The Power of the Microbiome–Gut–Brain Axis.

The microbiome includes all the microorganisms, like bacteria, viruses, fungi, and other tiny organisms, that live in and on our bodies, and their genetic material. These microorganisms inhabit various body parts, including the skin, mouth, gut, and other areas (see our article Understanding Vaginal Microbiome).

Among the human microbiome, bacteria are the most extensively studied and recognised. They play crucial roles in digesting food, maintaining the immune system, and influencing mood and behaviour. Essentially, the microbiome functions as a bustling community of tiny organisms that coexist with us, often in a mutually beneficial relationship.

Estimates suggest that the human microbiome comprises over 1,000 species and more than 7,000 strains of bacteria, though these numbers can vary.

What is the Microbiome–Gut–Brain Axis?

The microbiome-gut-brain axis is a communication network that links the gut microbiome with the brain. It involves complex interactions between the gut's micro-organisms and the central nervous system, using neural, hormonal, and immune pathways. This connection influences various bodily functions, including digestion, mood, and behaviour, highlighting the significant role gut health plays in overall mental and physical well-being. The gut-brain axis refers to the bidirectional communication between the gut and the brain, involving the enteric nervous system (one of the three main divisions of the autonomic nervous system), central nervous system, endocrine system, immune system, and metabolic pathways. Studies suggest that gut microbiota interact with these systems, clearly affecting brain function and mental health.

The Influence of Gut Microbiomes on Mood and Cognition

Research indicates that a healthy gut microbiome can significantly impact mood and cognition. Increasing beneficial gut bacteria can reduce inflammation and cortisol levels, alleviate symptoms of depression and anxiety, lower stress reactivity, improve memory, and reduce neuroticism (a trait that reflects a person's level of emotional stability) and social anxiety. This suggests that beneficial gut bacteria, or probiotics, could be used to deliver neuroactive compounds to the body like serotonin or dopamine. These chemicals influence the function of the nervous system greatly impacting mood, cognition and overall brain function.

Psychobiotics and Their Impact

Psychobiotics are a special type of probiotics, which are live organisms that, when consumed in adequate amounts, can benefit people with psychiatric disorders. These beneficial bacteria produce and deliver neuroactive substances, such as gamma-aminobutyric acid (GABA) and serotonin. These substances play crucial roles in brain function and mood regulation, thereby influencing the connection between the gut and the brain.

While probiotics are broadly defined as live organisms that provide health benefits when consumed in adequate amounts, only a few have been rigorously studied.

Potential of Psychobiotics in Mental Health

Evidence from animal and human studies indicates that administering beneficial microbes can reduce depression, anxiety, and stress, and improve cognition. This opens up the possibility of using psychobiotics to manage various psychiatric disorders. Psychobiotics, such as Lactobacillus and Bifidobacterium strains, can produce neurotransmitters like serotonin and GABA, reduce cortisol levels, and increase oxytocin levels.

It is now evident that the Microbiome–Gut–Brain Axis (MGBA) plays a crucial role in women's health, linking the gut microbiota with brain function and overall well-being. For women, the MGBA is particularly significant due to the complex interplay between gut bacteria, hormonal cycles, and mood regulation. Dysbiosis, or the imbalance of gut microbiota, can lead to conditions such as irritable bowel syndrome (IBS), depression, and anxiety, all of which disproportionately affect women. Furthermore, maintaining a healthy gut microbiome can enhance nutrient absorption and immune function, critical for managing common female-specific health issues such as osteoporosis and autoimmune diseases.

Apart from producing neurotransmitters like serotonin, which are vital for mood stabilisation, the MGBA also impacts hormonal balance. The gut microbiome can, in fact, influence the metabolism of oestrogen, a hormone integral to women's reproductive health. An imbalanced gut microbiota may alter oestrogen levels, potentially leading to conditions like polycystic ovary syndrome (PCOS), endometriosis, and menstrual irregularities. Understanding and supporting the MGBA can thus provide a holistic approach to managing hormonal fluctuations and promoting overall well-being in women.

MGBA therapeutic potential

For women suffering from hormonal imbalance, the MGBA holds significant therapeutic potential. Hormonal imbalances can exacerbate mental health issues such as anxiety and depression, which are modulated by gut microbiota through the production of neurotransmitters and other signalling molecules. By targeting the gut microbiome with probiotics, prebiotics, and dietary modifications, it may be possible to restore hormonal equilibrium and alleviate related symptoms. Additionally, improving gut health can enhance the efficacy of hormone treatments and reduce side effects. This integrative approach not only addresses the symptoms of hormonal imbalance but also targets the underlying mechanisms, offering a comprehensive strategy for improving women's health and quality of life.

Future Directions

Human microbiome research is still in its early stages but shows promise in influencing brain development, behaviour, and mood. The potential to treat mental illnesses such as anxiety, autism, mood disorders, and cognitive disorders with psychobiotics represents an exciting frontier in mental health treatment. Psychobiotics, as non-conventional antidepressants, could offer a novel approach to managing mental health conditions and alleviating symptoms linked to hormonal imbalances in women.

Unfortunately, modern lifestyle factors such as poor diet, high stress, lack of physical activity, overuse of antibacterial products, exposure to environmental contaminants, and frequent use of antibiotics can deplete beneficial microbes. This depletion can negatively impact physical, mental, and emotional health.

In conclusion, understanding the microbiome-gut-brain axis and the role of psychobiotics holds significant potential for revolutionising women's health. By leveraging the body's natural microbial community, we can develop innovative treatments for psychiatric illnesses and effectively manage hormonal imbalances. This holistic approach not only addresses mental health concerns but also promotes overall well-being, paving the way for improved quality of life for women.

Sources:

Psychobiotics and the Manipulation of Bacteria–Gut–Brain Signals – A.Sarkar, S.M. Lehto, S.Harty

Psychobiotics: A new approach for treating mental illness? Snigdha Misra & Debapriya Mohanty