Elemental iron
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Elemental Iron: Bioavailability, Efficacy, and Applications
Introduction to Elemental Iron
Elemental iron is commonly used in food fortification and supplementation to combat iron deficiency. However, its bioavailability and efficacy can vary significantly depending on the form and method of administration. This article synthesizes recent research on the bioavailability, efficacy, and potential applications of elemental iron.
Bioavailability of Elemental Iron Powders
Comparative Bioavailability Studies
Research indicates that elemental iron powders are generally less well absorbed compared to ferrous sulfate (FeSO4). A study evaluating seven different elemental iron powders found that all were significantly less absorbed than FeSO4, with relative bioavailability values (RBVs) ranging from 0.36 to 0.651. Another study confirmed that the bioavailability of iron powders is less than bakery-grade ferrous sulfate, with significant variability among different commercial forms7. The solubility and surface area of iron powders were predictive of their bioavailability in rats7.
Enhancing Bioavailability with Ascorbic Acid
The addition of ascorbic acid (AA) can enhance the bioavailability of elemental iron. For instance, electrolytic iron given with 50 mg of AA was absorbed as well as FeSO4, suggesting that co-fortification with AA could be a viable strategy to improve iron absorption1.
Efficacy of Elemental Iron in Food Fortification
Fortification in Cereal Products
Elemental iron powders are widely used to fortify cereal products. A study comparing the efficacy of wheat-based snacks fortified with ferrous sulfate, electrolytic iron, or hydrogen-reduced iron found that all three forms significantly improved iron status in Thai women with low iron stores. However, the relative efficacy of electrolytic and hydrogen-reduced iron compared to ferrous sulfate was 77% and 49%, respectively4.
Recommendations for Fortification
Based on current evidence, only electrolytic iron powder is recommended for fortification due to its relatively higher absorption compared to other elemental iron powders. It is suggested to be added at double the amount of iron compared to ferrous sulfate to achieve similar efficacy8.
Iron Supplementation and Health Outcomes
Treatment of Iron Deficiency
Elemental iron is also used in the treatment of iron deficiency. A study comparing two doses of elemental iron (60 mg and 80 mg) in women with latent iron deficiency found that both doses were equally effective in normalizing ferritin levels. However, side effects were reported by a majority of participants, which could affect adherence to supplementation2.
Impact on Mitochondrial DNA and Telomere Length
A study on Cambodian women receiving 60 mg of elemental iron daily for 12 weeks found that iron supplementation altered mitochondrial DNA content but did not affect leukocyte telomere length. This suggests potential risks associated with untargeted iron supplementation, highlighting the need for further research to understand the biological consequences3.
Optimizing Iron Supplementation Strategies
Single vs. Split Doses
In a study involving elite runners at altitude, a single nightly dose of 200 mg elemental iron was found to be more effective in increasing hemoglobin mass compared to a split dose of 2 x 100 mg. However, gastrointestinal discomfort was initially higher in the single-dose group but improved over time5.
Novel Iron Particles
Innovative approaches such as using mesoporous iron particles (MIPs) have shown promise in improving iron bioavailability. In vitro and in vivo studies demonstrated that MIPs had higher iron uptake and were effective in recovering hemoglobin levels in iron-deficient rats without significant toxicity10.
Conclusion
Elemental iron remains a crucial component in addressing iron deficiency through fortification and supplementation. While its bioavailability is generally lower than ferrous sulfate, strategies such as co-fortification with ascorbic acid and the use of electrolytic iron powders can enhance its efficacy. Further research is needed to optimize iron supplementation protocols and explore novel iron formulations to maximize health benefits while minimizing side effects.
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Most relevant research papers on this topic
The relative bioavailability in humans of elemental iron powders for use in food fortification
Ascorbic acid may improve the bioavailability of elemental iron for food fortification, as current commercial iron powders are less well absorbed than ferrous sulfate.
Rigorous JournalComparison of Two Doses of Elemental Iron in the Treatment of Latent Iron Deficiency: Efficacy, Side Effects and Blinding Capabilities
Both 60 and 80 mg of elemental iron effectively normalize ferritin levels in women with latent iron deficiency, with similar side effects and blinding capabilities.
RCT
Very Rigorous JournalDaily Oral Supplementation with 60 mg of Elemental Iron for 12 Weeks Alters Blood Mitochondrial DNA Content, but Not Leukocyte Telomere Length in Cambodian Women
Daily oral iron supplementation for 12 weeks in Cambodian women led to altered mitochondrial homeostasis, but not leukocyte telomere length, but more research is needed to confirm the safety of iron supplementation.
RCT
Large Human TrialVery Rigorous JournalComparison of the efficacy of wheat-based snacks fortified with ferrous sulfate, electrolytic iron, or hydrogen-reduced elemental iron: randomized, double-blind, controlled trial in Thai women.
Fortified wheat-based snacks with ferrous sulfate, electrolytic iron, or hydrogen-reduced iron significantly improved iron status in Thai women with low iron stores.
RCTLarge Human Trial
Highly CitedSingle versus Split Dose of Iron Optimizes Haemoglobin Mass Gains at 2106 m Altitude.
A single nightly 200 mg dose of elemental iron is superior to a split dose for optimizing haemoglobin mass changes at altitude in runners over a 3 week training camp.
RCTVery Rigorous JournalComparative bioavailability of elemental iron powders for repair of iron deficiency anemia in rats. Studies of efficacy and toxicity of carbonyl iron.
Carbonyl iron has the highest bioavailability among elemental iron powders for repairing iron deficiency anemia in rats, suggesting it may be suitable for human diets.
Non-RCT
Animal StudyBioavailability of elemental iron powders to rats is less than bakery-grade ferrous sulfate and predicted by iron solubility and particle surface area.
Bioavailability of iron powders is less than bakery-grade ferrous sulfate and varies among different commercial forms, with solubility at pH 1.0 and particle surface area being predictive factors in rats.
Highly CitedThe usefulness of elemental iron for cereal flour fortification: a SUSTAIN Task Force report. Sharing United States Technology to Aid in the Improvement of Nutrition.
Electrolytic iron powder is recommended as an iron fortificant for cereal flours, but it is only half as well absorbed as ferrous sulfate, and should be added to provide double the amount of iron needed.
Literature ReviewHighly CitedEffects of iron deficiency on attention and learning processes in preschool children: Bandung, Indonesia.
Iron supplementation improves cognitive processes related to visual attention and concept acquisition in preschool children with iron deficiency anemia.
RCTHighly CitedIn Vitro and In Vivo Evaluations of Mesoporous Iron Particles for Iron Bioavailability
Mesoporous iron particles (MIPs) show higher iron uptake and regeneration efficiency compared to commercial iron particles, potentially allowing effective recovery of hemoglobin in iron deficiency anemia without significant toxicity.
In Vitro Study