While food has also always been a big part of all cultures, a way to bring community together, only in recent years has it been given some importance as part of a comprehensive treatment plan for mental health conditions.  

The emerging evidence points to a sophisticated gut brain axis that modulates our mood.  To help us understand why your breakfast is causing depression, let’s dive into the major players of this axis. 

Enteric Nervous System:

Around 200-600 million neurons inhabit our gut from the esophagus to the rectum that is totally separate from your sympathetic and parasympathetic nervous system called the Enteric Nervous System (ENS). Also called the “second brain”, it has the power to work independently of your CNS to carry digestive functions. You can imagine it as a Manager. It not only carries signals to the brain released by the gut after digesting food but also can alter gut microbiota on its own. Different foods and substances have very different effects on the nervous system depending on the receptor they will interact with.  Similar to medications that we tend to view as psychoactive, food itself has the potential to react with various receptors present in the gut such as cannabinoid, opiate , GABA, Serotonin receptors creating various altered mental states. It can also control secretion blood flow, hormone release, motility to the gut as it goes back and forth with the CNS.

The Gut Microbiome:

“You are never really alone.” This does not ring truer if you realize if you have around a 100 trillion little microbes calling your gut their home. These belong to different groups ( akin to different tribes or clans),mostly  Firmicutes and Bacteroides which comprise 75% of the entire microbiome. While most of these microbes are helpful inhabitants producing vitamins, good feel hormones and aiding digestion. There are certain microbes that are not. The ratio of these helpful vs harmful bacteria is highly important and are affected by the food we eat, our physical and mental health among other factors.  These gut bacteria in turn have the ability to modulate gut lining, permeability and the messages it sends to the ENS. While, hepatic encephalopathy is just a more drastic example of how a high protein diet or  bacterial overgrowth can alter the mental state in a susceptible individual; the more subtle, chronic effects tend to get downplayed.  Gut bacteria also have the ability to produce many chemicals that are used by the brain as neurotransmitters such as dopamine, serotonin,GABA. 

One interesting study showed how as little as two hours of stress, maybe at the last exam you gave or the last family get together you had, has the ability to alter your gut flora. Another study showed how changes in the ratio of lactobacillus and streptococcus can result in changes in dopamine levels and may predispose you to Parkinson’s disease and Alzheimer’s disease. There is also a noted positive correlation with butyrate producing bacteria in the gut with higher quality of life. Coming back to our topic, eating the right food amongst other interventions promotes the gut flora we want, that gives neurotransmitters that helps us focus and keep us happy and calm.  

The Food we eat:

Diet exerts a profound influence on the gut microbiota composition, making it a key factor in the gut-brain axis. Consuming a diet rich in fiber, fruits, vegetables, and fermented foods promotes a healthy gut microbiome. On the contrary, a diet high in processed foods, sugar, and unhealthy fats can disrupt the gut microbiota and adversely affect mental health. For example, fiber and prebiotics are essential for promoting the growth of beneficial gut bacteria. They serve as nourishment for gut microbes, aiding in the production of short-chain fatty acids (SCFAs), which have anti-inflammatory and neuroprotective effects. A diet abundant in fiber and prebiotics supports a diverse and resilient gut microbiota, potentially mitigating symptoms of anxiety and depression. Probiotics can act on these prebiotics which in turn positively influence brain function and reduce symptoms of anxiety and depression. Yogurt, kefir, kimchi, and sauerkraut are excellent sources of probiotics.

To tie it all together, 

As we put the food in our mouth, it activates the ENS and the gut bacteria. Depending on the food we eat, they can generate different types of signals affecting a wide range of function, gut permeability, motility, activation of certain receptors which in turn lead to release of certain neurotransmitters that can lead to different mind states.  The food itself when digested produces different substances which have the potential to be psychoactive and also affect the quality of the gut flora. (Remember we want good little microbes inhabiting our body).  There is overarching evidence to support a more mediterranean or anti-inflammatory diet which consists mainly of vegetables, fruits, nuts and seeds with low to negligible processed carbohydrates and sugars included in the diet. There is also data to suggest the role of different food groups in different mental health conditions and should be part of an individualized treatment plan and part of our medical education to promote the best care of our mental health.