Researchers constructed a comprehensive knowledge graph connecting dietary exposures to health outcomes through gut microbiome mechanisms, analyzing 1,309 studies to identify 4,772 weighted pathways. The system achieved 100% coverage of established metabolic pathways including butanoate metabolism and secondary bile acid biosynthesis, with 92% accuracy across five validated biological pathways. Key mechanisms emerged including the probiotic-short chain fatty acid-immunity axis supported by 34 studies, and the high-fat diet-lipopolysaccharide-endotoxemia cascade documented in 8 studies. This represents a significant methodological advance in nutritional science by systematically organizing fragmented evidence into a unified, AI-readable framework. The implications extend beyond academic research into practical health optimization, particularly for aging adults seeking evidence-based dietary interventions. The knowledge graph's ability to preserve relationship polarity and biological direction addresses a critical gap in translating microbiome research into actionable health guidance. However, the reliance on published abstracts may introduce publication bias, and the 2023-2025 timeframe, while recent, represents a narrow temporal window. This work establishes a scalable foundation for personalized nutrition recommendations and could accelerate the development of targeted interventions for immune regulation, muscle health, and metabolic aging.