Iron in the human body
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Iron’s Essential Roles in the Human Body
Iron is a vital trace element required for many key biological processes in humans. It is crucial for oxygen transport, as it forms part of hemoglobin in red blood cells, enabling oxygen delivery from the lungs to tissues and the return of carbon dioxide for exhalation Gupta2014Ems2019Yiannikourides2019+5 MORE. Iron is also necessary for DNA synthesis, energy production in mitochondria, and the function of various enzymes involved in metabolism and cell growth Gupta2014Chouhan2021Ems2019+6 MORE. Additionally, iron supports immune function and is involved in the production of hormones and neurotransmitters Gupta2014Chouhan2021.
Iron Distribution, Storage, and Recycling
About 70% of the body’s iron is found in hemoglobin within red blood cells, while the rest is stored in proteins such as ferritin and hemosiderin, or transported in the blood by transferrin Gupta2014Ems2019Yiannikourides2019+4 MORE. Iron is also present in muscle cells as myoglobin and in various enzymes Ems2019Yiannikourides2019Enko2025+2 MORE. When red blood cells die, their iron is recycled by macrophages in the spleen, liver, and bone marrow, and reused for new red blood cell production Gupta2014Yiannikourides2019Enko2025+3 MORE. The liver acts as a major storage site for iron, mainly in the form of ferritin Svobodova2020Vogt2021.
Iron Absorption and Regulation
Iron is not synthesized by the body and must be obtained from the diet, either as heme iron from animal sources or non-heme iron from plant sources Enko2025Anderson2017Abbaspour2014+2 MORE. Absorption occurs mainly in the duodenum and is tightly regulated, as there is no active mechanism for iron excretion—losses occur passively through sweat, skin, hair, and menstruation Ems2019Yiannikourides2019Enko2025+4 MORE. The hormone hepcidin, produced by the liver, is the master regulator of iron metabolism. It controls iron absorption and release from storage by regulating the iron transporter ferroportin Yiannikourides2019Enko2025Anderson2017+1 MORE. When iron levels are high, hepcidin increases to reduce absorption and release; when iron is low, hepcidin decreases to allow more iron into the bloodstream Yiannikourides2019Enko2025Anderson2017+1 MORE.
Iron Deficiency and Overload
Both iron deficiency and excess can have serious health consequences. Iron deficiency impairs oxygen transport, reduces work and intellectual capacity, affects growth, and weakens the immune system Chouhan2021Yiannikourides2019Anderson2017+1 MORE. Iron overload, often due to genetic disorders or repeated blood transfusions, can cause tissue damage and contribute to diseases such as hemochromatosis and neurodegenerative conditions Svobodova2020Anderson2017Abbaspour2014+1 MORE. Because free iron is toxic, the body uses proteins like ferritin to safely store and regulate iron Svobodova2020Abbaspour2014.
Conclusion
Iron is indispensable for human health, supporting oxygen transport, energy production, and many metabolic processes. Its levels are carefully balanced through absorption, storage, and recycling, primarily regulated by the hormone hepcidin. Both deficiency and overload of iron can lead to significant health problems, highlighting the importance of maintaining proper iron homeostasis in the body Gupta2014Chouhan2021Ems2019+7 MORE.
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