Good mood food? Exploring the gut-brain connection
The brain and the body have historically been treated as two completely separate entities. However, recent scientific developments have brought to light that not only are the brain and body not separate at all, but they are in fact intrinsically connected. One simply cannot function without the other, with the brain impacting the health and function of the body and vice versa – meaning our bodies have the ability to affect how we think and feel on a daily basis. The hub of all this incredible activity is the gut; the relationship between the gut and the brain is an ever-growing area of research and we now know it has links to essential actions like cognition, memory, motor function and even emotional regulation. What’s even more exciting is that we have the ability to influence both sides of the relationship to improve our mental well-being. Let’s explore the workings of the gut-brain connection…
What is the gut-brain connection?
The gut-brain connection, also referred to as the gut-brain axis, describes the two-way communication system between the gut and the brain. While it was previously thought that the central nervous system (comprising of the brain and spinal cord) was the body’s sole control system, we now know that the gut has its own independently functioning nervous system, called the enteric nervous system[1], often referred to as the ‘second brain’. While it isn’t capable of ‘thought’ like the brain, it is not to be underestimated – as 70-80% of the body’s immune cells are located here![2] The central and enteric nervous systems communicate primarily via the vagus nerve, which sends signals bidirectionally between the two, linking emotional and cognitive centres of the brain with peripheral intestinal functions. If you’ve ever felt butterflies in your stomach before a big event or felt certain about a decision because you ‘feel it in your gut’ – you’ve got the gut-brain axis to thank for that.
Furthermore, a number of important neurotransmitters are produced in the gut. Neurotransmitters are chemical messengers which send signals from a neuron to the next target cell, such as nerve and muscle cells, and they are how the nervous system communicates across the body. Some neurotransmitters, including serotonin, dopamine and norepinephrine (noradrenaline), are essential for emotional regulation and mood, and these are all primarily produced in the gut. It is thought that around 90% of the body’s serotonin is produced here[3]. While much of this is required for gut peristalsis, research has shown it is capable of locally activating nerve endings that are connected directly to the central nervous system, meaning gut-derived serotonin may have a direct impact on mood. Similar findings around the connection between the brain and gut have been replicated in several studies, with poor gut health being linked to low mood, depression, anxiety and even neurological disorders such as ADHD[4].
How can we support the gut-brain connection for good mood?
From the body of evidence currently available, it is clear that the gut plays an important role in how we feel mentally and emotionally. By looking after the gut and keeping it as healthy as possible, it is likely we can positively influence the health of our brain and improve cognition, memory, emotional well-being and overall function. A healthy gut has a strong, integral lining and a diverse and densely populated microbiome[5]. The cells of the gut lining are joined by tight junctions which create a barrier between the outside world and our inside world, helping to filter out pathogens to prevent them from entering the bloodstream. When this barrier is compromised, harmful pathogens are able to effectively bypass the immune cells in the gut lining and pass straight through, activating a body-wide inflammatory response. Chronic inflammation like this has been linked to a number of mental health conditions and low mood states[6]. Additionally, a healthy gut microbiome supports the health of the gut lining by aiding in the production of short-chain fatty acids, the main fuel source for the cells of the mucosal barrier[7]. Maintaining a strong mucosal barrier and a healthy microbiome requires a multi-pronged approach and eating the correct foods can play a major role in this.
Sources of dietary fibre should be included every day, specifically those containing prebiotic fibres, such as whole grains, bananas, greens, onions, garlic, soybeans and artichokes. Prebiotic fibre feeds the beneficial bacteria living in our guts, which produce and release nutrients like butyrate and acetate to strengthen the gut lining. Fibre is also crucial for stool formation and elimination, ridding the body of excess hormones which can promote inflammation by triggering low-grade inflammatory immune responses[8]. Another important dietary component for supporting gut health is probiotics; rather than providing sustenance for the microbiome like prebiotics, probiotics are the healthy live bacteria themselves. Regularly including sources of probiotics in the diet can increase the density and variety of species within the gut microbiome[9]. Traditionally fermented foods, such as sauerkraut, kimchi, kefir, kombucha, yoghurt and miso are the best sources of probiotics. However, the flavours of these foods are not to everybody’s taste. Additionally, fermented foods will contain varying strains and levels of probiotics, depending on their preparation methods. In these cases, a probiotic supplement may be a suitable alternative; our pro-otic capsules contain 4 well-understood strains of Lactobacillus and Bifidobacterium, with 3 billion active cultures per capsule.
While dietary fibre is vital for the gut, other nutrients also play important roles in maintaining gut integrity, supporting its overall function and ability to produce essential nutrients and neurotransmitters. For example, omega-3 fatty acids, found predominantly in oily fish and some plant foods (to read more about vegan omega-3, click here) help to reduce inflammation, which has a positive effect on the gut through immune system modulation[10]. Studies also suggest omega-3 can positively influence microbial diversity, independent of dietary fibre intake[11].
Staying happy and healthy
Remember – the gut-brain connection is bidirectional, so along with eating the right foods, supporting it from the brain down is also vital for staying happy and healthy. Continuous stress and lack of sleep (which is perceived as stress by the body) increase cortisol levels, which can cause an imbalance of the gut microbiota, so creating effective sleep routines and practising stress management techniques should be a priority for gut and brain health. To read about how the natural herb ashwagandha may support both stress and sleep, click here. Daily movement increases blood flow to the gut, aiding motility and supporting waste excretion. Finally, don’t forget about good old-fashioned water! As humans are around 60% water, staying properly hydrated is essential for every aspect of health – including the gut and brain.
References
[1] Arbab, M.H. (2023) ‘Interaction between gut microbiota and Central and enteric nervous systems: The gut–brain axis concept’, The Gut Microbiota in Health and Disease, pp. 169–178. doi:10.1002/9781119904786.ch15.
[2] Wu, H.-J. and Wu, E. (2012) ‘The role of gut microbiota in immune homeostasis and autoimmunity’, Gut Microbes, 3(1), pp. 4–14. doi:10.4161/gmic.19320.
[3] Butler, M.I., Cryan, J.F. and Dinan, T.G. (2019) ‘Brain–gut–microbiota axis in mood and cognition’, Lactic Acid Bacteria, pp. 463–484. doi:10.1201/9780429057465-28.
[4] Barrio, C., Arias-Sánchez, S. and Martín-Monzón, I. (2022) ‘The gut microbiota-brain axis, psychobiotics and its influence on brain and behaviour: A systematic review’, Psychoneuroendocrinology, 137, p. 105640. doi:10.1016/j.psyneuen.2021.105640.
[5] Amoroso, C. et al. (2020) ‘The role of gut microbiota biomodulators on mucosal immunity and intestinal inflammation’, Cells, 9(5), p. 1234. doi:10.3390/cells9051234.
[6] Jones, B.D. et al. (2020) ‘Inflammation as a treatment target in mood disorders: Review’, BJPsych Open, 6(4). doi:10.1192/bjo.2020.43.
[7] Régnier, M. et al. (2021) ‘Gut microbiome, endocrine control of gut barrier function and Metabolic Diseases’, Journal of Endocrinology, 248(2). doi:10.1530/joe-20-0473.
[8] Myhrstad, M.C. et al. (2020) ‘Dietary fiber, gut microbiota, and Metabolic Regulation—current status in human randomized trials’, Nutrients, 12(3), p. 859. doi:10.3390/nu12030859.
[9] Bda (2022) Probiotics and gut health, Probiotics and gut health | British Dietetic Association (BDA). Available at: https://www.bda.uk.com/resource/probiotics.html (Accessed: 28 September 2023).
[10] Costantini, L. et al. (2017) ‘Impact of omega-3 fatty acids on the gut microbiota’, International Journal of Molecular Sciences, 18(12), p. 2645. doi:10.3390/ijms18122645.
[11] Fu, Y. et al. (2021) ‘Associations among dietary omega-3 polyunsaturated fatty acids, the gut microbiota, and intestinal immunity’, Mediators of Inflammation, 2021, pp. 1–11. doi:10.1155/2021/8879227.
