Mental Health And The Gut-Brain Connection – It’s More Complicated Than You Think
If you work to look after your mental health, you may have heard about the gut-brain connection. You may be curious as to why the gut is often considered the ‘second brain’. You may be wondering: Is there a link between gut health and mental health? What is the connection between gut, brain and depression?
For a long time, the gut might be the last place a person looked when concerned about their mental health. What’ve intestines got to do with it? But nowadays from Instagram ads to influencer chatter, the gut-brain connection is increasingly a buzzword and it can be difficult to separate fact from factoid. So what actually is the gut-brain connection? How much do we really know about it and what does it mean for your mental health? Read on to learn more about mental health and the gut-brain connection.
First things first – what do we mean by ‘the gut’?
The gut is an informal term for your gastrointestinal (GI) system – the passage which the foods and liquids you ingest travel down, all the way from the mouth to the anus.
But when people talk about ‘the gut’, they’re most often referring to the stomach and intestines, as in phrases like:
- Go with your gut
- What is your gut telling you?
- I have a gut feeling
- That’s just my gut instinct
- Listen to your gut
These expressions convey the idea that the sensations you feel in your tummy have important information for you. We’ve been saying them forever without thinking about it, but science is increasingly discovering that there is a significant gut-brain connection.
Gut health is in large part governed by the balance of different kinds of bacteria within it. And it turns out that gut health plays a crucial role in brain health. Read on to learn more.
What is the gut-brain connection (and why the gut is often considered the ‘second brain’)
What is the gut-brain connection? The answer to this is complicated and still emerging. Science is only just beginning to understand it. But here are some things we do know:
- The brain and the gut communicate with each other about physical and emotional issues. From food poisoning signals to the nervous butterflies you feel when you’re about to do something scary, your brain and gut are in constant two-way communication.
- Your brain talks to every part of your body through neurons (nerve cells), in a complex network we call the nervous system. The nervous system has a number of divisions and sub-divisions, one of which is the enteric nervous system (ENS). The ENS is an intricate network of nerve cells in the gut which governs things like digestion, blood flow, and inflammatory and immune responses. 100 million nerve cells make up the gut’s enteric nervous system – more than any part of your body other than your brain!
- To some extent the ENS can function independently of the brain, which is why the gut is often considered the ‘second brain’.
- In addition, the ENS employs many of the same chemicals and cells as the brain, to aid digestion and warn the brain when something is wrong.
- More communication takes place between your gut and your brain than any other system in your body. From hunger signals and reactions to food, to nervousness and excitement, your gut and your brain are in constant contact.
- Your gut bacteria are key to the synthesis of important chemical messengers involved in regulating mood and behaviour (such as serotonin and dopamine). Nutrients in the foods we eat are precursors to the brain’s chemical messengers – for example foods like chicken and nuts contain tryptophan, which your body needs to make serotonin.A healthy gut microbiome can make those nutrients more bioavailable and more effectively synthesised.
Is there a link between mental health and gut health?
Yes! For a long time when people referred to the ‘mind-body connection’, they were asserting that stressors could affect a person’s physical health. However, it’s increasingly understood that the relationship goes both ways.
While it has long been acknowledged that chronic stress could impact the gut microbiome, there is increasing evidence that the gut microbiome affects the central nervous system. The microbiota in your gut can affect your mood, perceptions and emotions. The gut-brain connection is a two-way relationship.
But wait – what do we mean by the gut microbiome and what role does it have in the gut-brain connection?
The gut microbiome refers to the community of life forms that live in the intestines – such as ‘good’ and ‘bad’ bacteria, fungi, parasites and viruses. There are as many as 1000 different bacteria species in the gut microbiome, with different bacteria playing different roles. The gut microbiome is crucial in digesting the food we eat, absorbing nutrients, and managing the immune system. Diversity of gut bacteria is important for good health.
Here’s a fascinating fact that is often touted in a misleading way: 90% of serotonin is produced in the gut.
Serotonin is famously the brain’s ‘feel good’ messenger. But many people don’t know that serotonin is about much more than mood! So while the 90% figure is true (approximately), gut-derived serotonin generally doesn’t actually breach the blood-brain barrier. Instead, it works to regulate your gastrointestinal activity. Gut-derived serotonin helps with things like nutrient absorption, transportation and other digestive functions.
While the gut isn’t directly producing your brain’s serotonin, there are many ways that gut microbiota and gut activity can affect mental health, including:
- Gut-derived serotonin helps with nutrient absorption – and the nutrients in the foods we eat are the precursors to the brain’s chemical messengers (including serotonin).
- The gut microbiome plays an early role in the production of the brain’s vital neurotransmitters that govern mood and behaviour (like dopamine, GABA, and serotonin). As explained, some nutrients in the foods we eat are precursors to the brain’s chemical messengers. A healthy gut microbiome will more effectively break down these nutrient precursors that will later be synthesised by the brain to make neurotransmitters.
- Gut microbiota affects the vagus nerve. The vagus nerve helps regulate the brain’s levels of chemical messengers that affect mood – like serotonin, GABA, and glutamate.
- Gut-derived serotonin helps to stimulate the HPA-axis (the hormone system that is key to our body and mind’s response to stress).
- Gut flora imbalance can prompt the body to generate pro-inflammatory proteins (cytokines) which can then be carried to the brain where they can disturb the blood-brain barrier.
- An unhealthy gut microbiota may increase the brain’s permeability, allowing toxins and pathogens to enter the brain, affecting cognition, mood, and memory.
While there is still much to learn, it is increasingly acknowledged that healthy and diverse gut bacteria is crucial to sound thinking and emotional processing.
What is the connection between gut, brain and depression?
Increasingly, science is discovering a relationship between gut microbiota and depression. While the mechanisms driving it still require much study, here are some things we do know:
- A number of research studies have found that people suffering from clinical depression have differences in gut microbiota compared to healthy subjects.
- Experiments with animals have found that transplantation of faecal microbiota (bacteria in poo) from patients with clinical depression into the intestines of rodents can create depression-like behaviours.
- One such study went further, discovering that the transplanted faecal microbiota significantly altered the rats’ levels of neurotransmitters (the brain’s chemical messengers) associated with mood, in addition to creating abnormalities in HPA axis (the hormone system that is key to our body and mind’s response to stress) not to mention a number of other issues including inflammation.
- Gut dysbiosis can lead to the release of pro-inflammatory proteins (cytokines). Not only is depression extremely common among people with chronic inflammatory conditions, but patients with major depressive disorder have been found to have higher levels of circulating pro-inflammatory cytokines.
While there is still so much to learn and science is only just beginning to get to grips with it, what can be asserted with some confidence is that healthy and diverse gut bacteria are important for good mental health.
10 ways to optimise your gut health for mental health
Roberta Baldo, Nutritional Therapist says: “The gut-brain connection is so important that trying to treat poor mental health without one eye on nutrition can be an uphill battle. Of course, when you are not feeling mentally well, the last thing you feel like doing is cooking complicated meals. But there are simple, easy ways to get healthy, gut-friendly whole foods into your diet, little by little.”
Here are 10 ways to look after your gut microbiome:
- Take a good quality probiotic supplement to promote gut health by seeding the growth of healthy bacteria (lactobacillus plantarum, lactobacillus rhamnosus, bifidobacterium longum, and lactobacillus helveticus) with a simple capsule or drink.
- Eat fermented foods such as kimchi, yogurt, kefir and sauerkraut which all boast probiotics within them, boosting good bacteria while helping reduce harmful microbes in the gut.
- Eat a broad spectrum of (healthy) foods to encourage diversity within your gut microbiome.
- Get plenty of fibre which you can find in fruit, vegetables, legumes (chickpeas, the various bean types) and nuts and seeds (which also boast healthy fats that are good for the brain).
- Avoid artificial sweeteners in diet drinks and many ‘sugar-free’ options because there is evidence they can damage good bacteria in the gut and the gut wall.
- Eat whole grains like oats, millet and quinoa. These boast beneficial carbohydrates such as beta-glucan which are well-digested by gut bacteria and they also have lots of fibre.
- Eat plenty of prebiotic foods such as asparagus, apples, oats, artichokes and bananas. Prebiotics are a kind of fibre that promote the development of healthy bacteria.
- Only take antibiotics when you have to. Antibiotics are very effective at killing bacteria – so good that they kill both the good and the bad, including in your gut microbiome. To look after your gut microbiome and avoid antibiotic resistance, only take antibiotics when you really need them.
- Eat polyphenol-rich foods such as dark chocolate, whole grains, olive oil and green tea. Polyphenols are plant compounds that when broken down by the gut, help to promote the growth of healthy bacteria.
- Avoid ultra-processed foods such as crisps, fast foods, and most multiple-ingredient frozen foods, because there is evidence they can be harmful to gut health. If you don’t want to spend your life looking up ingredients in the supermarket, there are apps you can download to scan barcodes. But a good rule of thumb is to avoid buying foods with multiple ingredients and stick to a ‘one food=one ingredient’ approach.
Here at The London Psychiatry Centre we know that mind and body are intricately connected and we’ve been at the forefront of biological psychiatry for some time. In addition to some of the UK’s finest mental health professionals, our team includes cardiologists, endocrinologists and expert nutritionists. Taking a ‘whole body, whole person’ approach to mental health, we can offer video or telephone consultations from anywhere in the UK. To find out how we can help, contact us today:
