How is iron absorbed in humans?

1 Answer
Dec 22, 2017


Here's what I find.


Of our total iron intake,

  • About 10 % to 15 % comes from meat, fish, and poultry as heme
  • About 85 % to 90% comes from grains and vegetables as non-heme iron

Absorption of heme iron

Most of the iron from digested food is absorbed through the duodenal villi.

Heme iron is moved across the cell membrane into the cytoplasm by facilitated transport through heme transporters.

(From SlideShare)

Proteolytic enzymes in the cytosol release the #"Fe"^"2+"# ions, which enter a common pool with non-heme iron.

Absorption of non-heme iron

To be absorbed, non-heme iron must be in the #"Fe"^"2+"# form. Any iron in the #"Fe"^"3+"# form is first reduced to #"Fe"^"2+"# by a ferric reductase.

Intestinal absorption
(From ResearchGate)

A protein called divalent metal transporter 1 (DMT1) then transports the iron into the cell through the cell membrane.

The cell can then either

  • store the #"Fe"^"2+"# by complexing it as ferritin or
  • release the #"Fe"^"2+"# into the body via the iron exporter, ferroportin

The enzyme hephaestin helps ferroportin transfer iron across the cell wall.

The #"Fe"^"2+"# ions are again oxidized to #"Fe"^"3+"# and bound to plasma transferrin for transport throughout the body.