[JunkDNA]

This. I remember my biochemistry professor in college grinding up a bowl of cereal into a fine powder and then using a magnet to yank all the iron out. Fine iron powder like the kind present in cereals is nowhere near as bioavailable as iron complexed with proteins (e.g. from red meat). You basically just poop most of it out. Ask anyone who has had an iron deficiency. It is ferociously difficult to take enough supplements and change your diet enough to correct a severe form of it.