eli5: Why do we need iron as a nutrient? I understand iron as a metal. Why do we need to consume it?
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Iron is the stuff that bonds oxygen in hour red blood cells and helps blood carry said oxygen around our body. And it carries carbon dioxide to our lungs where we can exhale it out of our system. Without enough iron that process becomes less effective, which is bad.
Your body uses iron in lots of ways. The most prominent, though, is in your blood. It is a necessary part of hemoglobin, the molecule in your red blood cells that allows them to transport oxygen and CO2.
Your body uses plenty of different metals for various chemical processes.
Iron has that same property on the molecular and on macro level: It reacts good with oxygen, or on a visible scale: It rusts.
An adult body contains 4-6 grams of iron, i think the most of it is in the blood for oxygen transport.
And just like most things, too much of something that we need to live is bad too. Hemochromatosis is the body’s inability to process iron efficiently. “Unused” iron just builds up and floats around, eventually collecting in vital organs and causing problems
Our body uses elements like iron (and other metallic elements such as potassium, sodium, etc) to work. One key use of iron is in blood. Hemoglobin, the part of blood that carries oxygen is iron based. It’s also part of some hormones.
More generally, we have enzymes that speed up chemical transformations, like converting sugar energy to energy used for muscles. These enzymes are proteins, but they sometimes have non-protein components called cofactors. The non-protein components of enzymes often contain iron (also sometimes copper and other metals) because these metals are better than proteins in some chemical transformations such as transferring electrons.
Many people mentioned iron being involved in the oxygen-carrying activity of hemoglobin, which is a good example. A similar iron-containing structure is part of many other proteins, including proteins involved in extracting energy from food, and proteins carrying out photosynthesis. Iron is part of many other, very different, enzymes as well. For example, there are iron-sulfur structures in many enzymes that are unrelated to the iron-containing structure in hemoglobin.
Hemoglobin is the big one- it’s the part of your blood that oxygen combines with, so that it can be given out to your body’s cells.
But WHY iron? It’s a metal that combines and releases oxygen relatively easy compared to other chemicals. There’s oxygen in the sugar in your body, and basically in every part, but it doesn’t get released easily when it’s part of other chemicals. So iron fills in somewhat of a niche role here.
Interestingly enough, for life in general it doesn’t HAVE to be iron. Horseshoe crabs have hemocyanin- a chemical that binds copper to oxygen.
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