What blocks iron absorption
Pro Research Analysisby 
Searched over 200M research papers
Factors Blocking Iron Absorption
Iron absorption is a complex process regulated by various mechanisms within the body. Several factors can inhibit the absorption of iron, leading to conditions such as iron deficiency anemia. This article explores the primary mechanisms and factors that block iron absorption, drawing insights from recent research.
Mucosal Block Mechanism
Role of Iron Regulatory Proteins (IRPs)
Iron regulatory proteins (IRPs) play a crucial role in controlling iron absorption at the cellular level. IRP deficiency can impair iron absorption and promote mucosal iron retention through a ferritin-mediated "mucosal block" . This block prevents excessive iron from entering the bloodstream by retaining it within the mucosal cells.
Impact of Oral Iron Doses
A phenomenon known as the mucosal block occurs when a large oral dose of iron reduces the absorption of a subsequent smaller dose. This is due to a rapid decrease in the expression of brush border iron transport molecules such as divalent metal transporter 1 (DMT1) and Dcytb, while basolateral transport molecules like Ireg1 and hephaestin remain unaffected . This indicates that the mucosal block is primarily regulated by local enterocyte iron levels.
Historical Perspective on Mucosal Block
The concept of the mucosal block was first proposed by Hahn et al., who demonstrated that an initial dose of iron could diminish the absorption of a subsequent dose . This refractory state of the intestine can last up to 24 hours, highlighting the body's ability to regulate iron absorption based on recent iron intake.
Iron Chelation and Parenteral Agents
Desferrioxamine (DFO)
Desferrioxamine (DFO) is an iron chelating agent that can block iron absorption when administered parenterally. Studies have shown that DFO can significantly reduce the absorption of various forms of iron, including inorganic iron, transferrin iron, and hemoglobin iron, by binding intracellular iron within the intestinal mucosa . This suggests that DFO can enter the small intestinal mucosa and interfere with iron absorption pathways.
Regulatory Mechanisms
Hepcidin and Systemic Regulation
Hepcidin, a hormone produced by the liver, plays a central role in regulating iron absorption. High levels of hepcidin decrease circulating iron by inhibiting its recycling from macrophages and its absorption in the intestine . This systemic regulation ensures that iron levels remain balanced, preventing both deficiency and overload.
Iron Responsive Element (IRE)/Iron Regulatory Protein (IRP) System
The IRE/IRP system is another critical regulatory mechanism that controls the expression of iron uptake and storage proteins. This system helps regulate iron absorption by adjusting the levels of proteins involved in iron transport based on the body's iron needs .
Dietary Influences
Diet Composition
Dietary factors can also influence iron absorption. For instance, a diet high in certain grains, such as corn grits, can lead to increased iron absorption and subsequent iron overload in the liver . This suggests that dietary composition can override the normal regulatory mechanisms, leading to excessive iron absorption under certain conditions.
Conclusion
Iron absorption is tightly regulated by a combination of local and systemic mechanisms. The mucosal block, influenced by IRPs and local iron levels, plays a significant role in preventing excessive iron absorption. Additionally, systemic factors like hepcidin and the IRE/IRP system ensure that iron levels remain balanced. Understanding these mechanisms is crucial for developing strategies to manage iron-related disorders effectively.
Sources and full results
Most relevant research papers on this topic