If I am not mistaken there's no definitive answer. It seems that it does in some cases but not all. Older Research: http://www.ncbi.nlm.nih.gov/pubmed/12859709Article on a Vegan Site: http://www.veganhealth.org/articles/ironOne of those "lovely" myths debunked posts with no sources or citations (Entry 5): http://www.thekitchn.com/5-myths-of-cast-iron-cookware-206831
As the citationless link that Tiago Souza gave us points out, it will vary depending on the degree that the pan is "seasoned" (I would imagine pans 1200 years ago would be quite valuable, handed down between generations, and not accustomed to harsh detergents or dishwashers, so we can probably assume they're fairly well seasoned) and also the acidity of the food. This makes a fair amount of sense, although I imagine that most of the staple diet wasn't particularly acidic. Its quite possible that the "workaround" was that the poor just _were_ quite anaemic - and probably had a number of other nutritional deficiencies to boot. Jamie, is your forensic pathologist friend still a listener? I doubt anaemia would show up in bone structure but some other nutritional deficiencies might. Just the average size of skeletons might give an indicator, although I suspect that that is partially genetic.