What is false regarding iron absorption?
**Core Concept**
Iron absorption is a complex process regulated by various factors, including dietary iron content, gastric acidity, and the presence of iron-regulatory proteins. The primary site of iron absorption is the duodenum, where iron is reduced from the ferric to ferrous state and transported across the enterocyte membrane.
**Why the Correct Answer is Right**
Iron absorption is influenced by several factors, including the presence of vitamin C, which enhances non-heme iron absorption by reducing ferric iron to the ferrous state. Heme iron, on the other hand, is absorbed independently of vitamin C and is not affected by gastric acidity. The iron-regulatory protein hepcidin plays a crucial role in regulating iron absorption by binding to the iron exporter ferroportin and inducing its internalization and degradation.
**Why Each Wrong Option is Incorrect**
**Option A:** Iron absorption is increased in the presence of vitamin C. This statement is true, as vitamin C enhances non-heme iron absorption by reducing ferric iron to the ferrous state.
**Option B:** Heme iron is absorbed in the jejunum. This statement is false, as heme iron is absorbed in the duodenum, where it is taken up by the heme transporter.
**Option C:** Hepcidin regulates iron storage, not absorption. This statement is false, as hepcidin regulates iron absorption by binding to ferroportin and inducing its internalization and degradation.
**Clinical Pearl / High-Yield Fact**
It's essential to note that excessive iron absorption can lead to iron overload, a condition characterized by the accumulation of iron in various tissues, including the liver, heart, and pancreas.
**Correct Answer:** B. Heme iron is absorbed in the duodenum.