Say you eat a bowl of Total cereal for breakfast. The company says it supplies 100% of the recommended dietary allowance of iron, which I am taking as 18 mg. I know the iron particles are simply mixed in with the cereal, which can be attracted to a magnet.
Would an MRI pick up the fact that you had eaten Total cereal? Is there a magnet that could jiggle the cereal in your stomach, or even have it distend visibly?
Just wondering.
Normally they are so dispersed into the cereal a magnet will not pick them up but if the fortified iron particles clump together they can be picked up.
See this video
IF it was detectable and you went into an MRI, I would guess that the iron detection would be rather unpleasant for the person. There’s a reason people with metal plates on their skull can’t go in.
I was wondering if any of the mad-scientist magnet physicists around here could figure out the proper flux…
Uh… Does an MRI detect that you have blood? Conventional wisdom says there’s iron in there too. (Assuming you’re not one of those types with the copper-based blood.)
Is it just ferrous metals that you can’t have in your body if you have an MRI? What about all the dental metal some people have in their mouth? That doesn’t seem to stop anyone from having an MRI.
It’s magnetic materials that are the problem with an MRI.
So that includes ferrous iron, cobalt, nickel and if you really want to have fun, holmium.
Stainless steels that are not ferromagnetic will be fine. They have FCC crystal structure (ironically because they contain nickel) Plenty of other metals will be ok too.
ETA Ironically wasn’t supposed to be a pun.
That’s ironic…
Amalgam is mercury, silver, tin, copper, etc. don’t think they’re ferrous enough, but the one time I was in an fMRI room my jaw wasn’t horribly shattered so I think it’s ok.
Forgot to mention…
Iron in breakfast cereals is in the form of iron compounds. Most are Fe2+ ionic compounds. Fe3+ occurs less frequently in biological compounds and is more difficult to digest. I think it follows quite a different metabolic pathway.
In either case, these are salts. They are able to dissolve. They are non-metals. They are not ferromagnetic – in fact they have none of the properties of metals. You aren’t going to detect them with an MRI.
Now, if you added some iron filings to your breakfast cereal they would show up on an MRI. But you wouldn’t be able to digest them in any appreciable quantity. We just don;t have the metabolism for digesting metals.
No, iron is present in cereal as reduced (metallic) iron. Separating it out using magnets is a popular classroom exercise.
As Colophon says, they really do put iron powder in cereals. I imagine you wouldn’t digest much of an iron bolt if you swallowed one, but very finely powdered iron is going to react quite quickly and completely with stomach acid to form FeCl2.
Is FeC12 magnetically inert, then?
Is there such a thing as non-ferrous iron? 
From Iron - Health Professional Fact Sheet
Supplemental iron is available in two forms: ferrous and ferric. Ferrous iron salts (ferrous fumarate, ferrous sulfate, and ferrous gluconate) are the best absorbed forms of iron supplements [64]. Elemental iron is the amount of iron in a supplement that is available for absorption. Figure 1 lists the percent elemental iron in these supplements.
FeCl[sub]2[/sub], iron (II) chloride, and yes for present purposes. Many substances are very weakly magnetic whether para- or dia-, but although some compounds are ferromagnetic, iron chloride isn’t one of them.
In high school our AP Chem teacher did an experiment where he took a a box of total, emptied it into a big container, and then used a heavy magnet underneath to gather all of the iron. What was pulled down to the bottom looked like one of those kids games where you use the magnetic wand to add hair to a face (does anybody else remember these?).
Yes and no.
While ferrous materials are certainly the worst kind of metal to have in an MRI (and if the piece of metal is large enough, just being in the room is a serious hazard,) other metals can still pose their own set of problems.
So I gather that, in answer to my question, there is such a thing as ferrous iron compounds.
Ferric iron.
In other words, whether the ion is Fe2+ or Fe3+, as suggested but not outright stated above. This definition of ferrous is different that is used in other realms.