Gut health and mental health: what's the link?

Gut health and mental health: what's the link?

Team ErbologyErbology

Gut health and mental health are closely linked. It's a field of research that is only now beginning to flourish, but what do we know so far? 

April 27, 2022 4:55 pm

Going with your gut

Ever faced a tough decision or struggled to figure out how you feel about something? Chances are you might have been advised to ‘go with your gut’!

As it turns out, our gut may be even wiser – and more involved with the workings of our mind – than we thought.

The link between gut health and mental health forms the basis of an emerging field of research which is sparking a lot of interest in the scientific world. A lot of the research available is fairly new, but the number of studies seems to be increasing with each passing year.

Could it be that what we eat directly affects our state of mind? And what role does the gut have to play in all of this?

What do we mean by the ‘gut’?

For lots of us, the term ‘gut’ is quite fuzzy, referring generally to your lower digestive tract where nutrients from food are absorbed.

However, when talking about the link between gut health and mental health, we need to consider another major stakeholder: your gut bacteria.

Your gut is home to about 100 trillion bacteria.(1) Their collective weight adds about four pounds of biomass to each person – which is more than the weight of our brains!

Some of these bacteria are really beneficial to our health, while others are less helpful. Generally speaking, the ‘good’ bacteria help to keep the ‘bad bacteria in check by maintaining their populations at a healthy level. They live in a delicate balance which is, at least in part, dependent on the food you eat. All together, this fascinating ecosystem of bacteria is known as your gut microbiome.

What’s more, your gut microbiome is as unique to you as your fingerprint. Even if you eat the same diet, your gut microbiome will be slightly different from that of other members of your family or your friends.

It performs so complex a role in our bodies that some scientists have even begun to refer to it as the ‘third brain’.


Oriental no-meat balls

Gut health and mental health

So, we know that the bacteria in our gut have a bigger role to play in our health and wellbeing than we realised. But how do they affect your mental health?

If you have ever suffered from difficulties with your mental health, you will know that stress is a major trigger for many disorders. Capable of setting off panic attacks, increasing anxiety and leading to depression, stress is a factor that many people have to manage daily to maintain their mental health.

Scientists have discovered that the gut microbiome plays a very important role in allowing us to manage stress normally.

Researchers looked at what happened when there are no microbes living in the gut. This helped them to understand exactly how the gut microbiome influences our lives.(1) They discovered that, without gut microbes, a process called ‘myelination’ does not happen as usual.

Myelin is a substance made up of protein and fatty substances which forms a layer around nerve fibres. It acts as insulation, preventing electrical signals from escaping and helping them to reach the right place. Without myelination, nerve signals stay isolated. Myelin also helps our brains to stay fluid and adaptable.(2)

Gut microbes seem to be instrumental in helping to form the genes that tell us how to create myelin.

A lack of myelin affects our response to anxiety and fear. It also slows down our learning and cognition. Stress becomes insurmountable. Together, all of these things are a major burden on what we think of as mental health, and the brain becomes less able to handle everyday obstacles. As a result, our mental and emotional resilience declines.

In short, we need myelin for our mental health, and we need our gut bacteria to make myelin.



Can you alter your gut microbiome?

As mentioned above, your gut microbiome is completely unique to you. However, unlike your fingerprint or your DNA, it’s perfectly possible to alter your gut bacteria.

We know that a healthy diet is instrumental in creating and maintaining a gut microbiome. Lots of diversity in your diet, and plenty of fibre, help too. Avoiding taking unnecessary courses of antibiotics is sensible as well, as these medicines tend to wipe out a lot of the beneficial bacteria in your gut as well as eliminating the bad ones. It may take you some time to build your normal gut microbiome back up after a course of antibiotics.

If you’re interested in changing your gut microbiome with a view to improving your mental health, there are certain types of food which may be especially helpful.

Related reading

Prebiotics, probiotics and psychobiotics

These three terms refer to groups of foods which may help your gut microbiome to stay healthy.

Prebiotics are not digestible by humans, but they can be fermented and broken down by your gut bacteria, which are then able to extract their valuable nutrients. Prebiotics include vegetables. like Jerusalem artichoke, tigernuts, asparagus, onions and garlic. Think of prebiotics as a little care package which reaches your gut bacteria intact and provides them with a nourishing meal.

Probiotics are foods which contain live bacteria. The idea is that these beneficial bacteria reach your gut and either increase the population of ‘good’ bacteria, or add another type of useful bacteria into the mix. Examples of probiotics include live yoghurt, sauerkraut, pickles and tempeh.

Want more ideas on which prebiotic and probiotic foods to add to your diet? Head over to our article on prebiotic and probiotic foods.

Meanwhile, ‘psychobiotics’ refers to live bacteria which, when eaten, are thought to have a positive impact on your mental health. However, it’s important to note that research on psychobiotics is in its very early days. Psychobiotics don’t (yet) constitute their own group of foods, but rather it’s thought that some bacteria found in prebiotics and probiotics may act as psychobiotics. → View Related Products

Related reading


risotto with almonds

Gut health disorders and mental health disorders

Researchers have also observed links between gut disorders and mental health problems.

For example, more than a third of people suffering from Irritable Bowel Syndrome (IBS) also struggle with depression.(3) Another study looked at patients suffering from gastrointestinal disorders who were later referred to psychiatrists. More of these patients were diagnosed with psychotic disorders than patients who were referred directly to psychiatrists.(4)

Moreover, 36.5% of patients who have functional gastrointestinal disorders such as functional dyspepsia also have psychiatric disorders. These are often connected to panic or anxiety.(5)

Finally, 60% of patients suffering from acute, consistent constipation also exhibited mental or spectrum disorders.

In some cases, it could be that the symptoms of a gut disorder such as IBS may cause a depression or anxiety response as they can be distressing and disruptive to normal life. However, it’s also possible that there may be a more causal link between gut health disorders and mental health issues.

Hippocrates is credited with the quote, "All diseases begin in the gut."

What do we know about psychobiotics?

As we’ve already talked about, the field of research around psychobiotics is fairly new. Luckily, lots of teams are looking into them and their potential effects for our health.

John Cryan, a scientist doing intensive research into the relationship between the gut and the brain (sometimes called the gut-brain axis) looked into one particular type of bacteria: Bifidobacterium longum 1714. He put it into capsules and gave it to 22 male research participants for a month.

The subjects experienced less stress and anxiety and were also were able to complete memory exercises with more accuracy. Perhaps most significantly, they exhibited lower levels of the stress hormone cortisol at the beginning of the day.(6) This means that, before anything had the chance to rile them up, they were starting the day with an emotionally balanced state of mind.

Although we are not certain yet exactly how these bacteria may effect these changes, it’s possible that they stimulate the vagus nerve. This nerve runs between the gut and the brain and facilitates communication between the two.

If just one type of bacteria can effect so noticeable a change, imagine what the perfect balance of different types could achieve! Pinpointing the way that individual bacteria types function within our bodies, both together and alone, might allow us to understand which are needed for good health, and where imbalances might be occurring.

Theoretically, that might give us the chance to create the right bacterial balance through diet and lifestyle choices, rather than relying on supplements and medical treatments. It’s a really exciting time for researchers in this field, and their work continues to provide fascinating new insights.


asparagus recipe

What about prebiotics and mood?

Other studies have looked specifically at prebiotics and how they impact mood.(7)

Scientists found a similar lowering of waking cortisol levels. They also found that their subjects paid greater attention to positive imagery. In other words, people who took prebiotics were more likely to see the positive than the negative. This is even more exciting when we consider that humans are probably hardwired to look for the negative in any situation, as this helps us to identify threats to our safety.

Although scientists have cautioned against thinking that serious psychiatric disorders could be fully healed with prebiotics, there’s still plenty of reason to be pleased. For example, its possible that people taking medications for certain mental health issues might get better results from their medication, if they’re already predisposed towards positivity.

Prebiotics also have significance for mental health in broader ways. One of the most important ingredients for overall mental and emotional wellbeing is good sleep. It is also one of the most elusive, with many people in Western societies struggling to obtain enough quality sleep. While aids like sleeping pills might be effective in the short-term, they are not a good long-term solution.

Luckily, it turns out that prebiotics may be helpful in getting a good night’s sleep. Both anecdotal evidence and a few promising studies suggest that prebiotics may lessen the effects of stress during your waking hours and during the various stages of sleep. This results in a smoother sleep cycle altogether.(8)

Recipes for your gut health


Jerusalem artichoke granola

Dr Mosley’s good night’s rest

Just one of the anecdotal examples of prebiotics helping with rest was recorded for a BBC programme in 2017. A documentary called “The Truth about Sleep” focused on Dr. Michael Mosely, an insomniac who was looking into ways to improve his ability to sleep.

As part of the documentary, Dr. Mosley looked into various factors including diet and lifestyle and how they impact sleep. He explained that he had struggled with sleeplessness for many years and tried different strategies to attain better sleep, all to no avail.

When he came across prebiotics, however, Dr. Mosley had a breakthrough in his sleep patterns. He could fall asleep more quickly and stay asleep longer. Further, he slept better and more deeply.

Related reading

Stress and trauma

One fascinating study found another strange link between mental health and the activities of your gut microbiome.

The research was based in South Africa, where incidents of trauma and violence are unusually common. Around 75% of the population has experienced at least one traumatic event in their lifetime. The high level of trauma has been linked with a higher prevalence of disease in the population.

In trying to understand how society could better prevent and deal with these issues, researchers looked at the effects of stress in the gut. They compared the microbiota of healthy people with those of a number of people suffering from post-traumatic stress disorder (PTSD). Although the samples were broadly similar, patients with PTSD had a lower number of three types of bacteria in their gut: Actinobacteria, Lentisphaerae, and Verrucomicrobia.(9)

In short, the gut can help us deal with stress, but it can also be affected by it.

Studies looking at the connection between sleep and the gut also revealed the same things – that lack of sleep led to changes in the bacteria makeup of our gut microbiome.


gut health

The new frontier

Given the evidence stacking up which suggests that our gut health is intrinsically linked to other areas of our wellbeing, adopting a lifestyle and diet which caters to the trillions of tiny guests travelling with you may be a positive move.

As suggested above, a healthy gut microbiome may allow you to sleep better, improve your resilience and help treat certain mental health disorders.

The Greek physician and philosopher Hippocrates, widely considered to be the father of modern medicine, may have sensed its importance long ago. “All diseases begin in the gut,” he claimed. Now, it appears his words have been borne out, although possibly not as he might have predicted!

As modern science continues to make fascinating new discoveries about our gut bacteria, we can at least take the step to keep them nourished and cared for. So, why not add prebiotics and probiotics to your diet? As well as improving your digestion, they may just help with your mental wellbeing, too.

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  • References

    (1) ‘Can gut bacteria improve your health?’ Harvard Health Publishing

    (1) Luczynski et al, “Growing up in a Bubble: Using Germ-Free Animals to Assess the Influence of the Gut Microbiota on Brain and Behaviour”, International Journal of Neuropsychopharmacology, 2016.

    (2) Radulescu et al, “Manipulation of microbiota reveals altered callosal myelination and white matter plasticity in a model of Huntington disease.”  Neurobiology Diseases, 2019.

    (3) Shah et al, “Psychological disorders in gastrointestinal disease: Epiphenomenon, cause or consequence?” Annals of Gastreoenterology, 2014.

    (4) “Gastrointestinal Symptoms in Psychiatry: Comparison of Direct Applications and Referrals..

    (5) Stasi et al, “Subthreshold psychiatric psychopathology in functional gastrointestinal disorders: Can it be the bridge between gastroenterology and psychiatry?” Gastreoenterology Research and Practice, 2017.

    (6) Ian Sample, “Probiotic bacteria may aid against anxiety and memory problems”, The Guardian, 2015.

    (7) Schmidt et al, “Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers” Psychopharmacology, 2015.

    (8) Thompson et al, “Dietary Prebiotics and Bioactive Milk Fractions Improve NREM Sleep, Enhance REM Sleep Rebound and Attenuate the Stress-Induced Decrease in Diurnal Temperature and Gut Microbial Alpha Diversity”, Frontiers in Behavioural Neuroscience, 2017.

    (9) Hemmings, Sian M J et al. “The Microbiome in Posttraumatic Stress Disorder and Trauma-Exposed Controls: An Exploratory Study.” Psychosomatic medicine vol. 79,8 (2017): 936-946. doi:10.1097/PSY.0000000000000512

    Photo credits: Gaelle MarcelJana Sabeth.

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