. Cryan JF, O'Riordan KJ, Cowan CSM, Sandhu KV, Bastiaanssen TFS, Boehme M, Codagnone MG, Cussotto S, Fulling C, Golubeva AV, Guzzetta KE, Jaggar M, Long-Smith CM, Lyte JM, Martin JA, Molinero-Perez A, Moloney G, Morelli E, Morillas E, O'Connor R, Cruz-Pereira JS, Peterson VL, Rea K, Ritz NL, Sherwin E, Spichak S, Teichman EM, van de Wouw M, Ventura-Silva AP, Wallace-Fitzsimons SE, Hyland N, Clarke G, Dinan TG. The Microbiota-Gut-Brain Axis. Physiol Rev. 2019 Oct 1;99(4):1877-2013. doi: 10.1152/physrev.00018.2018. PMID: 31460832.
3. Sherwin E, Bordenstein SR, Quinn JL, Dinan TG, Cryan JF. Microbiota and the social brain. Science. 2019 Nov 1;366(6465):eaar2016. doi: 10.1126/science.aar2016. PMID: 31672864.
4. Li Y, Hao Y, Fan F, Zhang B. The Role of Microbiome in Insomnia, Circadian Disturbance and Depression. Front Psychiatry. 2018 Dec 5;9:669. doi: 10.3389/fpsyt.2018.00669. PMID: 30568608; PMCID: PMC6290721.
6. Li N, Wang Q, Wang Y, Sun A, Lin Y, Jin Y, Li X. Fecal microbiota transplantation from chronic unpredictable mild stress mice donors affects anxiety-like and depression-like behavior in recipient mice via the gut microbiota-inflammation-brain axis. Stress. 2019 Sep;22(5):592-602. doi: 10.1080/10253890.2019.1617267. Epub 2019 May 24. PMID: 31124390.
7. Langgartner, D., Vaihinger, C. A., Haffner-Luntzer, M., Kunze, J. F., Weiss, A. L. J., Foertsch, S., ... & Reber, S. O. (2018). The role of the intestinal microbiome in chronic psychosocial stress-induced pathologies in male mice. Frontiers in behavioral neuroscience, 12, 252.
8. Foster, J. A., Rinaman, L., & Cryan, J. F. (2017). Stress & the gut-brain axis: regulation by the microbiome. Neurobiology of stress, 7, 124-136.
9. Berding, K., Bastiaanssen, T.F.S., Moloney, G.M. et al. Feed your microbes to deal with stress: a psychobiotic diet impacts microbial stability and perceived stress in a healthy adult population. Mol Psychiatry 28, 601–610 (2023). https://doi.org/10.1038/s41380-022-01817-y
10. David LA, Maurice CF, Carmody RN, Gootenberg DB, Button JE, Wolfe BE, Ling AV, Devlin AS, Varma Y, Fischbach MA, Biddinger SB, Dutton RJ, Turnbaugh PJ. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014 Jan 23;505(7484):559-63. doi: 10.1038/nature12820. Epub 2013 Dec 11. PMID: 24336217; PMCID: PMC3957428.
11. Dalile B, Vervliet B, Bergonzelli G, Verbeke K, Van Oudenhove L. Colon-delivered short-chain fatty acids attenuate the cortisol response to psychosocial stress in healthy men: a randomized, placebo-controlled trial. Neuropsychopharmacology. 2020 Dec;45(13):2257-2266. doi: 10.1038/s41386-020-0732-x. Epub 2020 Jun 10. PMID: 32521538; PMCID: PMC7784980.
12. Sarkar, A., Lehto, S. M., Harty, S., Dinan, T. G., Cryan, J. F., & Burnet, P. W. J. (2016). Psychobiotics and the manipulation of bacteria-gut-brain signals. Trends in Neurosciences, 39(11), 763–781. https://doi. org/10.1016/j.tins.2016.09.002
13. Mörkl, S., Butler, M.I., Holl, A. et al. Probiotics and the Microbiota-Gut-Brain Axis: Focus on Psychiatry. Curr Nutr Rep 9, 171–182 (2020). https://doi.org/10.1007/s13668-020-00313-5
14. Zhang N, Zhang Y, Li M, Wang W, Liu Z, Xi C, Huang X, Liu J, Huang J, Tian D, Mu J, Liao X, Zhai S. Efficacy of probiotics on stress in healthy volunteers: A systematic review and meta-analysis based on randomized controlled trials. Brain Behav. 2020 Sep;10(9):e01699. doi: 10.1002/brb3.1699. Epub 2020 Jul 14. PMID: 32662591; PMCID: PMC7507034.
15. Zinkow, A., Grodzicki, W., Czerwińska, M., & Dziendzikowska, K. (2024). Molecular mechanisms linking omega-3 fatty acids and the gut–brain axis. Molecules, 30(1), 71.
16. Antonelli, M., Barbieri, G. & Donelli, D. Effects of forest bathing (shinrin-yoku) on levels of cortisol as a stress biomarker: a systematic review and meta-analysis. Int J Biometeorol 63, 1117–1134 (2019). https://doi.org/10.1007/s00484-019-01717-x
17. Ideno, Y., Hayashi, K., Abe, Y. et al. Blood pressure-lowering effect of Shinrin-yoku (Forest bathing): a systematic review and meta-analysis. BMC Complement Altern Med 17, 409 (2017). https://doi.org/10.1186/s12906-017-1912-z
18. Varghese S, Rao S, Khattak A, Zamir F, Chaari A. Physical Exercise and the Gut Microbiome: A Bidirectional Relationship Influencing Health and Performance. Nutrients. 2024 Oct 28;16(21):3663. doi: 10.3390/nu16213663. PMID: 39519496; PMCID: PMC11547208.
Written by Corrine Toyn - Registered Dietitian
Reviewed by Rachel Redman, Registered Dietitian
