Hippocrates once said that “All disease begins in the gut.” Almost 2500 years later, scientists and doctors have proven this statement to remain true. There is evidence showing the correlation between what someone consumes and the state of their mental health. There are new studies released that show the brain and gut microbiome work in a bidirectional manner (Limbana, Khan, Eskander, 2020) that can greatly impact one’s cognition, stress, depression, and anxiety.
The gut microbiome consists of everything from the mouth to the colon and all of the trillions of organisms that live in between, such as bacteria, viruses, fungi, and cells. Although everyone’s enteric microbiota varies and is individualized, there are still shared and common organisms found in the intestine. The most prominent are Firmicutes and Bacteroides which make up about 75% of the microbiome. A healthy microbiome consists of a diversity of these organisms, and as Erika Ebbel Angle stated in her TedTalk on Your Gut Microbiome: The Most Important Organ You’ve Never Heard Of, a healthy gut means better mental clarity, higher energy levels, better immunity, and better emotional well-being.
The relationship between the gut and brain is coined the gut-brain axis (GBA) and involves the immune, humoral, neural, and endocrine systems. The central nervous system (CNS), the enteric nervous system (ENS), and the hypothalamic-pituitary-adrenal axis (HPA) all communicate in order to monitor and integrate gut functions and to link emotional and cognitive centers of the brain with intestinal functions. (Carabotti, Scirocco, Maselli, Severi, 2015) New data has shown that a disruption in the microbiota homeostasis, known as dysbiosis, can influence anxiety and cause depression-like behaviors, and is even found in some with autism. Dysbiosis can also be seen in functional gastrointestinal disorders (FGID) that are linked with GBA dysfunctions and mood disorders. The disruption of the gut-brain axis can negatively impact the movement of food coming in from the mouth and out of the body, known as intestinal motility and secretion.
Additionally, the disruption of the gut-brain axis can lead to inflammation, which is one of the leading causes of depression. Prolonged neuroinflammation affects brain functions, and can determine one’s mental state and behavior. This can be seen in many of those who have Inflammatory Bowel Disease or IBD. As the symptoms of IBD worsen, more bouts of depression-like symptoms can be seen, perhaps strengthening the argument that the dysregulation of the pathways of the GBA is connected to inflammation, and therefore depression.
In order to mediate an unhealthy microbiome, the consumption of probiotics has been seen to have some beneficial effects. Having a healthy and well-balanced diet can heal the gut and may prove to be beneficial for mental health, mood, and clarity. There are three molecules that are necessary to maintain a healthy gut, and therefore a healthy brain. They are tyrosine, tryptophan, and ILA. Tyrosine is found in almonds, seeds, and edamame and is converted into dopamine and epinephrine. Dopamine is a compound that motivates and propels initiative behavior, and epinephrine is the fight-or-flight hormone. Moreover, tryptophan can be found in foods such as turkey, eggs, and chia seeds, and is converted into serotonin and melatonin. Serotonin is a neurotransmitter known to help boost one’s mood, behavior, and level of happiness, while melatonin is involved in sleep patterns. In addition, Indole-3-Lactic Acid (ILA) is found in fermented foods, such as kimchi, and is converted into Indole Proprionic Acid (IPA) which is one of the strongest antioxidants that breaks down free radicals in the body. Without having various nutrient-dense foods in your diet, dysbiosis may manifest in psychological symptoms such as anxiety, depression, and stress.
The study of the gut affecting mental health is a relatively new field of research, that still needs to be examined a lot closer. For instance, the use of probiotics to heal the gut, although has promising outcomes, still needs more experimentation before it is deemed accurate. Despite the fact that more research needs to be done, the intimately connected relationship between the gut and brain is irrefutable. The saying “You are what you eat,” cannot be completely disregarded and does hold some weight. In the end, it does no harm to try and improve your gut health since it will only benefit your energy, mental clarity, and overall mood and behavior.
Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: Interactions between enteric microbiota, Central and Enteric Nervous Systems. Annals of gastroenterology. Retrieved May 14, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4367209/
Limbana, T., Khan, F., & Eskander, N. (2020, August 23). Gut microbiome and depression: How microbes affect the way we think. Cureus. Retrieved May 14, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7510518/
YouTube. (2019). YouTube. Retrieved May 14, 2022, from https://www.youtube.com/watch?v=B9RruLkAUm8.