Exploring the hidden pathways between gut health and the brain. Let’s deep dive into the microbial mind as recent studies are uncovering the intricate pathways that connect gut health to brain structure, function and even our risk for neurological and mood disorders. Read on to discover how your microbiome influences memory, mood and more.
Scientists have discovered that the human body is home to tens of trillions of microbes, including bacteria, viruses, and fungi, that inhabit nearly every surface and cavity, from the skin and mouth to the gut and beyond. While the gut microbiome has received the most attention for its profound influence on health, recent research has begun to explore the possibility that microbes may also be present within the brain itself, challenging the long-held belief that the brain is a sterile environment1.
“All disease begins in the gut” - Hippocrates
Emerging studies have identified a diverse range of bacteria, viruses and fungi in the brains of patients with neurodegenerative diseases such as dementia1. However, this remains a topic of ongoing scientific debate and investigation. Understanding the diversity and roles of these microbial communities, both in the gut and potentially in the brain, could lead to new avenues for investigating brain health, ageing, and disease.
The gut-brain axis is a complex, bidirectional communication network that links the gastrointestinal (GI) tract with the central nervous system, which includes the brain and spinal cord. This connection allows the brain to influence gut function in response to stress and emotions, as reflected in the saying "butterflies in your tummy."
The gut microbiota can regulate brain activity through immune, neuroendocrine, and vagal nerve pathways. Recent research has increasingly supported the idea of the gut as a "second brain," with the microbiome playing a crucial role in modulating behaviours, cognition, and emotional responses. Disruptions in this axis have been associated with a range of neurological and psychiatric disorders, highlighting the importance of maintaining a balanced gut ecosystem for overall brain health2.
The 'Psychobiome' is a term used to describe the community of gut microbes that communicate with your brain, significantly influencing your mood, stress and mental health3.
In a 2019 study led by Dr. Sara Vieira-Silva, researchers analysed the gut bacteria of over 2,000 individuals from Belgium and the Netherlands to explore a potential link between gut microbial composition and depression4. They employed advanced genetic sequencing techniques and found that individuals with depression consistently lacked two specific types of gut bacteria: Coprococcus and Dialister. This pattern was observed regardless of whether the participants were taking antidepressants. The findings were validated in both the Belgian and Dutch groups, as well as in a separate group of clinically depressed patients, making this the most comprehensive and robust human study on the topic to date4.
Are these missing bacteria important?
These bacteria have been linked to production of substances that may help reduce inflammation and support brain health, which could explain their link to better mood and quality of life.
A recent review paper published in January 2025 in Cureus examined 15 studies and found that individuals with depression consistently have less diverse gut bacteria and higher levels of inflammation5. Beneficial, anti-inflammatory bacterial species, such as Lactobacillus, are often scarce in these individuals5.
This raises important questions: does this imbalance in gut bacteria (known as dysbiosis) contribute to brain inflammation and disrupt mood-regulating neurotransmitters?
The good news is that the studies indicated that combinations of probiotics, fibre-rich diets, or fermented foods could improve depressive symptoms, sometimes as effectively as traditional antidepressants.
However, it is important to exercise caution regarding the evidence as most of these studies are observational rather than randomised controlled trials. This means they cannot definitively prove whether changes in gut bacteria cause depression or if the reverse is true. Additionally, the methods used in the studies varied widely - some employed advanced genetic sequencing, while others relied on older techniques, making direct comparisons difficult. Sample sizes also varied, ranging from just 50 to 600 participants, and participants' diets and lifestyles were not always controlled. While probiotics show promise, we still do not know which strains or dosages are most effective in the long term5,7.
‘The Gut-Brain axis is a highway, but we’re still mapping the exits!’
We have all heard of probiotics and sometimes even the term prebiotics but what about psychobiotics? These are considered beneficial bacteria that improve mental health by reducing inflammation, modulating stress responses and enhancing nutrient absorption.
Recent research demonstrates that making comprehensive lifestyle changes can enhance cognitive function in individuals with early Alzheimer's disease. Additionally, these changes positively affect the gut microbiome by promoting a healthier balance. Specifically, they increase beneficial bacteria that are associated with a reduced risk of dementia while decreasing harmful microbes linked to inflammation and cognitive decline6.
Caring for your gut may help protect your brain as you age!
Emerging research reveals that gut microbiome changes can precede detectable brain pathology in neurodegenerative disorders by years in humans and months in animal models, acting as potential early warning signs for diseases such as Alzheimer’s and Parkinson’s6.
Dr Dean Ornish and colleagues published a landmark randomised, controlled clinical trial in Alzheimer’s Research & Therapy8.
This recent study revealed that a comprehensive lifestyle intervention – without the use of any medications – significantly improved cognitive function and daily activities in individuals with early dementia and Alzheimer’s disease. This intervention included a plant-based diet, moderate exercise, stress management, and social support. It is the first rigorous clinical evidence indicating that substantial lifestyle changes alone can slow or even reverse cognitive decline in the early stages of Alzheimer’s, providing new hope for patients and their families.
Although the gut microbiome was not the primary focus of the study, changes in gut microbiome composition were specifically noted. The researchers found that only the intervention group – those who participated in the intensive lifestyle changes – exhibited significant improvements in their gut microbiome (p < 0.0001), while the control group did not show such changes. The intervention group experienced increases in beneficial bacterial types like Blautia and Eubacterium, which are associated with a lower risk of Alzheimer’s disease. Conversely, there was a decrease in harmful bacteria such as Prevotella and Turicibacter, which have been linked to a higher risk of Alzheimer’s and relevant biological processes like serotonin production.
It is important to note that this study’s intervention lasted 20 weeks, so long-term cognitive outcomes have yet to be assessed. The data included 51 participants, drawn from an initial pool of 1,500 individuals. Furthermore, not all participants in the intervention group showed improvement, indicating variability in individual responses.
Faecal Microbiota Transplantation (FMT) is emerging as a promising experimental therapy for Parkinson’s disease (PD), with recent trials showing mixed but intriguing results10.
A 2024 trial demonstrated that FMT from healthy donors improved motor symptoms in PD patients by ~15–20% after 12 months, likely by restoring Prevotella and reducing inflammation10,12.
The gut microbiome is emerging as a revolutionary tool for early screening of neurodegenerative diseases and depression, potentially offering non-invasive, cost-effective insights into brain health years before symptoms appear11,13.
With ongoing advances, future therapies may include precision probiotics, microbiome-derived drugs, or even faecal microbiota transplantation for neuropsychiatric and neurodegenerative diseases14.
By 2030, may we see:
The gut is a crystal ball for brain health – we just need to learn how to read it.
While challenges remain, the microbiome’s potential to transform screening and prevention is undeniable.
As science continues to unravel the intricate links between the gut microbiome and brain health, the future holds promise for new therapies targeting the gut to prevent or slow cognitive decline, boost mood, and enhance memory. While researchers work toward personalised microbiome-based treatments, there are already evidence-backed steps anyone can take to support both gut and brain8:
For now, nurturing your gut through diet, lifestyle, and mindful habits is a powerful way to invest in a brighter, sharper, and more resilient brain.
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