Mood + Food - using our gut bacteria to influence our state of mind
It can be alarming to know that our gut microbiota -- all the microorganisms in our digestive tract -- can influence our mood, levels of anxiety or depression.
Now this is not the same as saying it is the cause of these states, but that recent research is uncovering the intricate relationship between these two distinct areas.
The fact is the microbiome can 'speak' directly to the brain via a variety of mechanisms. A primary way though, is via the vagus nerve.
So what is the vagus nerve and how does it 'speak' to the brain?
The vagus nerve interacts with and spreads messages from the belly to the brain, with checkpoints at the heart and lungs.
Think of it as a nerve transmission highway connecting the activity of the gut with the state of the brain and vise versa.
A diverse and healthy gut microbiome can impact the brain by:
What they produce. When bacteria feast on the remains of our food they produce ‘waste’ products or metabolites that influence our neurotransmitters and can either improve or worsen how we feel. They can also directly stimulate our immune system and play a role in regulating inflammation.
Stimulating the vagus nerve to trigger or dampen stressed or anxious states. Remember we said the vagus nerve has checkpoints at the heart and lungs? Besides creating urgency, in stressed states you may begin to breath a bit shallower and experience an increased heart rate.
Disturbances in our gut bacteria can lead to poor communication, inflammation and reduced chemical messengers. This is when we are at risk of unbalanced mental states.
Key products we want from our microbiome
Serotonin and GABA are key messengers involved in influencing our mood and the quality of our intestinal environment.
Serotonin is an essential mood regulating neurotransmitter often hailed as the ‘happiness hormone’.
Low levels of serotonin are implicated in anxiety disorders, sleep disruption and associated depression (8). It is so essential in the treatment of mood disorders that drugs targeting anxiety often increase serotonin uptake.
The fascinating aspect of serotonin is that despite being involved in mental health, 90% is manufactured via our gut! (9) Here it influences our gut immune system and helps to protect our intestinal nervous system cells.
GABA is also therapeutic for mental health, particularly anxiety, as GABA is a calming neurotransmitter which dampens down anxious neural pathways. GABA and serotonin both stimulate the vagus nerve. The vagus nerve impacts our mood, digestion, heart rate and immune response, showing just how fundamental the state of our gut can be for the state of our mind.
The good news is we have the capacity to influence the amount of chemical messengers the body produces, by influencing the levels of bacteria involved in their production.
Certain species are shown to be great aids in the creation of these neurotransmitters, specifically Lactobacillus, Bifidobacterium, Clostridium and more- see Serotonin stars and GABA Soothers below to learn which foods will encourage these species to flourish in your gut.
Of course, if these species are lacking, and the bacteria within the gut is unable to manufacture the appropriate quantities of these chemical messengers, we may be more at risk of the negative impacts of dysbiosis and associated inflammation, namely poor serotonin production/ impaired GABA levels, and possible increases in anxiety and low mood.
Scientists have known for a long time about a ‘gut-brain’ connection, noting the impact of stress on an individual’s stomach acid secretions1. Yet, only recently has there been further investment in uncovering the intricate relationship between our microbiome and brain.
The aspects of our gut health which most influence our mental state include:
The diversity of the microbiome (4);
The integrity of the gut wall lining (5); and
Any form of dysbiosis (6) -- ie. overgrowth of pathogenic bacterium.
In general, the dysbiotic microbiome, will be more likely to create levels of inflammation in the gut, which correspond to unhealthier mental states (7).
We can manipulate the state of our microbiome through a number of achievable and sustainable changes.
Food for gut repair and to treat our mood
The gut becomes more susceptible to dysbiosis, inflammation and something known as visceral hypersensitivity with stress and anxiety.
Visceral hypersensitivity is essentially a heightened awareness of sensations in the gut such as increased air from fermenting food, which may trigger the pain symptoms and motility issues (yes, urgency) associated with IBS.
If you suffer from IBS, it is important to acknowledge that stress can contribute to the dysbiosis in turn causing or worsening the symptoms. Stress management is an essential approach to address symptoms.
Similarly, an imbalanced microbiome may be directly responsible for some of the symptoms sufferers experience (10), and rectifying such issues can lead to an elimination of symptoms in many cases. Especially when patients also have a small intestinal bacterial overgrowth (SIBO)(11).
Research shows that we need to take both:
a bottom up approach → manipulating the diet to ensure a harmonious gut ecosystem; and
a top down approach → reducing stress levels to calm an inflamed, unbalanced gut.
Bottom up choices to improve our mental health
Diet and lifestyle are the key factors we can change to influence our microbiome (the others factors -- that we are less able or unable to change are geography and genetics)
This in turn influences our capacity to make sufficient levels of both serotonin and GABA, our feel-good duo.
A healthy gut is a diverse one
Each beneficial strain hosts different benefits to the brain and body. Sadly evidence indicates that a standard westernised diet involving processed foods, refined carbs and only a small intake of fibre rich fruit and veg leads to a very limited selection of helpful species choosing to grow in our gut (13). Conversely, when studies examined the microbiome of tribes in rural Africa who ate whole food plant-based style diets the diversity and therefore health of the gut was significantly increased (14). Eating a variety of different plant-based foods is an easy way to enhance diversity as well as making life more interesting!
Integrity prevents inflammation
If we have a lack of tight junctions in the defensive gut wall barrier, sometimes described as a leaky gut or hyper-permeability, then we are at risk of invading pathogens (5), and other threats entering or leaving when they shouldn’t. This in turn can trigger an inflammatory cascade, influencing the balance of the gut bacteria and may hamper gut- brain relations.
We can keep our defenses strong with the adequate production of short chain fatty acids such as butyrate (15) by encouraging species like roseburia (16)- by eating a wide range of prebiotic fibres such as garlic, green bananas and oats.
Serotonin stars: the following species are particularly important when it comes to upping our feel-good factor:
Clostridium species can make their own serotonin supplies (17), and therefore should be welcomed with open arms. We can encourage them to set up camp by favouring a mediterranean style diet (18), avoiding processed fats and enjoying lots of delicious papaya (19).
Bifidobacteria- you have probably heard of this strain as it is found in many commercial ‘live’ dairy products such as yoghurts and kefir. It has unique abilities to reduce patient anxiety during trials (20). Boost your bifido by including kimchi and loading up on fibre.
Lactobacillus- by increasing this beneficial strain we can support tryptophan production which is a direct precursor to serotonin (21). Whilst tryptophan is found in foods such as peanuts, bananas, and dried prunes we can also load up on lactobacillus via olives, pickles and sourdough.
GABA Soothers: when it comes to supporting GABA we need to both increase beneficial species whilst discouraging those which may impair its production
Species of benefit include Lactobacillus brevis, Alistipes putredinis and Dorea longicatena (22), which can be increased via regular consumption of cruciferous vegetables (23) chicory/radicchio/endive, asparagus, whilst avoiding gluten free diets unless essential (24).
Species to discourage include Flavonifractor sp. which can be discouraged by avoidance of an excessively high fat diet (25), focusing instead on plant-based fibres.
Top down factors to improve our mental health.
It is no good eating a diverse diet, rich in beneficial pre- and probiotics, if we are in a state of chronic stress. We have learned that stress negatively impacts the health of our microbiome and therefore our ability to ‘mood regulate’ is hampered.
There are many methods of encouraging a helpful brain-gut interaction.
When we calm the mind- we tell the gut it too can relax -- and therefore digest our food, focus on serotonin and GABA production, whilst carrying out any essential repair work on the gut wall.
Evidence tells us exercise can modulate our anxiety and mood in more ways than one. Did you know that exercise can increase Bifidobacterium (26)?
Mindfulness and meditation practices lower the gut modulating stress hormone, cortisol (27).
The simple act of spending time outdoors can benefit our mind and body alike (28).
A good piece of news if you are a pet owner -- time spent around dogs and cats not only enhances the microbiome through exposure to different bacteria (29), it also reduces stress such that your gut benefits!
KEY TAKE-AWAYS
As with most areas of health, a holistic approach is required to best support our mind body interactions. We know that the gut speaks to the mind and vise versa and therefore by optimising the state of one, we can support the health of the other. This has wide ranging implications for our mood and wellbeing, and also plays a role in the management of chronic mind body disease states such as IBS.
EAT a diverse diet
INCLUDE pre and probiotics
UP plant based foods
AVOID high fat, processed low fibre diets
RUN, hop or skip your way to better health, preferably outside
RELAX, knowing by reducing stress you are supporting your gut, to support you.
References
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