We sometimes say we are sick with worry, that we have butterflies in our stomach, or that we should always trust our gut. These sayings go a lot deeper than just simple intuition, as the gut is deeply connected to the brain through a series of complex, neuronal networks. This unique nervous system found in our gut works both independently from, and in tandem with, the brain, and it has consequently garnered itself the nickname “the second brain”.
The system of nerve cells that has developed in our gastrointestinal tract is considered too complicated to have evolved simply for digestion. The gut has its own set of neurons that allow it to digest food reflexively and independently from the brain, however research indicates our second brain affects more than just digestion –it affects our mental state. Although general gut discomfort may sour our mood, it is likely that our everyday emotional states rely on messages from our organs, with the general health of our gut being a large factor in the general state of our wellbeing.
The gut-brain axis is the term given to the communication network between your gut and your brain. This axis is a key player in our mental health and there is a growing body of research linking diet quality and gut microbiota to the susceptibility of mental illness. This knowledge provides us with a novel and hopeful way to maintain mental health – through our diet.
Diet as an intervention strategy
The emergence of focusing on diet as an intervention strategy against mental illnesses is not a new one, nor should it replace other standard therapies. However, what is changing is our understanding of the mechanisms behind how our diet plays a role in the gut-brain axis. It partially comes down to our gut microbiome – the variety of bacteria housed in our gut – which is the much-needed bacteria that helps us break down food and regulate our immune system. As our diet changes, so does our microbial population, which changes in composition to better suit what we eat. It is believed that the composition of our gut microbiome, as dictated by our diet, is a contributing factor to our mental wellbeing.
Research suggests that as your gut microbiome increases in diversity of bacteria, your mental state reduces in risk of developing ill-health. Simple steps for improving gut diversity can be small lifestyle choices, like a healthy diet, regular exercise, and avoiding smoking. More specifically, food choices like vegetables, legumes, beans, and fruit are strong contenders in maintaining a healthy microbiome, as they are high in fibre which requires bacteria to help digest. In addition, fermented foods enhance the diversity of your gut microbiome and decreases inflammation. These foods include yoghurt, kimchi, sauerkraut, miso, sourdough and kombucha. Foods rich in polyphenols – a plant compound which cannot be digested by humans – are known to reduce blood pressure, inflammation, cholesterol levels, and oxidative stress and increase gut biodiversity. Some foods rich in polyphenols include dark chocolate, red wine, green tea, almonds, onions, blueberries, and broccoli.
The pros of plant-based diets
Some studies have also looked at the impact of plant-based diets on gut biodiversity and mental health. Diets containing animal-based foods promote the growth of different gut bacteria than those found in predominantly plant-based diets, with the latter tending to support a more diverse and stable microbial system. A primarily whole-food, plant-based diet which centres around whole grains, legumes, fruit, and vegetables are fuel for gut bacteria and are associated with lower occurrence of chronic diseases. Research has shown that plant-based diets are protective against mental ill-health such as depression and anxiety, which is in-line with our understanding of diet influencing the gut-brain axis.
This focus on gut biodiversity, while important for the line of communication between the gut and brain, is also incredibly valuable for your overall wellbeing. The gut microbiota is necessary for important physiological functions such as facilitating our metabolism, preventing leaks from the gut, providing effective nourishment, and even producing neurotransmitters. Digestive problems rooted in a lack of gut diversity includes heart burn, gastric reflux, nausea, and constipation, and are all symptoms indicating something is amiss between the gut-brain axis. These illnesses, along with many others, are all linked to inflammation in the gut, which in turn can manifest as poor mental health.
It’s easy to think of the body’s systems as working discretely and independently of each other, but the reality is that our bodily systems are complexly interconnected, with each network affecting the other. The gut-brain axis is a prime example of this, where an imbalance in the gut can contribute to mental ill-health, and likewise mental ill-health can contribute to inflammation. While there is a list of foods and diets that can improve your gut health, the bottom line is, as it often is, to approach your diet and lifestyle with a healthy balance. Incorporate healthy choices and foods into your everyday life, but know that sweet treats and lazy days from time to time will not ruin your progress. Above all, listen to your gut – it’s a lot smarter than you might think.