While "gut health" is a ubiquitous buzzword in the wellness industry, it has historically lacked a clear scientific definition. In this episode, host Dr. Siobhan McCormack sits down with world-renowned expert Professor Maria Marco from UC Davis and the International Scientific Association for Probiotics and Prebiotics (ISAPP).

They discuss the new scientific consensus defining gut health, the crucial differences between fermented foods and probiotics, and what we can actually learn from direct-to-consumer stool tests. Plus, Siobhan gets a behind-the-scenes look at a rigorous clinical trial investigating the health impacts of kimchi.

What We Cover:

• Defining Gut Health: How a global expert panel established the first consensus definition, moving beyond just the microbiome to include six complex domains.
• Symptoms vs. Biomarkers: Why you can still achieve "gut health" even with a chronic but well-managed gut disorder.
• The Microbiome Testing Reality Check: The limitations of commercial stool tests and why they currently lack the clinical utility to guide personalized medical treatment.
• Fermented Foods vs. Probiotics: The true distinction between foods fermented for taste and preservation, versus specific live microbial strains proven to deliver targeted health benefits.
• Inside the Marco Lab: A look at the complexities of nutritional science, including an ongoing clinical trial comparing the physiological effects of kimchi to unfermented cabbage.

Scientific References & Further Reading:

• Marco, M., et al. (2025). Consensus panel definition of gut health. Nature Reviews.
• Marco, M., et al. (2026). 'The impact of fermented dairy on gastrointestinal health and associated biomarkers'. Nutrition Reviews.
• Bischoff, S. (2011). "Gut health": a new objective in medicine? Perspective Paper.

This podcast is brought to you in collaboration with the British Society of Lifestyle Medicine.

Disclaimer: The content in this podcast is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or qualified healthcare provider. Never disregard professional medical advice or delay in seeking it because of something you have heard on this podcast.

While we often think of sleep and diet as separate pillars of health, our internal biological clocks and gut microbiome intricately connect them both. In this episode, co-hosts Dr. Siobhan McCormack and Dr. Sheena Fraser dive into the fascinating, bidirectional relationship between circadian rhythms, sleep quality, and gut health.

They discuss how our physiology adapts to 24-hour light and dark cycles, the metabolic havoc caused by social jet lag and shift work, and how our gut microbes actually operate on their own daily schedules. Plus, Siobhan and Sheena share practical, evidence-based chrononutrition strategies and explore how targeted dietary patterns, probiotics, and fermented foods can significantly boost your mood and sleep architecture.

What We Cover:

The Circadian Symphony: How light, dark, and our body's internal peripheral clocks orchestrate everything from hormone release (like cortisol and melatonin) to digestion.

Sleep Architecture & Mental Health: The critical role of REM and deep sleep, and how just one night of sleep deprivation increases impulsivity and degrades mood.

Chrononutrition: Why when you eat is just as important as what you eat, and how meal timing acts as a major environmental cue for your gut microbes.

Social Jet Lag & Shift Work: The metabolic consequences of disrupted sleep cycles, including increased risks for Type 2 Diabetes, and actionable strategies to regain circadian balance.

Nutrients & Microbes for Sleep: Exploring the science behind specific dietary protocols, the power of Lactobacillus, and how fermented foods support restorative rest.

Scientific References & Further Reading:

• Conti, F. (2025). ‘Dietary protocols to promote and improve restful sleep: A narrative review’. Nutrition Reviews
• Dobielska, M. et al. (2025). ‘Association between fermented food consumption and sleep quality under psychological stress: Prospective cohort study’. Food Science & Nutrition.
• Scott, A.J., Webb, T.L., Martyn-St James, M., Rowse, G., & Weich, S. (2021). 'Improving sleep quality leads to better mental health: A meta-analysis of randomised controlled trials'. Sleep Medicine Reviews
• Hepsomali, P., & Groeger, J.A. (2021). 'Diet, sleep and mental health: Insights from the Uk Biobank Study'. Nutrients
• Reid, M., Omlin, X., Espie, C., Sharman, R., Tamm, S., & Kyle, S. (2022). 'The effect of sleep continuity disruption on multimodal emotion processing and regulation'. Journal of Sleep Research
• Marx, W., Manger, S.H., et al. (2023). 'Clinical guidelines for the use of lifestyle-based mental health care in major depressive disorder'. World Journal of Biological Psychiatry
• Vetter, C. et al. (2018). 'Night Shift Work, Genetic Risk, and Type 2 Diabetes in the UK Biobank'. Diabetes Care

This podcast is brought to you in collaboration with the British Society of Lifestyle Medicine.

Disclaimer:

The content in this podcast is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or qualified healthcare provider. Never disregard professional medical advice or delay in seeking it because of something you have heard on this podcast.

While the gut microbiome often steals the spotlight, the microorganisms residing in our respiratory tract play a vital role in our health and immunity. In this episode, Dr. Sheena Fraser sits down with microbial ecologist Dr. Michael Cox to explore the fascinating, complex, and relatively uncharted territory of the lung microbiome.

They discuss how the lung microbiome fundamentally differs from the gut, the daily flux of bacteria entering and leaving our airways, and the profound impacts of environmental factors like air pollution, smoking, vaping, and household cleaning products. Plus, Dr. Cox shares the massive challenges scientists face when studying these deep-tissue microbes and what the future of respiratory medicine might look like.

What We Cover:

• From Seawater to Sputum: Using marine ecology techniques to decode human respiratory biology.
• Exploring the lungs' dynamic balance of microaspiration and mucociliary clearance.
• Meet the core lung bacteria (Streptococcus, Prevotella, Veillonella) and the puzzle of anaerobes in an oxygen-rich space.
• Environmental Disruptors: How pollution, smoking, and vaping inflame and alter the lung microbiome.
• Hidden Dangers of VOCs: The silent impact of everyday cleaning sprays and aerosols on respiratory health.
• Diet, Exercise, & Epigenetics: The systemic benefits of a high-fiber diet and fitness for chronic lung conditions like COPD and asthma.

About

Dr. Michael Cox is a microbial ecologist and the PGR Lead for the Institute of Microbiology and Infection at the University of Birmingham. His research focuses on the bacteria that reside in the respiratory tract in the context of respiratory diseases (such as COPD and Cystic Fibrosis). His lab works to understand the function of the respiratory microbiome, translate these findings for clinical benefit, and expand our understanding of the respiratory ecosystem beyond just bacteria.

Connect with Dr Michael Cox:

• University of Birmingham

Scientific References & Further Reading:

• Cumming, K. J. (2018). "Long term effects of cleaning on the lungs." American Journal of Respiratory and Critical Care Medicine, 197(9):1099-1101.
• Hussain, S., et al. (2024). "Unlocking the secrets: VOCs and their devastating effects on lung cancer." Pathology - Research and Practice, 255:155157.
• Welsh, H. A., et al. (2026). "The effect of vaping on the human lung microbiota." Inhalation Toxicology, Vol 38, Iss 1.

This podcast is brought to you in collaboration with the British Society of Lifestyle Medicine.

Disclaimer:

The content in this podcast is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or qualified healthcare provider. Never disregard professional medical advice or delay in seeking it because of something you have heard on this podcast.