What is the Gut-Brain Axis?
Have you ever felt butterflies in your stomach when you’re nervous? Or ever felt the need to run to the bathroom right before you leave to go for a job interview? Thankfully there is an explanation for this! The link or communication pathway between your gut and your brain, also known as the gut-brain axis is what causes this to occur. This communication pathway is bidirectional, so it works in two directions. This means that your brain and how you are feeling can influence your gut activities (hence the nervous poos), and what is happening inside your gut can have an effect on your brain, generating particular feelings, emotions, thoughts and even behaviours.
How Does This Gut-Brain Axis Work?
Neurons or chemical transmitters are the main communicators and their role is to send information up and down the vagus nerve, which connects the gut to the brains limbic system (home of the emotions and stress in the brain). So, these neurons are regularly going back and forth sending these messages between the two systems, keeping them in contact.
The gut and brain are constantly in communication with one another and this line of communication is a rather convenient way for your gut to keep the brain up to date with your overall health. Research also suggests that your gut microbiome also plays an important role in the gut-brain axis.
The Gut Microbiome & the Gut-Brain Axis
Trillions of microbes or bacteria live throughout the body, all having various roles, with around 90% of these living all throughout the gut! Primarily, the gut microbiome plays important roles in digestion, production of hormones (to transmit messages!) and protection against pathogens, which are bacteria, viruses, or other microorganisms that can cause disease.
Each of our individual gut microbiome’s vary, with a large range of influencing factors, all starting from the moment we are born! For example, a vaginal birth means that you were exposed to the bacteria in your mother’s birth canal, immediately gaining exposure to a range of different species. Whereas a caesarean birth means you were exposed to bacteria located on the skin and less exposure to these varied species. Therefore, the diversity of gut bacteria is lower in infants born via caesarean section and the composition of their gut microbiome is different to those born vaginally. Fortunately, how you are born is not the only factor influencing the make up of your gut microbiome! There are so many more factors influencing the variety you have, including where you live, your work/home environments, who you are in contact with each day and most importantly, what you eat!
A wide variety of gut bacteria means a wide range of hormones being produced by the microbiome including serotonin (happy hormone) and dopamine (the hormone stimulating learning and memory). Once the microbiome releases these hormones, they are transported through the vagus nerve, stimulating the brain, which improves mood and memory. This helps to explain the link found between the diversity of the gut microbiome and its influence on anxiety and depression. Research suggests that a disturbance and reduced diversity of gut bacteria can have a link to increased feelings of anxiety and depression, with less of the serotonin and dopamine being produced.
Impact on Our Health & The Important Role of Nutrition
There are so many factors influencing the diversity, or the variety of different types of gut bacteria, in our gut microbiome. However, it is important to acknowledge that out of all these things, diet is the one factor that we can easily manipulate to help improve the diversity of our bacteria. Since a large portion of the microbiome is found in our gut, the types of foods we eat can influence their diversity.
The types of food that we eat and the nutrients that they contain can have a large influence on not only our gut bacteria, but the gut-brain axis overall, with studies linking our diet to our mental awareness, cognition, moral principles and our emotions. Variation is key! Research is still in its infancy, however studies involving dietary changes to positively influence the gut microbiome have shown many positive changes to mental health. So, in other words, the more variety in your gut microbiome, the happier you are!
The Gut-Brain Axis & Irritable Bowel Syndrome
As we now know, our gut and brain are constantly in communication with one another and when something goes wrong with one, the other reacts. Unfortunately, this is the case with people with irritable bowel syndrome (IBS) and is a perfect example of how the two systems communicate and influence each other. Research in this area is much more associated with animal studies rather than humans however, a significant link has been found between the gut microbiome, the gut-brain axis and in turn IBS symptoms, with significant links between stress and the gut microbiome response. Reality is, there is a link between IBS and stress/anxiety with stress reducing the diversity of the gut microbiome overall, increasing inflammation within the gut (with less production of those happy hormones).
How Can Food Help the Gut-Brain Axis?
Studies suggest that including probiotics and prebiotics in the diet can help in improving the diversity of gut bacteria with abnormal gut function improving when these foods are included in the diet.
Prebiotics are a form of fibre that passes through the digestive tract and into the large intestine where the good bacteria feed off the prebiotic, producing by-products that positively stimulate the gut-brain axis. Therefore, prebiotics have a large role in improving the diversity and the actions of the bacteria in the gut and in turn, the brain.
Probiotics, however, are the good gut bacteria already present in our body which have also been added into foods such as yogurt, kefir and even supplements. Currently the research available does suggest that there is a potential for health benefits with enough present in the gut, however we are currently unsure if probiotics consumed in the form of foods and supplements can survive the journey through the digestive system, suggesting they may not have extensive health benefits.
So overall, it is recommended a diet with a wide variety of high fibre foods (prebiotics), vegetables, fruit and grains with the inclusion of dairy products like yogurt and milk, can help to increase the diversity of the gut microbiome to stimulate positive activity in the gut and therefore the brain.
Why Should You Know About the Gut-Brain Axis?
The phrase “gut feeling” gets thrown around quite a bit, however, is an important concept. What you’re eating and how you’re feeling can often be interrelated, which most people are not aware of. If you do not have an overall varied and healthy diet, this may have an influence on the way you think or feel and can result in feeling fatigued, “cloudy” or emotional. This might be your gut-brain axis feeding back to you! If you think this might be the case, book in to see a dietitian, who can help you improve your overall diet and gut health.
Start Improving Your Gut Microbiome Now with These Simple Steps!
Choose a wide range of different fruits and vegetables daily! Remember to try to incorporate 2.5 cups of vegetables and 2 pieces of fruit daily.
Increase your intake of fibre by including more prebiotic foods into your diet! (See below for some suggestions).
Include a wide range of wholegrain foods into your diet! Remember, the more seeds and grains, the better.
Introduce omega 3 fats! Think about incorporating more oily fish into your diet and try to do so at least 2 times per week.
Don’t be afraid to try new foods! Perhaps a food you’re considering trying may have a positive effect on your gut microbiome or introduce a new strain!
Examples of Prebiotic Foods to Help Improve Your Gut Microbiome!
Garlic
Onion
Bananas
Soybeans
Red kidney beans and other legumes
Grapefruit
Rye
Bran Cereals
Oats
Cashews
If you're feeling stuck and would like to learn more about how I can help you break free from the cycle of discomfort and unpredictability of living with IBS, CLICK HERE to book a Complementary Strategy Call and let's chat about your journey to finding lifelong relief and reclaiming your confidence and control over your IBS!
Written by Stephanie Monacella
Steph is a final year student dietitian completing her last two weeks of the Masters of Dietetics course at Deakin University. “I am very passionate about using my knowledge and skills that I have learnt to provide the public with nutrition related content from the most up to date scientific evidence-based research.”
References
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Martin C, Osadchiy V, Kalani A & Mayer E (2018). The Brain-Gut-Microbiome Axis. Cellular and Molecular Gastroenterology and Hepatology. 6(2):133-148.
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Monash University Department of Gastroenterology. Prebiotic Diet – FAQs [Internet]. Cited 2019 June 6. Available from: https://www.monash.edu/medicine/ccs/gastroenterology/prebiotic/faq#3
Oriach C, Robertson R, Stanton C, Cryan J & Dinan T (2016). Food for thought: The role of nutrition in the microbiota-gut–brain axis. Clinical Nutrition Experimental. 6:25-38.
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