Iron and calcium are absorbed primarily in which part of the small intestine?

• A. Jejunum
• B. Duodenum
• C. Ileum
• D. Colon

Answer: (B)

The duodenum is the primary site where both iron and calcium absorption occur. Iron absorption is most active here due to specialized transporters in enterocytes (such as DMT1 for uptake and ferroportin for export) and the favorable, acidic milieu that helps iron solubility. Calcium absorption also occurs mainly in the duodenum (with contribution from the proximal jejunum) and is regulated by vitamin D, which increases the expression of calcium transport proteins like TRPV6 and calbindin. Because this region houses the key mechanisms for both minerals, it’s the best answer. The ileum and colon are not the primary sites for iron or calcium absorption, and the jejunum, while important for many nutrients, is not the main site for these two minerals.