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The Gut-Brain Axis: The Missing Link in Mental Health

Have you ever wondered why so many expressions like “butterflies in my stomach” or “I have a gut feeling” involve our stomachs and brains? Turns out, it’s not a coincidence. 

Over the years, research has been delving into what we now call the gut-brain axis; essentially, how the gut and brain interact with one another and influence each other. 

Thinking of our gut as a second brain might take a little re-learning to do, but we’ve been experiencing it all along. Just think to the last time you had a gut instinct. Did you trust your gut, and go with what you felt, or did you go against it and choose another path? More often than not, the situation that results in following our gut instinct turns out being the better choice. 

The Gut-Brain Axis

The gut-brain axis (GBA) is a bidirectional link between the central nervous system (CNS) and the enteric nervous system (ENS) of the body (1). The GBA has a complex relationship between the endocrine, immune and autonomic nervous systems (ANS), with a series of indirect and direct pathways. 

Because of its connections with these systems, the GBA allows the brain to influence intestinal function (immune cells, epithelial cells, enteric neurons, smooth muscle cells), which is simultaneously under the influence of the gut microbiota.

Microbiota, often mistaken for microbiome, defines the microbe population in a specific ecosystem (such as the skin or gut – hence, “gut microbiota). Microbiome on the other hand, refers to all microorganisms in or on their host as well as their genetic material (2).

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Recent research has suggested that the microbiome is closely interconnected with the GBA, and plays an important role in the GBA structure (3). 

The microbiome is so significant that the Human Microbiome Project was set up to analyze the relationship between humans and microbes. After finding that the microbiome is approximately 150 times greater than the human genome, scientists started labelling it as a ‘superorganism’. This is an important thing to keep in mind when taking into consideration the amount of marketing that goes into selling antimicrobial disinfectants, soaps and cleaners and the like. Could the rise in these products perhaps coincide with the rise in the number of health issues (both mental and physical) we see today? 

According to research on the diversity of the human intestinal microbial flora, over 75% of the gut microbiota include the bacterial phyla Firmicutes and Bacteroidetes. Why is this significant? These phyla are extremely sensitive to change (4). When we start eating foods like salads that are “triple washed”, making sure our hands are washed with antibacterial soap every second we leave the house, and using toxic cleaners like bleach to ensure every last inch of bacteria is dead, problems start to arise. And not just small problems – big ones. Allergies, autoimmune disorders, mental health conditions (like depression and anxiety), and metabolic disorders could very well be the symptom of an unhealthy gut. And one of the largest studies in the world relating to the gut-brain axis is finding just that. 

The Gut-Brain Axis and Mental Health

The largest study of all time on the human gut has been underway since 2012, and what they’re discovering is remarkable. The study, called the “ American Gut Project”, was founded by three PhDs: Rob Knight, Jeff Leach, and Jack Gilbert. 

The data collection, believe it or not, is voluntarily received by those who pay the scientists to look at their stool (over $99!). They are also required to answer questions including those about their diet and lifestyle. 

The results they’ve collected thus far are quite intriguing. Firstly, they’ve found that people who eat a wider variety of plants have a wider variety of bacteria in their microbiome. While they haven’t stated that it’s necessarily better to have a more complex microbiome, they have noted that those who eat more plant matter have less antibiotic resistance (which is a major bonus). This could be due to the fact that these individuals may be eating less processed and packaged foods that contain animal products with antibiotics. 

Another thing the scientists have discovered is that people who have similar bacterial profiles tend to suffer from the same mental health issues. This includes everything from post-traumatic stress disorder (PTSD) to schizophrenia, depression and bipolar disorder. These four conditions have stood out in the study thus far as having a very strong link to gut bacteria diversity. 

And this isn’t the only study that’s found this link. Other research supports gut-brain axis interactions most notably with anxiety and depressive-like behaviors, with plenty of evidence pointing to specific microbial genes that can regulate neurotransmitter activity (5). The study, called From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways makes note that “gut microbiota could also contribute to the regulation of brain function by influencing tryptophan metabolism.” Tryptophan is an essential amino acid required for serotonin synthesis in the CNS (you know, the chemical in our brains that makes us feel good). Once absorbed from the gut, tryptophan crosses the blood brain barrier and is shuttled off for serotonin synthesis. 

How much tryptophan is available at any given moment is heavily influenced by the gut microbiota. If the gut isn’t fed with enough tryptophan through the foods we eat, we’ll likely experience it through modulation of mood. 

In another study, there was a strong correlation found between functional gastrointestinal (GI) disorders caused by dysbiosis and the subsequent presence of mood disorders (6). Dysbiosis, a microbial disturbance or imbalance in the gut can cause disorders of the GI tract like inflammatory bowel disease (IBD) and ulcerative colitis. In addition, it is well established that diseases like irritable bowel syndrome (IBS) and ulcerative colitis can manifest as a response to psychological and physical stressors that trigger the firing up of the CNS. 

How To Make Your Gut Healthier

The surmounting evidence linking mental health and the gut-brain axis is quite compelling, but the question is – what do we do about it? If you’re wanting to improve the state of your gut, there are some things you need to start doing, and some things you need to stop. Here are some things you can start with today.

1. Start Taking Probiotics

Taking probiotics is one of the best things you can do for your gut (especially if you’ve never replenished your good bacteria stores after a round of antibiotics). Studies have found that taking a high-quality probiotic can actually reduce mental health symptoms, or even reduce the risk of developing them from the start (7). 

One small study published in the journal Gastroenterology found that 64 percent of people with mild-to-moderate anxiety or depression who took a daily probiotic for six weeks had fewer depressive symptoms during that time. This, in comparison to only 32 percent of people who took an inactive placebo, found improvement (8). This study also took brain imaging with functional MRIs, and it revealed that people who took a probiotic had noticeable changes in areas of the brain involved in mood. According to the researchers, “probiotics [have] anti-depressive properties.” And this makes sense, given what we’ve explored above. 

If you’re looking for a high-quality probiotic, check out the brands that I recommend below:

Another way you can get extra probiotics into you is by consuming fermented foods like sauerkraut, beet kvass, kimchi or kombucha. 

Also, don’t forget to nourish and feed the healthy bacteria that you grow with the probiotics by taking prebiotics. If you don’t eat a lot of raw foods, it is recommended to take a prebiotic. The cool thing is, is that taking a prebiotic is as simple as taking something like organic, non-GMO potato starch. Potato starch is high in resistant starch, which feeds our gut bacteria to make sure the bacterial colonies are healthy and strong. 

2. Stop Taking Needless Antibiotics

According to Dr. James Graham from, “antibiotics reduce the numbers and diversity of commensal bacteria, which can allow pathogenic or parasitic microbes an opportunity to thrive (9).” Essentially, if you’ve ever taken a round of antibiotics in your life, your gut microbiome is suffering. I generally advise people to stay away from antibiotics if the condition is not life-threatening and if it can be healed or cured via natural means.

Thankfully, you can help heal the gut by taking some of the recommended probiotics mentioned above. And if you do decide to take a round of antibiotics, always be sure to follow up immediately with a high-quality probiotic.

3. Switch up Your Diet & Lifestyle

Switching to a whole-foods diet that is low or devoid of processed foods is a great way to ensure your gut remains happy and healthy. Including plenty of dark leafy greens, fresh ripe fruit, root vegetables, nuts and seeds into your diet will not only increase the complexity of your gut microbiome, but it will infuse your cells with the nutrition they need to stay calm, happy and healthy. 

Steer clear of things like gluten, processed meats, refined sugar, cooked vegetable oils and dairy. While they might taste good in the mean time, they take a big toll on your health, mentally and physically. 

Article courtesy of By Carly Fraser

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