From the Guidelines
Iron is primarily absorbed in the duodenum, which is the first part of the small intestine. The absorption process begins immediately after the stomach, where the acidic gastric environment helps convert dietary iron to its ferrous (Fe2+) form, making it more readily absorbable. The duodenum contains specialized cells with microvilli that increase the surface area for absorption, and these cells express specific iron transport proteins like DMT1 (divalent metal transporter 1) that facilitate iron uptake. While some minimal iron absorption can occur in other parts of the small intestine like the jejunum, the duodenum remains the principal site for iron absorption, as supported by studies such as 1 and 1, which highlight the importance of the duodenum in iron absorption due to its acidic environment and the presence of specific iron transport proteins. This localization is physiologically important because iron needs the acidic environment from the stomach to remain soluble, and the duodenum's proximity to the stomach ensures optimal conditions for absorption before the intestinal contents become more alkaline further down the digestive tract. Key factors influencing iron absorption include the conversion of dietary iron to its ferrous form, the role of duodenal cytochrome B in solubilizing iron, and the function of DMT1 in transporting iron into the mucosal cell, as described in 1. Overall, the duodenum's unique environment and specialized cells make it the primary site for iron absorption in the gastrointestinal tract.
From the Research
Iron Absorption in the Gastrointestinal Tract
- Iron (Fe) is primarily absorbed in the duodenum [ 2, 3,4 ]
Locations of Iron Absorption
- The duodenum is the first part of the small intestine and is responsible for most of the iron absorption 4
- The expression of molecules involved in iron absorption, such as DMT1, ferroportin, and Zip8, varies along the length of the duodenum [ 2 ]
- Duodenal macrophages play a role in regulating iron absorption by controlling the degradation of transferrin 3
Regulation of Iron Absorption
- Iron absorption is regulated according to the body's needs, increasing in iron deficiency and decreasing in iron overload 4, 5
- The liver plays a major role in systemic iron regulation, producing the iron regulatory hormone hepcidin 5
- Hepcidin is a negative regulator of iron absorption and recycling, binding to ferroportin and causing its internalization and degradation 5