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It’s no secret that chemical imbalances in the brain are often to blame when it comes to mental illness. The solution should be simple then: correct the imbalance, correct the problem. But what if imbalances elsewhere in the body could also affect the brain? Turns out: they can. Specifically, imbalances in gut bacteria can directly affect mental health. But how, exactly, is there a link between gut health and mental health?

The digestive system, also known as the gut, is physically connected to the brain. The brain connects to the gut via nerves, and sends messages through this link. But what if the brain wasn’t the only one calling the shots?

The gut has its own communication hub called the enteric nervous system (ENS). In fact, it’s often referred to as the “second brain”, and it can send signals too. That’s right, the gut-brain connection is actually a two-way street. The brain can tell the gut what to do, but the gut can send messages that tell the brain what to do. This got researchers thinking: could a problem in the gut signal a problem in the brain?

Let’s take a closer look inside the gut. We all have a community of bacteria called the gut microbiome. Each person’s bacteria profile is unique, like a fingerprint. So, what does it do? The microbiome protects our body against invaders, supports the immune system and makes brain chemicals called neurotransmitters. 90% of the body’s serotonin and 50% of dopamine is made in the gut. These neurotransmitters help us feel happy and content, so we need healthy gut bacteria to feel good mentally. But what if the gut microbiome isn’t working properly?

90% of the body’s serotonin and 50% of dopamine is made in the gut.

Dysbiosis is where things go wrong. Dysbiosis is an imbalance of the gut bacteria. It could be too many bacteria, too little, or not enough diversity between strains. When this happens, the rest of the body is often affected. Research shows a connection between this imbalance and many chronic diseases including: cancer, diabetes, and…. you guessed it: mental illness. A breakthrough study in 2004 compared stress response between two groups of mice. One group had their gut bacteria removed, while the other group’s bacteria were left intact. Results showed a much higher stress response in the mice with no gut bacteria. Other studies show higher levels of anxiety and depression in animals with imbalanced gut bacteria, and improvements when the bacteria are balanced again. Although we need more studies in humans, there is strong evidence that a gut imbalance is linked to mental problems.

But how does a gut imbalance happen, and how can we fix it? Some common causes include: antibiotics, stress, or environmental pollutants. One of the biggest contributors is diet. Diet shapes the gut microbiome, either positively or negatively. The Western diet is often high in refined sugars and unhealthy fats. These types of diets can increase inflammation, and negatively change the gut bacteria. But here’s the good news! We also know what types of foods are good for the gut. Probiotics are healthy bacteria found in many foods like: yogurt, kefir, soft cheeses and fermented foods like sauerkraut, miso and kimchi. Including more of these foods into the diet encourages healthy gut bacteria. Probiotics can also be taken as a supplement. When considering a supplement, look for one with 5-14 strains of bacteria, and 15-225 billion CFUs. Not all supplement brands are the same, so ask your healthcare professional about what’s right for you.

Other ways to keep gut bacteria healthy include: consuming healthy fats like avocado, olive oil and fish; limiting refined sugars, processed foods and saturated fat; and eating more prebiotics. Prebiotics are fibers that the probiotics need to feed on! They can be found in fruits, vegetables, whole grains and flaxseeds.

So, could gut health be the new frontier in treating mental illness? As newer human research emerges, the answer may be yes. But two things are certain: gut and brain are undeniably connected, and the gut is shaped by what we eat. Does a happy gut microbiome equal a happy brain? I guess you’ll have to trust your gut on that one.

The gut and brain are undeniably connected, and the gut is shaped by what we eat.

Dinan, T; Cryan, J. (2012). Regulation of the stress response by the gut microbiota: Implications for psychoneuroimmunology. Psychoneuroimmunology. 37: 1369-1378.
Schneiderhan, J; Master-Hunter, T; Locke, A. (2016). Targeting glut flora to prevent and treat disease. J Fam Pract. 65: 34–8.
Petra, AI; et al. (2015). Gut microbiota-brain-axis and its effect on neuropsychiatric disorders with suspected immune dysregulation. Clin Ther. 37 (5): 984–95.
Mayer, EA; Knight, R; Mazmanian, SK; et al. (2014). Gut microbiomes and the brain: paradigm shift in neuroscience. J Neurosci. 34: 15490–15496.