During the 1920's an animal model for iron deficiency research was created by feeding rats on an exclusive milk diet. In a healthy adult human there is 3 to 5 gms of iron. The newborn infant has nearly double the amount of iron per kg than adults. Sixty to 70 percent of tissue iron is classed as essential or functional iron, and 30 to 40 Percent as storage iron. Heme iron from meat is 10 percent available for absorption while iron from fresh plant sources are only one percent available because of phytates.
Absorption takes place primarily in the duodenum where the intestinal environment is still acid.
Symptoms of iron deficiency include listlessness, fatigue, heart palpitations on exertion, reduced cognition, memory deficits, sore tongue, angular stomatitis, dysphagia, hypochromic microcytic anemia. Stomach hydrochloric acid is required for optimal absorption of iron, ascorbic acid increases absorption of iron, clays and phytates decrease absorption of iron, The RDA of 18 mg per day as metallic iron is very low if one is a vegan eating high fiber, high phytate plant material. Iron can cause cirrhosis of the liver, fibrosis of the pancreas, diabetes and heart failure - these diseases are not direct affects of iron per se, but rather the increased iron causes increased needs for selenium, copper, zinc, etc.