Foods containing ascorbic acid like citrus fruits, broccoli & other dark green vegetables because a scorbic acid reduces iron from ferric to ferrous forms, which increase s its absorption .
Foods containing muscle protein enhance iron absorption due to the effect of cysteine containing peptides released from partially digested meat, which reduces ferric to ferrous salts and form soluble iron complexes.
EDTA ( Ethylene Diamine Tetra-Acetate) molecule has 4 negative charges to which any metal can be attached to form stable complex. The metal incorporated into EDTA can be replaced by a metal of higher affinity or released at a certain PH.
Food is usually fortified by both Fe-EDTA & Na or Ca EDTA.
Fe EDTA is stable in the acidic PH of the stomach, but dissociate in the alkaline PH of the duodenum releasing ferrous ions ready to be absorbed. w hile the Na-Ca EDTA dissociate in the stomach releasing Na & Ca and taking iron from the food instead to form Fe EDTA which dissociate in the duodenum.