Rare (but not outlandish) warning - A friend's entire family had ongoing symptoms of fatigue and upset stomach. They ran blood panels and found that everyone had off the charts iron levels. They had switched to cast iron only in the kitchen a few years back, and switching to stainless pans solved the problem.

I wonder if they were scouring the cast iron every time they cleaned it? Normally a layer of carbon "seasoning" develops and I would think that would limit the direct contact of food and iron.

I clean my cast iron pans with hot water and a brush or scraper only. No detergent (or maybe a small amount to break up oil if I cooked something really greasy). No scouring.