腸内細菌叢と鉄欠乏性貧血：メカニズム、微生物学的特徴、食事との相互作用（総説）

BACKGROUND AND OBJECTIVES: Iron deficiency anemia (IDA) is one of the most prevalent micronutrient disorders worldwide. Recent work suggests that dysbiosis may not simply be a consequence of low iron status but may actively contribute to impaired absorption. This narrative review synthesizes the evidence on gut microbiota patterns in IDA across age groups, examines the mechanistic links between dysbiosis and iron metabolism, and identifies the potential roles of microbiota-related dietary and therapeutic strategies. METHODS AND STUDY DESIGN: This narrative review used a selective, theory-driven approach, based on targeted searches of PubMed, Scopus, and Web of Science (2005-2026), to synthesize heterogeneous human, experimental, and mechanistic evidence on gut microbiota-iron interactions in iron deficiency anemia (IDA). RESULTS: Evidence suggests a bidirectional, context-dependent relationship between IDA and gut microbiota involving host iron regulation, microbial competition, metabolites, and diet. Individuals with IDA often show reduced microbial diversity, depletion of SCFA-producing taxa, and enrichment of iron-scavenging bacteria, although direct causal evidence in humans remains limited. CONCLUSIONS: IDA is commonly associated with recurring dysbiosis patterns characterized by reduced short-chain fatty acid-producing commensals and relative enrichment of inflammatory, iron-competitive taxa. While iron supplementation remains the cornerstone of evidence-based IDA management, the ecological effects of unabsorbed luminal iron on gut microbial communities support the concept of a potential "iron paradox," particularly in inflammatory or high-infection settings. Therefore, microbiota-targeted strategies should currently be regarded as hypothesis-generating concepts rather than established clinical interventions and require further mechanism and clinical validation.