Where does the majority of iron absorption take place in the human body?

Iron absorption primarily occurs in the duodenum, which is the first segment of the small intestine. This area has specialized cells that are particularly adept at taking up iron, especially in its ferrous (Fe2+) form.

The process is facilitated by various factors, including the acidity of the stomach, which helps keep iron in its soluble ferrous state, and the presence of other dietary components that can enhance or inhibit iron absorption. For example, vitamin C is known to enhance the absorption of iron by reducing ferric iron to its ferrous form and forming complex ions that are more readily absorbed.

In contrast, the ileum, although it is a site for the absorption of several nutrients, primarily absorbs vitamin B12 and bile acids, and is not where the majority of iron uptake occurs. The stomach's role in iron absorption is limited to providing an acidic environment necessary for its initial solubilization, but no significant absorption takes place here. The colon mainly absorbs water and electrolytes and does not significantly contribute to iron absorption either.

Thus, the duodenum's unique structural adaptations and favorable conditions for iron absorption make it the primary site for this essential nutrient.