Anemia is a condition where there’s a decrease in the number of healthy red blood cells, or RBCs, in the body.
So, iron deficiency anemia means anemia caused by a deficiency in iron.
Iron deficiency anemia is also the most common type of anemia worldwide.
If we take a close look at our red blood cells, we’ll notice that they’re loaded with millions of copies of the same exact protein called hemoglobin, which binds to oxygen and turns our blood cells into little oxygen transporters, and basically allow us to move oxygen to all the tissues in our body.
If we take an even closer look at those hemoglobin proteins, we’ll find that they’re made of four heme molecules, which have, right in the middle, iron.
This iron molecule is what binds to oxygen, so each hemoglobin molecule can bind four molecules of oxygen.
In addition, iron is also an important part of proteins like myoglobin, which delivers and stores oxygen in muscles; and mitochondrial enzymes like cytochrome oxidase, which help generate ATP.
Normally, when a red blood cell dies, some iron is recycled from it.
But, we also lose about 1 milligram of iron every day - some through the sweat, some in shedded skin cells, and some in shedded cells in the gastrointestinal tract, which get out of the body through feces.
But most of us take in 10-20 mg of dietary iron every day, and absorb about 10% of it, or about 1 or 2 milligrams - so it all evens out at the end of the day!
Now, our diet contains two forms of iron.
The first is heme iron, or iron bound to hemoglobin or myoglobin, which comes from animal products like meat.
Heme iron is in the ferrous, or Fe2+, state.
The other form is non-heme iron, which is free iron molecules in the ferric, or Fe3+, state.
Non-heme iron comes from plant based foods like spinach and beans.
Now, when food is broken down in the stomach, iron is released.
Heme iron is absorbed directly into the duodenal cells, where it is broken down to release Fe2+ molecules.
Non-heme iron, however, needs to be reduced to heme iron first.
So the stomach’s hydrochloric acid activates a group of enzymes in the duodenal cells, collectively called ferri-reductase, which live up to their name by reducing non-heme iron to Fe2+ molecules.
Fe2+ molecules then bind to a protein in the duodenal cells called ferritin, which temporarily stores the iron.