Beyond Taxonomy: Fungal Nutraceutical Supplementation Modifies the Functional Potential of the Gut Microbiome in Colorectal Cancer.

The gut microbiome is increasingly recognized as an important determinant of host immune regulation, intestinal homeostasis, and recovery after colorectal cancer (CRC) surgery. Although our previous randomized, double-blind, placebo-controlled clinical trial demonstrated that fungal nutraceutical supplementation with Micodigest® was associated with favorable taxonomic and systemic inflammatory changes in patients undergoing CRC surgery with curative intent, the functional consequences of this intervention remain poorly understood. Here, we performed a functional metagenomic analysis of fecal samples collected from patients enrolled in the original clinical trial to investigate whether Micodigest® supplementation was associated with changes in the functional potential of the gut microbiome. A total of 37 patients were analyzed, including 24 receiving Micodigest® and 13 receiving placebo, with paired samples collected before supplementation and after 4-6 weeks of intervention. Shallow shotgun metagenomic sequencing was performed, and microbial functional potential was characterized using KEGG Orthologues (KOs). Differential abundance analysis identified 14 significantly different KOs between groups at baseline and 23 after intervention, with no overlap between the two sets of orthologues. Following supplementation, Micodigest®-treated patients exhibited increased representation of functions related to CRISPR-associated systems, bacteriophage biology, and chitin-derived carbohydrate utilization, together with reduced representation of nutrient acquisition systems, conjugative transfer, sulfur metabolism, and components of the Wood-Ljungdahl pathway. These functional signatures suggest coordinated changes in microbial ecological adaptation, nutrient utilization, genetic exchange, and metabolic activity following fungal nutraceutical supplementation. Integration with previously reported taxonomic and inflammatory findings supports the hypothesis that Micodigest® may promote coordinated remodeling of the gut microbiome and host-microbiota interactions during the perioperative period. Although the present study cannot establish causality or directly infer microbial activity from metagenomic potential, these findings provide novel functional insights into the microbiome response to fungal nutraceutical supplementation in patients with CRC and highlight functional metagenomics as a valuable complement to taxonomic profiling.