How Gut Bacteria is linked to Mental Health
Your colon is home to trillions of bacterial cells which make up a unique ecosystem called the gut microbiome. As well as allowing nutrients to enter the body and keeping opportunistic pathogens locked out, their activities also influence your brain.
When the body is exposed to stress, it goes through a series of changes so that all energy and major resources are directed to the muscles and brain. Stress also causes the body to release cortisol, and all these factors can affect the gut microbiome.
Equally, if your gut microbiome is imbalanced (dysbiosis), then your overall mood can be affected. That’s because the activity of your gut bacteria affects stress and anxiety — a balanced microbiome can improve your stress resilience, but an imbalanced one can affect your mental health. Here’s how probiotics depression, gut bacteria and mental health are linked.
1. The vagus nerve connects your gut and your brain
Your gut and brain are connected by the vagus nerve, a major component of the autonomic nervous system which enables you to breathe, digest food, and swallow automatically. This nerve is able to send messages to your brain for your colon, and vice versa.
The connection between the two organs means that the gut-brain axis is becoming a vital player in mental health, illnesses that affect the brain, and even irritable bowel syndrome (IBS). It explains why stress can take a toll on your digestion, but also why digestive problems can make you unhappy.
2. Gut bacteria talk to your brain too
Gut bacteria break down food, particularly dietary fibre, and transform it into metabolites like short-chain fatty acids (SCFAs). These are detected by the nerve which then sends data to the brain, allowing the regulation of digestive processes.
On the other hand, when the vagus nerve is impaired by stress (that directs energy and attention to your muscles and brain), it can’t react effectively to inflammation, which is bad for your gut and your gut bacteria. And that’s why your vagus nerve is so important.
3. Inflammation, gut bacteria, and depression
To support your health, your gut microbiome needs to be diverse, and diversity helps keep it balanced. However, if it is not balanced — something called “dysbiosis” — opportunistic microbes can take advantage and proliferate, resulting in inflammation.
That’s because your body doesn’t want opportunistic bacteria, so your immune system is alerted, resulting in inflammation. Interestingly, inflammation can contribute to depression, and depression can cause inflammation. But a diverse microbiome can prevent inflammation.
So, controlling inflammation can help to improve both mood and anxiety levels. Diet is one way to increase the abundance of diverse microbes and reduce inflammation. Beneficial gut bacteria thrive on a natural, plant-based diet because fiber is an important source of energy for them.
4. Gut bacteria and mental health: the butyrate effect
Butyrate is an essential short-chain fatty acid produced by good gut bacteria when you eat plants (fruit, veg, seeds, nuts, whole grains, legumes). It doesn’t just keep your gut happy, your brain benefits too. A microbiome test by AtlasBiomed can show you how much butyrate is produced by your gut bacteria.
Butyrate is the main source of fuel for the cells of your gut lining, so it helps keep this barrier strong and intact. It also helps prevent inflammation, which can be bad for your mood. A new study even shows that butyrate might help you grow new brain cells. However, if you have dysbiosis, your gut bacteria might make less important nutrients, including butyrate.
The great news is you can actively contribute to the butyrate production in your gut through your diet. One way is by eating prebiotics — foods which directly provide sustenance to your gut bacteria, like fruit, vegetables, whole grains, and pulses. These contain fibre which is transformed into SCFAs like butyrate. So, increasing your intake will positively affect your health!
5. Probiotics and depression
Probiotic bacteria provide many health benefits, including for the brain. They naturally reside in the gut but are also found in supplements and fermented foods, like yoghurt and kefir. Bifidobacterium, Lactobacillus, and Lactococcus species are all examples of probiotics because they support your whole-body and improve mental health too.
Psychobiotics is a field which investigates the effects of probiotics and mental health. Some research shows that certain Lactobacillus species improve stress resilience and anxiety. Some studies even show that taking probiotics can help alleviate symptoms of depression.
Probiotics help to support human health by keeping the gut ecosystem balanced and preventing dysbiosis. By doing so, beneficial bacteria can thrive and contribute to your health and butyrate production. The positive link between probiotics and depression is already showing great promise.
6. Eat prebiotics to nourish probiotic bacteria
So, you’ve upped your probiotic intake, but to reap all their health benefits, you need to keep them nourished. Just like you, your gut bacteria need food to keep them sustained, energised, and thriving. That’s where prebiotics come in.
Prebiotics are substances found in plant-based foods which maintain beneficial gut bacteria. Prebiotic fibres, polyphenols, and resistant starches all nourish gut bacteria which in turn transform them into good things like SCFAs and vitamins.
Prebiotic food list
Prebiotic fibres - Garlic, Onions, Berries, Artichokes, Barley, Rye, Mushrooms
Resistant starches - Legumes, seeds, grains, Cooked and cooled potatoes, green bananas, Plantain, corn
Polyphenols - Onions, apples, tea, cocoa, red wine, red fruit, soybeans
Research has also shown that consuming prebiotics is also associated with a reduction in anxiety-related behaviour. So it’s important to never underestimate the role of your diet in improving mental wellbeing. You can actually get personalised food recommendations for your gut bacteria if you take a gut microbiome test like this one here.
7. Gut microbes regulate happy hormones
So, you know that your gut microbes are pretty cool and transform food into short-chain fatty acids? Well, these SCFAs communicate with cells which produce serotonin, a neurotransmitter (and a hormone) that regulates your mood, as well as levels of anxiety and happiness. Basically, your gut microbes can help your body produce more serotonin.
Equally, another neurotransmitter, Gamma-Aminobutyric Acid (GABA), regulates and improves mood because it helps to calm the nervous system and switch off stress reactions. Amazingly, some probiotic gut bacteria can even produce GABA themselves for your body.
Fundamentally, your diet can help your bacteria protect your mental wellbeing because eating the right foods feeds happy bacteria. And when you have lots of different healthy bacteria, your microbiome is more diverse and produces substances which increase mood-lifting chemicals, like serotonin and GABA.
8. Your microbiome composition and mental health
It’s clear there is a link between gut bacteria and depression. The composition of the gut microbiome can tell you a lot about what is going on inside your body. Remember that everyone’s gut microbiome is unique, but diversity is a proven factor in keeping your body (and your mind) healthy.
Fortunately, it’s now easy to get your personal microbiome health status with at-home testing. You can see how diverse your microbiome is, how well it produces butyrate, and even what foods you should eat to support a healthy and happy microbial ecosystem.
9. Balance is the key to happy gut bacteria
It’s easy to think of each of the body’s systems as separate entities, and although they may be in some respects, they are also well connected and can influence each other’s activities. The gut and the brain are prime examples of how changes in one can affect the other.
An imbalanced gut microbiome, or dysbiosis, is associated with many diseases, including mood disorders like depression. Likewise, depression can cause inflammation which can affect the natural ecosystem in the gut. However, promising research shows that probiotics and prebiotics are having positive effects on depression, anxiety, and stress resilience.