Seasoned cast iron does NOT release iron into your diet. Once it’s seasoned it’s totally covered in carbon and no iron is in contact with the food. If you let the pan get rusty it will release iron but it will also be one crappy pan to cook with.
http://www.suite101.com/content/cooking-with-cast-iron-pots-a59702
Do a search on cast iron health benefits. Even the Lodge Manufacturing company agrees right before their paragraph on seasoning.