I love my Cast Iron skillets - have done most of my cooking on them for over 25 years - and was fortunate to learn early on that if you add acidic ingredients (such as tomatoes, or lemon juice, or wine) to your dish and let it cook a few minutes it extracts highly absorbeable, excellent iron and puts it into your food.
Once CI fell out of favor due to stealthy consumer marketing of aluminum (!) and teflon (!) options, the anemia rates - esp in menstruating or pregnant or postpartum women increased to be similar to very malnourished women.
In all the 25 years of cooking with CI, I’ve never once looked or felt anemic - but have advised a good number of others about improving their iron levels with CI (which never constipates, unlike typical nasty iron supplements).
On a different note: once I made the horrid mistake of adding stevia powder to a dish in my CI skillet that I like to sweeten a bit. The stevia took on a horrid metallic taste, and left that taste in the skillet even after a couple of cleanings and other cooking… because of CI’s aborbability which is usually great for spices but awful for stevia powder. Be forewarned!