Nano-enabled strategies for iron deficiency and iron deficiency anemia: iron-based nanoparticles for supplementation, bioavailability, and food fortification-a narrative review.

Iron deficiency and iron deficiency anemia (IDA) remain highly prevalent worldwide and are associated with substantial morbidity, especially among infants, children, women of reproductive age, and individuals with chronic diseases. Conventional oral iron salts and food fortification strategies are often limited by gastrointestinal side effects, poor adherence, and unfavorable sensory changes in fortified foods. Nano-enabled iron formulations have been proposed to overcome these limitations by improving bioavailability while preserving tolerability and product quality. This narrative review summarizes in vitro, in vivo and human studies on iron oxide, iron oxyhydroxide, ferric phosphate, ferric pyrophosphate and ferrous sulfate nanoparticles used for oral supplementation or food fortification in the context of iron deficiency and IDA. Overall, nano-sized iron sources tend to show improved iron bioaccessibility and relative bioavailability than their bulk or conventional counterparts, particularly for poorly soluble compounds, and several preparations appear to reduce gastrointestinal intolerance and sensory changes in foods. Early human data suggest that selected nano-iron formulations can approach the hematological efficacy of ferrous sulfate while offering technological advantages for incorporation into complex food matrices. However, most evidence still derives from short-term or preclinical studies, and important gaps remain regarding long-term safety, organ-specific accumulation, effects on the gut microbiota and performance in diverse at-risk populations. Future work should prioritize well-designed clinical trials, standardized physicochemical and toxicological characterization, and clear regulatory guidance to support the safe and effective integration of nano-enabled iron formulations into nutritional strategies against iron deficiency.