Dr. Oscar Coetzee: How Your Gut Bacteria Affect Anxiety, Depression & Mental Health
Audio only version
Show Description
Anxiety, depression and chronic stress are usually approached through psychology and the brain – but what if some of the biological processes influencing our mental health begin much further down, in the gut?
In this episode of the MindHealth360 Show, I sit down with Dr. Oscar Coetzee, clinician, researcher and educator working at the intersection of psychology and nutritional science, to explore the gut–brain connection, the microbiome and the nutritional foundations of mental health.
Dr. Coetzee explains how the bacteria living in our gut can influence inflammation, nutrient metabolism and the amino acids needed to make neurotransmitters and why he believes gut and nutritional health deserve greater consideration alongside psychiatry and psychotherapy.
Together, we explore the role of anaerobic keystone bacteria, what can happen when beneficial microbial communities are depleted and how increased gut permeability and LPS-producing bacteria may contribute to systemic inflammation and neuroinflammation. We also look at factors that may disrupt this system, from chronic psychological stress (which can affect both nutritional requirements and our ability to digest and assimilate nutrients) and constant digital stimulation, to diet, alcohol, medications and environmental exposures.
Dr. Coetzee’s message is not simply to take more probiotics or supplements. Instead, he makes the case for a more personalised approach that takes into account the gut, nutrition, metabolism and individual biology alongside psychological and psychiatric care. In this way he brings together psychiatry, therapy and what he calls psychonutrigenomics together as three complementary pillars of mental health care.
In this episode, you’ll learn:
- How gut health and mental health are interconnected and how the microbiome can influence inflammation, nutrient metabolism and neurotransmitter pathways.
- Why anaerobic keystone bacteria such as Akkermansia, Roseburia and Faecalibacterium prausnitzii are receiving increasing attention.
- How the loss of beneficial anaerobic bacteria may allow opportunistic, LPS-producing bacteria to proliferate and contribute to inflammation and neuroinflammation.
- How psychological, physiological and environmental stress can trigger the body’s stress response and how chronic activation can deplete nutrients and impair digestion.
- How information overload and constant digital stimulation are underrecognised drivers of anxiety.
- How amino acids including tryptophan interact with blood sugar regulation, B vitamins and magnesium in pathways involved in neurotransmitter production.
- Why simply taking nutrients may not solve the problem if the gut cannot digest, absorb and assimilate them effectively.
- Why Dr. Coetzee believes mental healthcare should integrate psychiatry, therapy and psychonutrigenomics rather than considering them in isolation.
- How functional testing may help clinicians investigate the microbiome, nutrient status, metabolism and genetics as part of a more personalised assessment of mental health symptoms.
About Dr. Oscar Coetzee
Dr. Coetzee is a dedicated, dynamic nutritionist, published author, researcher, educator, ranked professor, and nationally renowned speaker. He has been a pioneer in the field of nutritional science and research for more than 25 years. Dr. Oscar Coetzee holds a bachelor’s degree in psychology, dual master’s degrees in organizational psychology and human nutrition, and dual doctorates in holistic nutrition and clinical nutrition.
Show Notes
Take the conversation further at IMMH 2026
At the Integrative Medicine for Mental Health (IMMH) Conference 2026, Dr. Oscar Coetzee will explore these ideas in greater clinical depth in his session, The Connection Between Functional Testing and Mental Health: A New Frontier of Prevention, Causal Investigation and Treatment, sponsored by Designs for Health.
Dr. Coetzee will explore how functional stool testing, organic acids, metabolomics, hormonal and genomic testing can be used to investigate neurocognitive dysfunction and mental health, including the relationships between nutrient deficiencies, the microbiome, gut inflammation, amino acids and genetic factors involved in neurotransmitter pathways.
His session makes the case for what he describes as the often-overlooked “third pillar” of mental health treatment – psychonutrigenomics – sitting alongside psychiatry and therapy/counselling.
Join Dr. Coetzee and more than 50 leading clinicians and researchers at IMMH 2026, October 8–11 at the Town and Country Resort, San Diego – or online.