The human condition is not something many of us ponder until something goes wrong upstairs. Whether it be within our own psyche or that of a loved one, mental illness can be a black hole of unknown dimensions adversely effecting lives. Things like anxiety and depression are often frightening due to their impact upon relatively unexplored realms. Our minds are vast repositories of memories, thoughts, feelings, and sensations (Florey, 2021). When things go wrong in our lives, we can slip into a scary world of dark shadows seemingly immune to the warmth of the sun. Beyond Blue reports that anxiety is the most common mental health issue in Australia, with one in four experiencing it at some point in their lives. Therefore, the idea that these frightening states can be influenced by the trillions of tiny creatures inhabiting our gut is immediately arresting and thought provoking.

Microbiome: Our New Understanding

It seems we are not truly alone in the greater scheme of things. Rather, we have, until now, neglected to look down and within. We are host to a colony of microbes called our microbiome (Berg, 2020). These trillions of bacterial cells located mainly in the colon are connected via the vagus nerve to the brain. The microbiome directly influences the production of important neurotransmitters, which are involved in mood-promoting chemical activity. Our understanding has come a long way since Sigmund Freud was getting patients to recline on his couch and talk about their feelings toward their parents. We are beginning to comprehend the vastness of what it means to be a sentient biological life form on planet earth.

The Anxiety Link

Some health writers have introduced the microbiome link to feelings of anxiety in human beings via those sensations of having butterflies in your tummy and/or feeling slightly nauseous prior to doing something like public speaking. This connects our body and its sensations to those feelings often placed in the intangible basket. We experience these psychological conditions in the physiology of our bodies. Stress manifests in our guts and affects our microbiome. Many people find it difficult to eat when they are very nervous. The Brain Derived Neurotrophic Factor (BDNF) is a key molecule intrinsically involved in the plasticity of the brain as it relates to learning and memory. Healthy BDNF expression is anathema to mental disorders like anxiety and depression. Therefore, its role in regulating emotions and cognition via the Hypothalamus-Pituitary-Adrenal-Axis (HPA) is a crucial one (Dwivedi, 2009). A healthy diverse microbiome reduces pro-inflammatory cytokines and regulates the HPA axis.

Neuroscience & Nutritionists

Neuroscience and nutritionists are pulling together to provide a clearer and more inclusive view of the human condition (Zamroziewicz, 2016). Anxiety and depression influenced by the microbiome no longer appears a completely unlikely affair. The connection between the bottom and the top is not such a distasteful marriage as was once thought by those responsible for their specialised departments in the citadel of medical science. Everything is connected, it seems, in a holistic web and reductionist scientific theories are a thing of the obsolete past. How you feel is not a mere matter of your thoughts, experiences, and beliefs. Why you may be anxious or depressed is no longer confined to nurture issues but is directly influenced via a much broader biological palette.

We Are What We Eat

We are what we eat. You may have heard this refrain in the singular or the plural. The truth of this statement grows daily with our more nuanced understanding of our own biology and that of the world in which we live. Our discovery of DNA and our technological advancements in being able to read these codes have expanded our awareness of the biological universe in which we live. We are so much more than we first thought. Metabolism, which turns food into energy, involves trillions of these microbes in our gut, which are not essentially human cells but co-opted bacteria doing what they love. The types of foods we eat determine the make-up of our microbiome and these play their part in digestive inflammation and the permeability of the gut lining. If you eat a lot of highly processed foods, full of sugars, fats, etc you will attract the gut bacteria that breaks down these elements to the exclusion of health inducing microbes. Although everyone has a unique microbiome, they can be categorised into three distinct enterotypes based on which species of bacteria dominate. Prevotella species enterotype is associated with a diet high in carbohydrates. A high protein-based diet will have a Bacteroides species enterotype (Clapp, 2017).

Macro & Micro Effects of Dietary Neglect

It is interesting to ponder the above so below paradigm. Consider the capitalist free enterprise system, as successful agents within this market their branded fast foods to you via advertising through the media. You consume their products in response to this input on your devices. In the macro world your affirmation of their brand delivers success and revenue so that they can increase their marketing and reach. They want you to eat the same things all the time, their products, which makes them more money. Fast foods are cheap, readily available, and constantly marketed to the general public. Inside of you a similar thing occurs, as your microbiome is shaped by your diet high in these highly processed foods. The gut bacteria which feed on these sugars and fats hunger for more at the expense of those bacteria wanting fibre, which die off. The microbiome then suffers from dysbiosis, which means balance and stability wanes due to a lack of gut bacterial diversity (Clapp, 2017). Lower levels of the short chain fatty acid butyrate stimulate inflammation. Inflammation is a direct cause of depression in human beings. Eating a fast food diet of the same highly processed foods is bad for your health and negatively impacts upon your mental health. There is a vicious cycle at play here, which is costing our communities billions of dollars in health expenditure and a great deal of unhappiness for individuals suffering from mental health disorders. Something to think about when you next watch one of those bright and bubbly commercials for the plethora of fast food outlets here in Australia.

Poor diets are inextricably linked with a multitude of negative health outcomes, which we are now finding include conditions like anxiousness and depression. Large companies own many of the franchises for fast food operations locally and globally. Obesity, and childhood obesity, are major problems for western nations like Australia and the United States (Jolly, 2010). The fast food industry spends hundreds of millions of dollars annually marketing their products in Australia. In comparison you would be hard pressed to find any ads for fruit and vegetables on any of the high traffic media channels in this country. Human beings are psychologically drawn to images showing smiling faces and bright shiny things (Fennis, 2020). Fast foods and sugary soft drinks are always advertised in association with these elements. Fast foods promise good times and immediate flavour hits via sugar, salt, caffeine, and fats. They are easy to consume and involve no work on behalf of the consumer. Fast foods are heavily marketed toward children with childlike imagery including clowns, cute animal cartoons, and lots of high energy scenes. Advertisements featuring these products portray fun things and happy times for those consuming these fast foods in their bright and colourful packaging. Everything is made easy for the consumer, and they are encouraged to eat a diet rich in these fast foods. We now know that the party cannot last and that a diet rich in these highly processed foods is a recipe for mental health issues like anxiety and depression in addition to the very real dangers of obesity.

We Eat Fibre for Our Microbiome

Something to remember is the fact that we eat fibre not for our own nourishment but for the gut bacteria inside of us. The many trillions of microorganisms that feed on fibre do so to power themselves to do all the essential metabolic functions we need them to do. We are not alone, and we need to feed our colonies of gut flora with the right stuff – fibre. What is fibre? Fibre is the indigestible element of plant foods (NHMRC, 2006). This plant fibre can be sourced from fruits, vegetables, grains, nuts, seeds, and legumes. Recent studies are identifying new sources of plant fibre, which provide higher prebiotic qualities to boost microbiome diversity (Comino, 2018).

It takes some time for new information and discoveries to reach a wider audience. The biological revelations regarding the gut brain axis are starting to filter their way down to the general public. YouTube is a portal for a plethora of video presentations explaining the connection between our microbiome and our brains. Many medical scientists, nutritionists, and psychiatrists are sharing the exciting findings for their fields from this ground-breaking new understanding. Various studies have shown changes in gut bacteria when accompanied by stress related psychiatric disorders (Wilmes, 2021). Irritable Bowel Syndrome (IBS) is often associated with psychiatric conditions involving anxiety and depression in patients observed in these studies. This research finding suggests the potential for utilising treatments that target the microbiome in the management of these mental health conditions. Rather than treating the symptoms with the usual chemical arsenal designed to alleviate them, some psychiatrists are exploring therapeutic options in relation to the microbiome.

Key points to consider are that our microbiome can engender a range of neuroactive molecules which influence our mood, behaviour, and cognition (Wilmes, 2021). Neurotransmitters like serotonin, GABA, and noradrenaline are functioning in both the gastrointestinal and brain regions. Serotonin is produced from the precursor tryptophan, which is an essential amino acid. Our microbiome directly modulates our levels of tryptophan and its metabolites. Low levels of serotonin are a key indicator in clinical depression. Research has found a preponderance of particular gut bacteria shows up in depressed patients. These include the numerous species of the genus Bifidobacterium, which are B. adolescentis, B. dentium, and B. longum. A diverse microbiome is healthy and in contrast when increased levels of certain gut bacteria eventuates it is a bad sign for the health of that individual. Inflammation within the body is the cause of numerous health issues and disorders. In patients with IBS, the metabolic products of the Lactobacillaceae and Bacteroides strains are thought to cause bloating and inflammation. Gamma-Aminobutyric-acid (GABA) is a neurotransmitter which inhibits neural activity inside the brain. GABA has long been associated with depression and other mental health issues. Researchers have discovered that GABA is produced by Bacteroides in the microbiome (Strandwitz, 2019). Studies at Weill Cornell Medicine have shown that patients with less of these bacteria had more prefrontal lobe hyperactivity, which is associated with severe depression. Philip Strandwitz and colleagues have filed a patent for packaging these particular Bacteroides as therapeutic products for the treatment of depression and other mental disorders (Pennisi, 2020). Could this be the beginning of a whole new raft of microbiome related treatments for mental health conditions?

It is the bidirectional communication between our microbiome and our central nervous system, which has turned our understanding on its head. Dysbiosis and gut inflammation are clearly associated with many instances of mental illness like anxiety and depression (Clapp, 2017). Trauma can be a catalyst for mental disorders but its impact upon the sufferer is also observed biologically via the state of the microbiome and related inflammatory gastrointestinal conditions. This can be why sufferers of clinical depression often manifest a range of other negative health issues. Increased intestinal permeability can result in infections and a depressed immune system.

Probiotic and prebiotic treatments are now being considered and employed as therapeutic approaches for anxiety and depression. Probiotics are living microorganisms, usually yeasts and bacteria, which are given as supplements to alter the microbiome of patients. Chronic inflammation has been positively treated with probiotics. Prebiotics are similarly altering the microbiome of patients to treat a range of mental health conditions (Ansari, 2020). Understanding the link between the microbiome and our central nervous system is providing more options in the treatment of these mental disorders and associated gut inflammation diseases.

Anxiety and depression are particularly prevalent conditions in our modern world, and we are beginning to comprehend how these mental illnesses are linked to our physiology. New levels of biological understanding have revealed the gut-brain-axis. The importance of maintaining a healthy and diverse microbiome is becoming clearer day by day. We cannot ignore and/or neglect our diet if we wish to remain free of mental health issues over a lifetime. Fibre is an essential component of our dietary input if we are to optimise our wellbeing and feed our microbiome. New therapeutic approaches based on this exciting understanding of our gut health are emerging for those suffering from conditions like anxiety and depression. Positive conclusions can be drawn from this, as it is truly the most ground-breaking discovery in medical science this century. Natural therapeutic approaches based on a deeper understanding of our biology are now available.

Sudha Hamilton is a natural health writer, historian, and chef. His published titles include: House Therapy: Discover Who You Really Are At Home; Healing Our Wellbeing; and Sacred Chef.

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