Final answer:
Iron absorption is a complex process where ferric iron (Fe³⁺) must be reduced to ferrous iron (Fe²⁺) in the stomach and duodenum for proper uptake, with vitamin C and low pH aiding in this conversion. Proteins and peptides can enhance absorption by forming soluble chelates with iron, while certain conditions and surgeries can affect iron uptake. The body regulates iron levels and storage, with iron fortification in food sometimes using metallic iron as an additive.
Step-by-step explanation:
Absorption of Iron in the Human Body
The absorption of iron is a critical process in human biology. Most dietary iron is in the ferric (Fe³⁺) form which is not readily absorbed by the body. In the duodenum and the proximal jejunum, the body utilizes acidic pH, vitamin C, and proteins like cytochrome B to convert Fe³⁺ to the more absorbable ferrous (Fe²⁺) state. Assisted by a protein called transferrin, the ferrous iron is then transported to various cells for use or storage.
In the stomach, the low pH also facilitates the reduction of Fe³⁺ to Fe²⁺, with vitamin C playing a role as a reducing agent. This conversion is crucial for the proper absorption of iron, which is needed for the formation of hemoglobin and other vital functions. Enhancers of iron absorption include the presence of amino acids and peptides which can form chelates with iron, contributing to its solubility and uptake. Certain conditions like pernicious anemia or hypoplastic anemia can increase iron absorption, while surgical procedures that remove parts of the stomach or intestine may impair it.
Furthermore, the body has mechanisms to regulate iron uptake based on its needs, with iron storage taking place in the form of ferritin within mucosal cells. In some cases, iron fortification in foods uses reduced iron (metallic iron) which is converted to Fe²⁺ in the digestive system, despite the logical use of Fe²⁺ salts as additives.