I’ve heard that bread, in particular, is enriched in iron by mixing iron dust or powder into the dough or flour. A bit of a web search suggests that this may at one time have been true. Was it? Is it still the case? How is it done nowadays? What about other foods?
Mr. Wizard did this in the 80’s. He poured a large box of cereal in a mixing bowl with water and stirred it with a magnetic stirrer. After some time, the magnet was covered with iron filings. So as far as I know, the iron in food is actually iron.
I remember that, I’ve seen teachers do it as well. IIRC, they usually use Total cereal. Ever since then, I always just assumed that when food mentions iron, it’s actually the metal we’re all familiar with and when they say it’s fortified with iron that they’re actually adding iron filings to it.
The term I came across in trying to find a good answer for this was “iron powder,” so hopefully it’s ground a little finer than would qualify for the term “filings.”
This is the closest thing I found to an definitive “yes, we just pour iron in the food”:
The superscripts all refer to footnotes in the original PDF.
Cecil has discussed this: http://www.straightdope.com/columns/read/676/do-iron-fortified-cereals-really-contain-iron-filings.
Ferrous sulfate isn’t iron powder; it’s a compound containing iron. Just plain iron will be listed in the ingredients as “reduced iron”.
rust, Fe2O3, i remember one food product saying so.