When we think about looking after our mental health, we often focus on strategies like staying connected with others, exercising regularly, practising mindfulness, or building in time for self-care. These are all important — but there’s another area that is increasingly being explored: the relationship between your gut and your brain.
Emerging research suggests that the gut microbiome — the trillions of microorganisms living in your digestive system — may play a role in communication between the gut and brain and may be associated with aspects of mood, stress and mental wellbeing.
Importantly, gut health is only one piece of a much bigger picture when it comes to mental health. Nutrition can support overall wellbeing, but it is not a replacement for appropriate psychological or medical support.
The Gut–Brain Connection
Your gut and brain are in constant communication through what is known as the gut–brain axis.
This communication occurs through several pathways, including:
- The vagus nerve, which provides a major communication pathway between the gut and brain
- The enteric nervous system, the network of nerves that helps control the digestive system
- Immune and inflammatory pathways
- Metabolic products produced by gut microorganisms, including short-chain fatty acids
This means that what happens in the gut can communicate with the brain — and the brain can also influence what happens in the gut.
For example, stress can affect digestion and bowel habits, while changes within the gut may also influence signalling pathways involved in mood and stress.
What About Serotonin and Dopamine?
You may have heard that around 90% of serotonin is produced in the gut, or that large amounts of dopamine are produced there.
There is an important distinction to understand.
Most of the body’s serotonin is produced by specialised cells in the gastrointestinal tract. However, gut-produced serotonin does not simply travel to the brain and act as a “feel-good” neurotransmitter. Serotonin produced in the gut has important roles in digestion, gut movement and other bodily functions, while serotonin signalling in the brain is regulated separately.
Similarly, dopamine can be produced in the gastrointestinal tract, but this does not mean that gut dopamine directly increases dopamine levels in the brain.
Gut microorganisms can nevertheless interact with pathways involved in neurotransmitter production and signalling, which is one reason researchers are interested in the gut–brain connection.
So rather than saying that “good gut bacteria produce more serotonin and dopamine and therefore improve your mood”, it is more accurate to say that the gut microbiome may influence several pathways involved in brain and mental health.
Feeding Your Gut: Why Fibre Matters
One of the most practical ways to support your gut microbiome is to regularly eat a variety of plant foods.
Certain types of dietary fibre can be used by gut microorganisms as a source of fuel. Some of these fibres meet the definition of prebiotics, meaning they are selectively utilised by microorganisms and provide a health benefit.
Prebiotic fibres can be found in a range of plant foods, including:
- Wholegrains
- Fruits
- Vegetables
- Legumes and beans
- Nuts and seeds
Not all dietary fibre is technically a prebiotic, but increasing the variety of fibre-rich plant foods in your diet is still a great way to support overall digestive and gut health.
What about 30 different plants a week?
You may have seen the recommendation to eat 30 different plant foods each week.
This idea comes from research suggesting that greater diversity of plant foods is associated with greater diversity of the gut microbiome. However, 30 is not a magic number or a formal dietary requirement.
Rather than becoming stressed about reaching a particular number, think about gradually increasing the variety of plant foods you eat across the week. Herbs, spices, wholegrains, nuts, seeds, legumes, fruits and vegetables can all contribute to this variety.
Even small amounts count.
Fermented Foods, Live Microorganisms and Probiotics
Fermented foods are another area of interest when it comes to gut health.
Some fermented foods contain live microorganisms, including bacteria and yeasts. Examples can include:
- Yoghurt containing live cultures
- Kefir
- Some traditionally fermented vegetables, such as kimchi and sauerkraut
- Some fermented soy products
However, there is an important distinction between a fermented food that contains live microorganisms and a probiotic.
The term probiotic has a specific scientific definition. Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.
This means that simply containing live bacteria does not automatically make a food a probiotic.
For example, kimchi can contain live microorganisms, but the particular microorganisms and amounts can vary between products. Unless a specific microorganism has been identified and there is evidence that it provides a health benefit when consumed in an adequate amount, it is more accurate to describe the food as a fermented food containing live microorganisms rather than automatically calling it a probiotic food.
If choosing fermented foods for their live microorganisms, look for products that have not been heat-treated after fermentation and that indicate they contain live cultures.
What Does the Research Say About Diet and Mental Health?
Research into the gut–brain connection is still developing, but there is growing interest in whether dietary changes can influence mental wellbeing through the gut microbiome and other pathways.
One Australian randomised controlled trial, known as the Gut Feelings trial, investigated whether a high-prebiotic diet, probiotic supplementation, or a combination of the two could influence mental health outcomes in adults experiencing moderate psychological stress.
The eight-week study included 119 adults who were allocated to one of four groups:
- Usual diet
- Probiotic supplement
- High-prebiotic dietary intervention
- High-prebiotic dietary intervention plus probiotic supplement
The researchers assessed a range of outcomes, including mood, anxiety, stress, sleep and wellbeing.
The study found that the high-prebiotic dietary intervention was associated with improvements in some mental health outcomes, including total mood disturbance, compared with the other interventions.
However, it is important not to interpret this as proof that eating more prebiotic foods will prevent or treat mental health conditions.
The study was relatively small and short-term, and research in this area is still evolving. More research is needed to understand exactly how dietary patterns, fibre, gut microorganisms and mental health interact.
What we can take from the research is that a fibre-rich, varied diet is a worthwhile part of an overall healthy lifestyle, while the potential gut–brain benefits remain an active area of research.
Practical Ways to Support Your Gut and Overall Wellbeing
You don’t need to completely change your diet overnight.
Small, realistic changes can help you increase the variety of plant foods and fibre in your diet:
- Add fruit, nuts or seeds to breakfast
- Choose wholegrain bread, cereals, pasta or rice more often
- Include vegetables at lunch and dinner
- Add lentils, chickpeas or beans to meals
- Include a variety of fruits and vegetables throughout the week
- Choose yoghurt containing live cultures if you enjoy it
- Try fermented foods such as kimchi or sauerkraut if you enjoy them
- Experiment with different herbs, spices, nuts and seeds to increase plant variety
- Gradually increase fibre intake rather than making a sudden large increase
If you currently eat very little fibre, increasing it gradually and drinking enough fluid can help your digestive system adjust.
And remember — you don’t need a “perfect” gut microbiome or a specific number of plant foods each week. A varied, balanced and sustainable diet is a much more realistic goal.
Take Home Message
Your gut and brain are closely connected, and researchers are continuing to uncover the many ways they communicate.
Eating a varied diet rich in fibre-containing plant foods is one practical way to support your gut health. Fermented foods containing live microorganisms can also be included as part of a varied diet, although it is important to distinguish these foods from products that meet the scientific definition of a probiotic.
There is promising research investigating the relationship between gut health, diet and mental wellbeing, but gut health should be viewed as one part of the bigger picture rather than a standalone solution for mental health.
You don’t need to overhaul your diet. Start with small changes, focus on variety, and choose foods that are realistic and enjoyable for you.
Need Support?
If you’d like help improving your gut health and building a realistic, personalised approach to nutrition, Feed Your Future Dietetics can support you.
With over 10 years of experience, I help individuals develop simple, sustainable nutrition strategies that support their overall health and wellbeing.
Get in touch today:
ashleigh@feedyourfuturedietetics.com
Feed Your Future Dietetics
Australia-wide Telehealth consultations
References
Hill C, Guarner F, Reid G, et al. The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nature Reviews Gastroenterology & Hepatology. 2014;11:506–514.
Freijy T, Cribb L, Oliver G, et al. Effects of a high-prebiotic diet versus probiotic supplements versus synbiotics on adult mental health: the “Gut Feelings” randomised controlled trial. Frontiers in Neuroscience. 2023;16:1097278.
Cryan JF, O’Riordan KJ, Cowan CSM, et al. The microbiota-gut-brain axis. Physiological Reviews. 2019;99(4):1877–2013.
Strandwitz P. Neurotransmitter modulation by the gut microbiota. Brain Research. 2018;1693:128–133.
