Biohacking the human gut microbiome for precision health and therapeutic innovation.

Biohacking, the self-directed application of biotechnology, digital tools, and lifestyle interventions, has rapidly converged with gut microbiome science to create adaptive, individualized, and minimally invasive precision-health paradigms. This narrative review integrates current evidence on diet-based modulation, microbial therapeutics (probiotics, prebiotics, postbiotics, and fecal microbiota transplantation), and synthetic-biology approaches (engineered strains and phage or synthetic consortia) within a multi-omics and continuous-phenotyping framework. Mechanistically, short-chain fatty acids (SCFAs), bile-acid derivatives, and tryptophan catabolites operate as endocrine-like mediators linking gut microbial ecology with host immunity, metabolism, and neuroendocrine signaling. Pathways mediated by microbial metabolites underpin translational applications that span metabolic optimization, through improved insulin sensitivity, reduced adiposity, and attenuation of inflammation, and neurocognitive enhancement via the microbiome-gut-brain axis. Evidence from oncology further indicates that microbial metabolites and engineered taxa remodel stromal and immune niches, shaping therapeutic response and disease progression. Concurrently, emerging digital infrastructures, wearables, biosensors, metabolic avatars, and AI-driven "health twins," enable real-time, closed-loop modulation of host-microbe dynamics. Persistent challenges include methodological heterogeneity, safety concerns regarding live biotherapeutics and unsupervised fecal microbiota transplantation (FMT), fragmented regulation, and vulnerabilities in cyberbiosecurity and data equity. We propose a translational roadmap emphasizing standardized metadata (STORMS), validated reference frameworks, longitudinal multi-omics for causal inference, strain-level safety genomics, and governance integrating ethical and cybersecurity oversight. Under these conditions, microbiome-focused biohacking may evolve from anecdotal experimentation into a more reproducible and scientifically grounded component of preventive and personalized medicine. This manuscript is presented as a narrative and conceptual review, integrating validated microbiome research with emerging biohacking frameworks while explicitly distinguishing evidence-based findings from exploratory or speculative concepts.