CDDW- Canadian DDW

While most microbiome research has focused on bacteria, the gut mycobiome—comprising fungal communities such as Candida, Saccharomyces, and Malassezia—is increasingly recognised as an important contributor to intestinal health and disease. In inflammatory bowel disease (IBD), alterations in fungal composition have been linked to immune activation and mucosal inflammation. Certain fungi can interact with host immune receptors, triggering pro-inflammatory pathways and influencing intestinal barrier integrity. Genetic susceptibility factors in IBD may also alter host responses to fungal antigens. Understanding the mycobiome expands the concept of dysbiosis beyond bacteria and highlights new potential therapeutic targets aimed at modulating fungal–immune interactions in intestinal inflammation.

• Shift away from pro-inflammatory T cells: They dampen Th1/Th17-type responses and reduce inflammatory cytokine signalling.

• Boost regulatory networks: They expand regulatory T cells (Tregs) and increase anti-inflammatory mediators (often including IL-10 and TGF-β–linked pathways).

• Promote type-2 immunity and repair: Helminths induce Th2-biased responses and stimulate epithelial repair mechanisms (mucus production, goblet cell activity, barrier reinforcement).

• Reprogram innate immunity: They polarise macrophages toward an M2/regulatory phenotype, temper dendritic cell activation, and can stabilise mast cell/innate signalling.

• Microbiome and metabolite effects: Helminths can indirectly modify bacterial communities and metabolites, potentially reducing dysbiosis-driven inflammation.

Evidence and clinical potential (where we stand)

• Human trials of live helminths (notably Trichuris suis ova and Necator americanus) have shown mixed and often disappointing efficacy, with variable colonization, dosing challenges, and inconsistent endpoints. Benefit, when seen, appears limited to subsets and is not reliably reproducible.

• Safety/tolerability: Generally acceptable in controlled studies, but real-world scalability raises concerns: symptom burden, anemia/nutrient effects (species-dependent), immunosuppressed-host risk, and regulatory complexity of administering live organisms.

• Where the field is heading: The most promising path is moving from “worms” to defined helminth-derived molecules (secreted proteins/EVs) or synthetic analogs that deliver immunoregulatory effects without infection, plus better patient stratification (phenotype, microbiome, immune signatures).

Bottom line: Helminths provide a compelling immunology blueprint for IBD immune regulation, but live helminth therapy is unlikely to become mainstream; helminth-inspired biologics and precision targeting are the more realistic future.

Live bacterial therapeutics (LBTs) represent an emerging “living medicine” strategy for colorectal cancer (CRC), designed for both detection and treatment by exploiting the natural ability of certain bacteria to localize within the gut lumen, mucus layer, and tumor-associated niches.

Several therapeutic approaches are under development. Fecal microbiota transplantation (FMT) can broadly modify the gut ecosystem but has limitations due to donor variability and poor reproducibility, making it less suitable for precise CRC detection. Engineered probiotics, based on well-characterized food-grade bacteria, offer improved safety and manufacturing control but may require repeated dosing because of limited long-term colonization. Engineered native bacteria, derived from host-adapted commensals, may achieve better persistence but pose challenges related to personalization and regulatory standardization. Advances in synthetic genetic circuit engineering allow bacteria to sense tumor signals and generate programmed responses, though maintaining genetic stability and safety remains challenging.

For detection, engineered bacteria follow a “tumor cue → bacterial sensor → measurable output” model. Tumor-associated signals such as hypoxia, inflammatory metabolites, or altered nutrient environments can trigger bacterial reporters detectable in stool or urine, enabling non-invasive monitoring.

Therapeutically, bacteria may deliver immunomodulators, cytotoxic proteins, or prodrug-activating enzymes, with controlled release mechanisms such as quorum-sensing circuits. Robust biocontainment strategies, including kill-switch systems and antibiotic-sensitive strains, are essential for safe clinical translation of these innovative therapies.

Early-life intestinal viral infections may play an important role in shaping long-term gut health. During infancy, the immune system and gut microbiome are still developing, making this a critical window for immune education. Certain viruses can influence how the immune system learns to distinguish between harmful pathogens and beneficial microbes. These early interactions may affect susceptibility to gastrointestinal diseases later in life, including inflammatory bowel disease and other immune-mediated conditions. Maternal antibodies and early immune responses also help guide the development of protective immunity. Understanding these early virus–host interactions may help explain lifelong patterns of gut health and disease risk.

The gut–liver axis plays a central role in the development and progression of metabolic dysfunction–associated steatotic liver disease (MASLD). Increasing evidence suggests that the intestinal microbiome acts as a key regulator of hepatic inflammation, metabolic signaling, and disease severity. Because the liver receives nearly 70% of its blood supply from the portal circulation, it is continuously exposed to microbial metabolites, endotoxins, and immune signals originating from the gut.

In MASLD, alterations in gut microbial composition—often referred to as dysbiosis—can promote increased intestinal permeability and enhanced translocation of bacterial products such as lipopolysaccharides and microbial metabolites. These molecules activate hepatic immune pathways, contributing to inflammation, steatohepatitis, and fibrosis progression.

Recent research has focused on developing diagnostic tools that incorporate microbiome-derived biomarkers to better predict disease severity. Metagenomic sequencing, microbial metabolite profiling, and microbiome-based predictive models are being explored as potential non-invasive approaches to distinguish simple steatosis from steatohepatitis and advanced fibrosis.

In addition, specific microbial metabolic pathways—such as those involved in short-chain fatty acid production, bile acid metabolism, and ethanol generation by gut bacteria—have been linked to MASLD progression.

Understanding the microbiome’s influence at the gut–liver interface may ultimately allow clinicians to develop novel diagnostic strategies and targeted therapies, including microbiome modulation through diet, probiotics, or microbiota-directed treatments.

The gut microbiome–host–nutrition axis represents a dynamic system in which diet directly influences microbial composition, metabolic activity, and ultimately gastrointestinal health. This relationship is particularly critical in early life, when the microbiome is still developing and can have long-lasting effects on immune maturation, metabolism, and disease susceptibility.

Dietary components such as fiber, complex carbohydrates, fermented foods, and prebiotic substrates provide nutrients that shape microbial diversity and function. In contrast, highly processed diets and excessive simple sugars can promote dysbiosis, which has been associated with conditions such as inflammatory bowel disease, functional gastrointestinal disorders, obesity, and metabolic liver disease. Early-life exposures—including breastfeeding, complementary feeding practices, and antibiotic exposure—also play a key role in determining long-term microbiome patterns.

Recent research has begun to integrate microbiome sequencing with predictive nutritional models, enabling researchers to better understand how specific foods influence microbial metabolic outputs and host responses. These insights are paving the way for microbiome-informed dietary strategies, where nutrition interventions are designed to selectively promote beneficial microbial pathways.

In clinical practice, practical approaches include increasing dietary fiber, encouraging diverse plant-based foods, promoting fermented foods when appropriate, and limiting ultra-processed foods. Particularly in pediatric populations, these strategies may help guide microbiome development and support long-term gastrointestinal and metabolic health.

The concept of “food as medicine” is gaining increasing recognition as a practical strategy for preventing and managing chronic diseases, particularly those affecting the gastrointestinal system. Dietary patterns play a central role in the development and progression of conditions such as obesity, metabolic dysfunction–associated steatotic liver disease (MASLD), inflammatory bowel disease, and functional gastrointestinal disorders. As a result, modern healthcare is increasingly emphasizing the integration of nutrition directly into clinical care.

Culinary medicine is an emerging interdisciplinary field that combines nutrition science, clinical medicine, and culinary skills to help patients translate dietary recommendations into practical, sustainable eating habits. The field originated from programs developed in academic medical centers, where physicians, dietitians, and chefs collaborate to teach patients and healthcare professionals how to prepare healthy, disease-specific meals.

In pediatric gastroenterology, culinary medicine offers unique opportunities. Early dietary interventions can influence lifelong metabolic health, gut microbiome development, and gastrointestinal function. Practical applications include structured programs for children with obesity, fatty liver disease, celiac disease, and functional GI disorders, where hands-on cooking education can improve adherence to therapeutic diets.

Importantly, culinary medicine shifts the focus from restrictive dieting toward empowering families with practical food skills and culturally appropriate dietary choices. By bringing healthcare into the kitchen, clinicians can bridge the gap between medical advice and everyday eating behaviors, making nutrition a more effective therapeutic tool.

The widespread use of GLP-1–based therapies (e.g., semaglutide, tirzepatide) has transformed obesity management by directly targeting central appetite regulation, satiety pathways, and gastric emptying. These agents significantly reduce energy intake and promote weight loss, but they also challenge traditional nutrition paradigms that focused primarily on calorie restriction and behavioral dietary control.

With GLP-1 therapy, weight loss is driven largely by pharmacologically mediated appetite suppression, meaning patients often experience reduced hunger, early satiety, and lower overall food intake. While this improves weight outcomes, it also raises new nutritional concerns. Reduced caloric intake can lead to loss of lean body mass, inadequate protein intake, and micronutrient deficiencies, particularly if nutritional counseling is not integrated into treatment.

Therefore, modern obesity care in the GLP-1 era must shift from simply “eating less” to strategic nutrition planning that preserves metabolic health and body composition. Key strategies include prioritizing protein intake, maintaining adequate micronutrient consumption, ensuring hydration, and incorporating resistance exercise to preserve muscle mass during weight loss.

Clinicians should also recognize that GLP-1 therapies may alter meal patterns and dietary tolerance, with smaller, more frequent meals often better tolerated than large portions.

Overall, the emerging paradigm emphasizes combining pharmacotherapy with targeted nutritional support. Rather than replacing lifestyle interventions, GLP-1 therapies require more precise nutrition guidance to optimize weight loss, preserve lean mass, and sustain long-term metabolic health.

The gastrointestinal tract is protected by multiple layers of defense. After the epithelial and vascular barriers, the mucosal immune system acts as the second major line of defense, maintaining a delicate balance between tolerance to beneficial microbiota and protection against pathogens.

Unlike systemic immunity, the adaptive mucosal immune system is uniquely tuned to the intestinal environment, where trillions of commensal microbes coexist with the host. Immune responses are therefore triggered only when microbial antigen exposure crosses a high threshold, preventing unnecessary inflammation against harmless microbiota.

A central component of mucosal immunity is the production of secretory IgA antibodies by B cells. These antibodies coat intestinal microbes and limit their interaction with the mucosal surface without causing tissue-damaging inflammation. Interestingly, IgA responses are highly durable and dynamic—rather than fading over time, IgA-producing cells are continually replaced to maintain long-term microbial control.

T cells also play a crucial regulatory role. Memory T cells in the intestinal mucosa can persist and cycle even in the absence of ongoing antigen exposure, ensuring rapid responses if microbial balance is disturbed.

Importantly, mucosal immune responses show features of “semi-innate” behavior. B cells often use conserved VDJ gene sequences with a limited repertoire, while T cells converge on shared effector pathways that allow rapid responses.

Together, this specialized immune system allows the gut to maintain tolerance to beneficial microbes while remaining prepared to defend against potential threats.

The gastrointestinal tract maintains health through two closely linked protective systems: the epithelial barrier and the vascular barrier. While the epithelial barrier—formed by tight junctions between intestinal epithelial cells—prevents luminal microbes and toxins from entering the tissue, the gut vascular barrier (GVB) represents a second critical checkpoint that regulates what passes from the intestinal mucosa into the systemic circulation.

The vascular barrier consists of intestinal endothelial cells, pericytes, basement membrane components, and immune signaling pathways that tightly control vascular permeability. Under normal conditions, this barrier prevents bacteria, endotoxins, and inflammatory molecules from entering the bloodstream while allowing selective transport of nutrients and immune mediators.

Disruption of the gut vascular barrier has been increasingly recognized in several gastrointestinal disorders. In conditions such as inflammatory bowel disease, liver cirrhosis, and metabolic diseases, increased vascular permeability may allow bacterial products and inflammatory mediators to translocate into the portal circulation. This process can contribute to systemic inflammation, liver injury, and disease progression.

Recent research highlights that the epithelial and vascular barriers function as a coordinated defense system. When epithelial integrity is compromised, the vascular barrier acts as a secondary protective filter. However, when both barriers fail, microbial translocation and immune activation can occur.

Understanding the biology of the gut vascular barrier is opening new avenues for therapeutic strategies aimed at restoring intestinal barrier integrity and preventing systemic inflammation in gastrointestinal diseases.