Which form of dietary iron is absorbed more efficiently?

• A. Heme iron from animal sources
• B. Non-heme iron from plant sources
• C. Ferric iron
• D. Ferrous iron

Answer: (A)

Iron from foods comes in two main forms with very different absorption patterns. Heme iron, found in animal foods, is absorbed as an intact molecule through a dedicated pathway, so it enters the body efficiently and with relatively consistent uptake. Non-heme iron, which is mostly from plants, has to be released and converted to the ferrous form before it can be absorbed, and its uptake is strongly affected by dietary factors—enhancers like vitamin C boost absorption, while inhibitors such as phytates and polyphenols impede it. Ferric iron (Fe3+) must be reduced to ferrous iron (Fe2+) before absorption, which makes ferric iron less readily absorbed. Although ferrous iron is the form taken up by intestinal cells, the overall efficiency is higher for heme iron. So, the form absorbed most efficiently is heme iron from animal sources.