What is manufactured from the iron that we obtain from our diet?

Iron absorbed from the diet is used mainly to make haemoglobin, the iron-containing pigment of red blood cells that carries oxygen. Bone marrow is the tissue where blood cells are made, not a product of iron, and blood cells as a whole and protoplasm are not what dietary iron is built into; a lack of iron shows up as anaemia from low haemoglobin.