Bioavailable iron tests?

[Daniel C.]

My friends and I are curious about the amount of iron that gets into food when using a cast iron skillet. Are there any DIY tests for bio-available iron (preferably one that is quantifiable rather than a simple "yes/no iron is here") that we could use?

Also what skillet-cookable foods have zero iron content? I'd rather not have to run two batches of tests, one with and without the iron skillet, especially because that introduces potentially confounding variables.

Thanks,

Dan

[Jeff Backstrom]

You're looking for differences in the part-per-million range (PPM), which is the realm of ICP-OES and (with better detection limits) ICP-MS. You might find a local lab that will do it for $20-40 per element per test. Can't think of anything that you can homebrew that'll give you the precision and accuracy you'll need for something like that.

As for a control, you could use anything coated in PTFE. Aluminum may have some nominal amount of iron in it, and although the amount that would transfer over would be orders of magnitude less than what is likely already there (given that both plants and animals that would be cooked intrinsically contain iron), it would be difficult to account for it.

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[Gordana Ostojic]

It seems that iron deficiency is a big problem in developing world, and it is tackled with cooking acidic food in iron skillets. I remembered that so I googled, and check out http://goaskalice.columbia.edu/answered-questions/does-cooking-cast-iron-pots-and-pans-add-iron-our-food and http://www.ncbi.nlm.nih.gov/pubmed/12859709 . It seems that the amount is 0.5 % which is huge much more than what you would need for icp. 

I would suggest to follow the articles and see how they measured though.

  

[Mike Horwath]

Hi Dan,

Interesting project! Here's a few thoughts:

• I agree with Jeff, I don't think there's any easy DIY tests for iron content. If you have a nearby university with a chemistry department, you may be able to strike up a collaboration...they could potentially get a quick publication out of it.
• "Bio-available iron" is a complex concept. Fe2+, Fe3+, and Heme iron are all absorbed, but with different efficiency that is further affected by acidity, phytate, etc. Most nutritional information just gives the total iron even though it can be misleading.
• You'll have a hard time finding zero iron content food, but most fruits and starchy foods are pretty low unless they are iron fortified.  You could go with polenta for example.
• There is a small amount of research published on this subject, but it definitely looks like an area that needs more work.  Here is a search on pubmed...
• http://www.ncbi.nlm.nih.gov/pubmed/?term=Iron+content+of+food+cooked+in+iron+utensils.

Mike

[Jake]

http://www.ncbi.nlm.nih.gov/pubmed/19476680

Cooking three typical refugee dishes in stainless steel pots led to an increase in Fe content of 3.2 to 17.1 mg/100 g food (P < 0.001).

Here is a review article...

http://www.ncbi.nlm.nih.gov/pubmed/23868537

Looks like most studies simply have people eat from iron pots and then measure their blood hemoglobin change.  Kind of a nifty way to do it.