The Science, Microbes & Health Podcast – Details, episodes & analysis

This episode features Prof. Emad El-Omar MD FRCP from the University of New South Wales in Sydney, Australia, speaking about a recent paper exploring the healthy microbiome concept, as well as the latest research on how the gut microbiome contributes to the pathophysiology of several diseases. Prof. El-Omar talked about research on H. pylori-induced disease in the stomach; it’s known that these bacteria decrease acid secretion, which shifts the gastric microbiology in a way that drives progression to cancer. Prof. El-Omar recently co-authored a review paper in Gut that addressed the definition of a healthy gut microbiome. Although a definition has not yet been established, progress is being made by studying healthy people such as centenarians around the world. The best approach may be to define a core microbiome signature that’s present across healthy phenotypes. The core is likely defined by the gut microbiome’s function, so diverse compositions may be able to support health. The paper authors emphasize that pursuing knowledge about what makes a healthy microbiome is a worthwhile pursuit, and they outline what research is necessary to make continued progress in this area. Validation and reproducibility are critical for moving toward clinical applications.

Episode abbreviations and links:

• Review article on the healthy microbiome concept, co-authored by Prof. El-Omar: What defines a healthy gut microbiome?

About Prof. Emad El-Omar MD FRCP:

Professor El-Omar graduated in Medicine from Glasgow University, Scotland, and trained as a gastroenterologist. He worked as a Visiting Scholar/Scientist at Vanderbilt University, TN, and National Cancer Institute, MD, USA, and was Professor of Gastroenterology at Aberdeen University, Scotland, for 16 years before taking up the Chair of Medicine at St George & Sutherland Clinical School, University of New South Wales, Sydney, Australia. He is the Editor in Chief of the journal Gut. His research interests include all aspects of the microbiome, inflammation driven GI cancer and IBD. He is the Director of the Microbiome Research Centre at UNSW/St George Hospital, Sydney.

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This episode features computational microbiologist Dr. Tarini Ghosh PhD from  Indraprastha Institute of Information Technology (Delhi, India) speaking about his recently published paper that proposes a novel Health-Associated Core Keystone (HACK) index for measuring a healthy microbiome. To create the index, the group used a huge volume of sequence data – over 201 terabytes – from more than 45,000 individuals with and without disease across different geographies. The ultimate aim is to create a universal measure for a health-associated microbiome. The HACK index is based on taxa in the gut microbiome, and consists of 3 components:  (1) prevalence and connectedness in the gut microbiome of healthy individuals, (2) longitudinal stability, and (3) association with disease. Keystone taxa were generally more prevalent / abundant in the gut microbiome but not always. The group is now working to connect the identified taxa to specific functions. In the future, this index may be used as a diagnostic tool, possibly to predict a positive response in clinical trials.

Episode abbreviations and links:

• Paper outlining the HACK index: Toward a health-associated core keystone index for the human gut microbiome.
• Review on defining normal microbiome references for global populations: Normal Gut Microbiomes in Diverse Populations: Clinical Implications

About Dr. Tarini Ghosh PhD:

Dr. Tarini Shankar Ghosh leads the Microbiome Informatics group at the Department of Computational Biology at the Indraprastha Institute of Information Technology – Delhi, India. His research focuses on mining global microbiome datasets using advanced statistical methods, machine learning, and deep learning to develop predictive models and indexes that can  facilitate formulation of novel microbiome-derived clinical end-points along with the development of generic and population-specific microbiome-derived diagnostics/therapeutics. His research includes identifying the global and cohort-specific markers of microbiome-resilience and disease, investigating the microbiome taxa associated with response to different therapies and cross-body-site microbiome associations.

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This episode features Dr. Céline Druart PhD of Pharmabiotic Research Institute (PRI) speaking about the role of regulatory science in the development of microbiome biomarkers. First, PRI’s Communication and Membership Manager Camille Bello briefly describes the work of the PRI in supporting the development of therapeutic and diagnostic products derived from microbiome science. Regulation is important to protect consumers and reward innovation, and the development of biomarkers that predict response to treatment, for example, can help move toward personalized medicine. Dr. Druart notes many potential microbiome-based biomarkers have emerged but none have been successfully validated to date. Regulation always follows innovation, and regulatory science is important because it helps regulatory frameworks evolve. A recent Delphi consensus paper co-authored by Dr. Druart acknowledges that biomarker development is a complex process and that a particular challenge is the lack of validation of analytical methods for measuring the microbiome. However, it’s important to remember that techniques can continue to improve even after they’ve been validated. Dr. Druart argues that biomarker validation needs public-private collaborations to design and execute the large clinical studies that are necessary.

Episode abbreviations and links:

• Recent paper co-authored by Dr. Druart: State of the art and the future of microbiome-based biomarkers: a multidisciplinary Delphi consensus
• PRI website: https://pharmabiotic.org/
• PRI LinkedIn page: https://www.linkedin.com/company/pharmabiotic-research-institute-pri
• PRI conference, February 3–5, 2026: https://www.pharmabioticsevent.com/

About Dr. Céline Druart PhD:

Céline Druart obtained her PhD in Biomedical and Pharmaceutical Sciences from UCLouvain (Belgium) in 2014. Following a 3-year project in Patrice Cani’s research group focused on developing the potential beneficial effects of a human gut commensal Akkermansia muciniphila, she worked for 3 years at A-Mansia Biotech (now known as The Akkermansia Company), responsible for clinical programs, regulatory affairs and IP dossiers, as the Scientific and Business Project Manager. Céline joined the PRI in July 2021 as Microbiome Project Manager, managing the Regulatory Science activities of the Association, coordinating Task Group work, and supporting PRI Industry Members in their development planning. She became the PRI’s Executive Director in January 2024.

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This episode features Raphaela Joos from University College Cork in Ireland, speaking about efforts by the Human Microbiome Action Consortium to create an expert-led consensus around the concept of a healthy human microbiome. Ms. Joos, a PhD student who was first author of the resulting paper, notes that a healthy human microbiome can be defined at many different levels. Some parameters such as diversity and resilience are good for a microbial community, and other parameters such as antimicrobial resistance are good for the microbial community but not necessarily good for the host. Another challenge with the definition was how to define health. The group decided that the definition of healthy microbiome needed to be more inclusive than just the microbiome of a healthy person with no disease diagnoses. At present, causality is not clear so we don’t know whether disease-associated microbiomes are adaptive or are driving the disease. The main consensus that emerged from this expert discussion was that more data are needed, tracking large cohorts of people over time in many geographical areas. Only in this way will it be possible to overcome individual variability and truly identify the robust features of a healthy microbiome. Different microbiome compositions can have similar functional capacities, so possibly a functional signature will emerge.

Episode abbreviations and links:

• Perspective paper by Human Microbiome Action Consortium, first authored by Joos: Examining the healthy human microbiome concept

About Raphaela Joos:

Born and bred in Germany, I obtained my BSc in Psychology with a focus on biological neuropsychology, nutrition and statistics at Leiden University and the University of Melbourne. Fascinated by nutritional science and its impact on mental health, I then pursued a MSc on the topic of Microbiome in Health and Disease at King’s College London, delving into microbiology, bioinformatics and microbiome science. After the masters I moved to Cork for a research assistant position investigating the structure and infection mechanisms of bacteriophages involved in cheese fermentation using the protein-folding software AlphaFold. Before starting my PhD, I worked as a project manager under Prof Paul Ross and Prof Aonghus Lavelle on the Human Microbiome Project, organising a workshop featuring international leaders in microbiome research to establish a roadmap to define a healthy microbiome. My PhD now focuses on investigating the role of the infant microbiome in development, applying statistical modelling strategies to integrate functional microbiome data with clinical data.

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This episode features Dr. Gianluca Ianiro MD PhD, a gastroenterologist from the Fondazione A. Gemelli IRCCS and Università Cattolica del Sacro Cuore in Rome (Italy), speaking about how to advance gut microbiome testing for use in medicine. His interest in the gut microbiome began with the clinical observation that fecal microbiota transplantation (FMT) was remarkably successful at curing recurrent C. difficile infection – and from there, he began a program of research on FMT. Current gut microbiome tests are widely variable and don’t provide any clinically relevant information, but some people do them out of curiosity. Over the years it’s become increasingly clear that gut microbiome testing must be standardized to move toward clinical utility. Dr. Ianiro co-authored a recent consensus paper on the challenges of gut microbiome testing and how to move toward standardization. He describes several initiatives that aim to standardize and validate gut microbiome testing, from sample collection to analysis. Dr. Ianiro says promising data exist for gut microbiome testing to predict colorectal cancer, to predict the response to some cancer treatments, and to diagnose inflammatory bowel disease. The field is moving toward some important factors that define a microbiome as “healthy”, but these need to be associated with a clear health outcome if they’re eventually to be used in clinical practice.

Episode abbreviations and links:

• Consensus paper on microbiome testing, co-authored by Dr. Ianiro: International consensus statement on microbiome testing in clinical practice
• “Healthy microbiome” consensus paper by Human Microbiome Action: Examining the healthy human microbiome concept
• Article by Liping Zhao on microbial guild-based analysis of the gut microbiome: Guild-based analysis for understanding gut microbiome in human health and diseases
• Paper from Zitvogel lab on gut microbiome to predict cancer treatment response: Gut microbiome influences efficacy of PD-1–based immunotherapy against epithelial tumors
• Two papers on gut microbiome testing for identifying colorectal cancer: Metagenomic analysis of colorectal cancer datasets identifies cross-cohort microbial diagnostic signatures and a link with choline degradation, Association of distinct microbial signatures with premalignant colorectal adenomas
• Paper on gut microbiome testing for identifying inflammatory bowel disease: Noninvasive, microbiome-based diagnosis of inflammatory bowel disease

About Dr. Gianluca Ianiro MD PhD:

Gianluca Ianiro is a gastroenterologist at the Digestive Disease Center of the Fondazione A. Gemelli IRCCS and adjunct professor in gastroenterology at the Università Cattolica del Sacro Cuore in Rome, Italy.

He has since gone on to establish himself as a key clinical and translational investigator focusing mainly in the field of intestinal microbiota, and has received several research grants in support of his innovative research. His current research is focused mainly on disentangling the rules of donor microbiome engraftment, on investigating microbiome diagnostics and therapeutics in noncommunicable disorders (including cancer), and on bringing microbiome into clinical practice.

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In this episode, the ISAPP hosts discuss human milk and the infant gut with Dr. Simone Renwick PhD from Mother-Milk-Infant Center of Research Excellence (MOMI CORE) at UC San Diego, USA. Dr. Renwick talks about her work investigating how communities of microbes versus individual microbes in the infant gut metabolize human milk oligosaccharide (HMO) structures, and what we know about the origin and functions of the microbes contained in human milk.

Key topics from this episode:

• Dr. Renwick studies how components of human milk foster the development of the infant gut microbiota. These components include HMOs (special sugars found in human milk) and the milk microbiota.
• HMOs cannot be metabolized by the human body, but when microbes in the infant gut break them down, it has health benefits for the infant (because infants who receive no human milk are predisposed to a range of diseases).
• Dr. Renwick used in vitro models to mimic infant microbiota communities, and found that these communities rapidly degraded the HMOs. This metabolism increased microbes associated with health and suppressed potentially pathogenic microbes. 
• Although most research on HMOs focuses on bifidobacteria that are specially equipped to break them down, she looked at individual strains within the infant gut community and found approximately 100 species capable of directly degrading HMOs.
• Once breastfeeding ceases, some microbes in the infant gut adapt to different sources of sugars, but others greatly decrease in abundance.
• Microbes act differently in a community than on their own. Within a complex community, microbes that are better equipped to degrade the HMOs will act quickly, producing byproducts that are then are available to other members.
• All of the different in vitro models have their advantages and disadvantages. The spatial relationships of the human body are often missing in in vitro models.
• Humans appear to have the highest concentration of milk oligosaccharides of any mammal.
• The milk microbiota is another active area of investigation. Live microbes are present in the mammary gland, but their source is still unknown. They tend to resemble the composition of the microbiota on the skin as well as the infant oral cavity, but curiously, anaerobic bacteria are also found in the milk microbiota. Somehow these microbes may move from the mother’s gut to the milk. These microbes may not directly metabolize HMOs. (See this paper.)
• Formula companies are beginning to put HMO structures into their products – mainly 2′-Fucosyllactose.

Episode links:

• Human milk oligosaccharides — Prebiotics in a class of their own? ISAPP webinar.
• The many functions of human milk oligosaccharides: A Q&A with Prof. Ardythe Morrow. ISAPP blog.
• Bifidobacteria in the infant gut use human milk oligosaccharides: how does this lead to health benefits? ISAPP blog.

About Dr. Simone Renwick PhD:

Dr. Simone Renwick is the Milk & Microbes postdoctoral fellow at the Mother-Milk-Infant Center of Research Excellence (MOMI CORE) at the University of California, San Diego, USA. Her research focuses on understanding the role of human milk components, such as the human milk oligosaccharides (HMOs) and milk microbiota, in fostering the developing infant gut microbiota. She is also interested in the potential therapeutic applications of milk components in diseases that affect adults. Currently, Simone is supervised by Drs. Lars Bode, Rob Knight, Pieter Dorrestein, and Jack Gilbert. Prior to her postdoc, Simone completed her PhD in Molecular and Cellular Biology (MCB) at the University of Guelph, Canada, under the supervision of Dr. Emma Allen-Vercoe.

She was the recipient of the Students and Fellows Association poster prize at the ISAPP 2023 meeting in Sitges, Spain.

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This episode features Dr. Anissa Armet PhD RD from the University of Alberta in Canada, speaking about the impact of diet on both the gut microbiota and overall health. Dr. Armet, a registered dietitian and researcher, says the Western diet along with the associated gut microbiome changes have played a role (amongst other things) in the rise of autoimmune diseases in industrialized societies. Dr. Armet describes a recent dietary study she and her collaborators published, for which they created a very high fiber diet called the Non-Industrialized Microbiome restore (NiMe, pronounced “nee mee”) diet. They created recipes and meal plans based on what some non-industrialized populations in the world typically consume, which included 45 grams of dietary fiber per day, and only small portions of animal proteins and dairy products. The participants in this controlled feeding trial saw substantial cardiometabolic benefits as well as certain changes in the gut microbiota after three weeks on the diet. Interestingly, the diet initially reduced the diversity of participants’ gut microbiota, likely because of increased pH in the gut, but diversity rebounded toward the end of the trial. The researchers also introduced a strain of L. reuteri isolated from the gut microbiota of people in a non-industrialized society, to observe whether it would engraft since the diet was known to contain growth substrates for the bacteria. Although the strain did not engraft in the gut microbiota (except in one participant), the health benefits of the diet overall were still observed. The researchers concluded that the NiMe diet can be used to target the gut microbiome and change community characteristics that are relevant for health.

Episode abbreviations and links:

• Dr. Armet’s Instagram account
• Published study on the NiMe diet (called the “restore diet” in the publication): Cardiometabolic benefits of a non-industrialized-type diet are linked to gut microbiome modulation
• Previous research in Papua New Guinea, which informed the NiMe diet: The Gut Microbiota of Rural Papua New Guineans: Composition, Diversity Patterns, and Ecological Processes
• Review on how the gut microbiome informs knowledge about healthy dietary patterns: Rethinking healthy eating in light of the gut microbiome
• New publication from another research group, which complements the NiMe study findings: Immune and metabolic effects of African heritage diets versus Western diets in men: a randomized controlled trial
• Downloadable NiMe diet book: The NiMe Diet: Scientific Principles and Recipes

About Dr. Anissa Armet PhD RD:

Dr. Anissa Armet is a Registered Dietitian and postdoctoral researcher at the University of Alberta. Anissa completed her PhD in Nutrition and Metabolism in March 2024, then transitioned into her postdoc to research the effects of microbiome-targeted dietary interventions in inflammatory bowel diseases. She uses machine learning to determine if the gut microbiome predicts clinical responses in the context of precision nutrition. Anissa has authored several peer-reviewed publications, including a review on healthy eating in light of the gut microbiome and a dietary intervention trial on microbiome restoration. Being equally passionate about knowledge translation, Anissa co-authored an award-winning, open-access, high-protein cookbook designed to support muscle health, is currently developing a plant-based version, and recently co-authored an open-access ebook, The NiMe Diet: Scientific Principles and Recipes.

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This episode features Prof. Yves Desjardins PhD from Laval University in Canada. Prof. Desjardins, an agrologist by training, explains that polyphenols are metabolites synthesized by plants and present in the plant foods we consume. When humans consume polyphenols, we absorb a small fraction (around 5%) of them in the upper gastrointestinal tract, but most of them reach the colon and interact in various ways with the gut microbiota. They have two main effects in the gut, which appear somewhat contradictory: antibacterial effects and a prebiotic-like effect. In the latter case, polyphenols interact with the host epithelium to induce mucin production, creating a niche for certain bacteria to grow. Typical bacteria that increase under these circumstances are bifidobacteria and Akkermansia muciniphila. In these ways, polyphenols have an impact on certain microorganisms and on the microbiome as a whole. In the future, supplements with polyphenols and fiber may be designed to help manipulate the microbiome in a certain way. Currently there are many health benefits associated with polyphenols. The primary benefit is for cardiometabolic health, and some studies also show benefits for cognition.

Episode abbreviations and links:

• Paper proposing the term duplibiotic: Polyphenol-Mediated Gut Microbiota Modulation: Toward Prebiotics and Further
• COSMOS trial on cocoa polyphenols for preventing cardiovascular events and mortality: Effect of cocoa flavanol supplementation for the prevention of cardiovascular disease events: the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized clinical trial
• Study from Desjardins lab on how cranberry polyphenols protect mice against an obesogenic diet: A polyphenol-rich cranberry extract protects from diet-induced obesity, insulin resistance and intestinal inflammation in association with increased Akkermansia spp. population in the gut microbiota of mice
• 2025 paper on how polyphenols are mechanistically connected to metabolic health: Therapeutic Potential of Cranberry Proanthocyanidins in Addressing the Pathophysiology of Metabolic Syndrome: A Scrutiny of Select Mechanisms of Action
• Study on how polyphenols can influence host infections: UPEC Colonic-Virulence and Urovirulence Are Blunted by Proanthocyanidins-Rich Cranberry Extract Microbial Metabolites in a Gut Model and a 3D Tissue-Engineered Urothelium
• Study on how berry polyphenols can improve cognition in people with mild cognitive impairment: Effects of a polyphenol-rich grape and blueberry extract (Memophenol™) on cognitive function in older adults with mild cognitive impairment: A randomized, double-blind, placebo-controlled study

About Prof. Yves Desjardins PhD:

Yves Desjardins is a full professor at the Institute of Nutrition and Functional Foods, Laval University, Québec, Canada. He holds the NSERC/Symrise Partnership Chair on the prebiotic effects of polyphenols (PhenoBio+). Trained in plant physiology, his research focuses on the phytochemistry and functionality of plant bioactives. He has led numerous preclinical and clinical studies on type-2 diabetes, cognitive decline, inflammation, and infections. His current work explores the impact of tannins on gut microbiota, mucosal immunity, and gut barrier function. He has collaborated with the food industry to validate the health benefits of horticultural products (e.g., Urophenol, Glucophenol, Neurophenol). Recognized for his innovative research on fruit polyphenols, he chaired the first International Symposium on Health Effects of Fruits and Vegetables (FAVHEALTH 2005), the OECD Symposium in Lisbon (2010), and organized the 2017 International Congress on Polyphenols and Health in Québec City.

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This episode features Dr. Vanessa Leone PhD from the University of Wisconsin – Madison on how gut microbes and eating patterns impact the host circadian system and overall health. In mouse models, Dr. Leone has found that in a 24-hour period, minor changes occur in the composition of the gut microbiota, while more important changes occur in gut microbiota function (that is, metabolite production). However, these changes depend on the type of diet and the timing of meal consumption. Metabolic health is also affected by this interplay. In humans, obesity is correlated with loss of microbiota rhythmicity, although causality remains unclear. One study by Dirk Haller found that a loss of rhythmicity helped predict which people with prediabetes would progress to diabetes. Constantly shifting timezones (or shifting between day and night shifts) appears to be more detrimental to metabolic health than maintaining a constant schedule, and research is ongoing about what might mitigate these effects. In this field of research it’s important to consider people’s chronotype: their tendency to rise early versus stay up late. In the future, Dr. Leone hopes to untangle more about how different factors affect metabolic health: diet, gut microbiota, and the circadian system.

Episode abbreviations and links:

• Paper from the lab of Dirk Haller showing that 13 OTUs lost rhythms in those with prediabetes, predicting who might develop diabetes: Arrhythmic Gut Microbiome Signatures Predict Risk of Type 2 Diabetes
• Review paper: Daily Eating Patterns and Their Impact on Health and Disease
• Paper on the importance of timing in microbiome sample collection: Time of sample collection is critical for the replicability of microbiome analyses
• University of Wisconsin – Madison Leone Lab webpage

About Dr. Vanessa Leone PhD:

Vanessa A. Leone, Ph.D. is an Assistant Professor in the Department of Animal & Dairy Sciences at the University of Wisconsin-Madison, where she also obtained a Ph.D. She performed postdoctoral studies and was an Instructor of Medicine at the University of Chicago in the Section of Gastroenterology, Hepatology, & Nutrition where she examined how the gut microbiome impacts complex metabolic  diseases. Dr. Leone currently studies how day vs. night oscillatory patterns of gut microbes influence the body’s internal clock and metabolism. She hopes to mechanistically define what constitutes a microbial oscillator versus a non-oscillator, examine how host factors impact the broader diurnal structure and functional outputs of the gut microbiome, and to determine how microbial oscillations impact host metabolism. These findings will likely pave the way to identify how timed delivery of pre-, pro-, or postbiotics can be leveraged to promote a balanced gut microbiota and improve host health.

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This episode features Prof. William Chen from Nanyang Technological University in Singapore, speaking with the ISAPP hosts about precision fermentation. In Singapore, enhancing national food security is of interest and one of the technologies used to achieve this is precision fermentation. Prof. Chen describes the differences between traditional fermentation, biomass fermentation, and precision fermentation. In precision fermentation, food scientists use genetically modified microorganisms to produce a food ingredient of interest. In some cases the product is secreted out of the cell, and in other cases it must be extracted from the cell. The approach has great potential to bypass the need for a large amount of land to produce food, and may reduce costs associated with food production. As this approach continues to develop, education and transparency with consumers is key. Regulatory frameworks and approval processes differ from country to country, and this is an area that will continue to evolve in the years ahead as more food ingredients or other useful products are generated.

Episode abbreviations and links:

• Review: Precision fermentation to advance fungal food fermentations

About Prof. William Chen PhD:

William Chen is the Michael Fam Endowed Professor and Director of Food Science & Technology Programme at Nanyang Technological University Singapore. He is concurrently Director of Singapore Future Ready Food Safety Hub (FRESH). He is also Director of Singapore Agri-food Innovation Lab.

Professor Chen is active in securing and leading large competitive research grants from major government agencies as well as leading international food companies. His food technology innovations have been extensively attracting global attention. His views on food tech innovations, food safety and food security have been regularly covered by major local and international media outlets. He is also advisor/consultant to overseas universities, Singapore government agencies, food industry, and international organizations (ADB, FAO, WHO among others).