Iron in the Human Body
Approximately 70% of the iron found in the human body is defined as functional. The remainder can be subdivided into transport iron and storage iron. 80% of functional iron can be found in red blood cells, in the compound hemoglobin; the remaining 20% is found in myoglobin and intracellular respiratory enzymes such as cytochromes. 70-80% of storage iron is stored as ferritin in the liver, bone marrow, spleen, and skeletal muscles; a portion of the body's iron is stored instead as hemosiderin. Iron is transported through the bloodstream by the protein transferrin.
The amount of iron in the human body is regulated and balanced by gastrointestinal absorption, which maintains the amount of functional iron and establishes the ferritin and hemosiderin stores. The body's capacity for absorption is affected by the amount of iron that has already been stored, the body's rate of red blood cell production, the amount and kind of iron present in the body's diet, and the amount and kind of enhancer and inhibitor chemicals related to iron absorption present in said diet. Heme iron, present in meat, poultry, and fish, is 2 to 3 times more absorbable than non-heme iron, present in plant-based and iron-fortified foods. Beef liver, clams, oysters, red meats (preferably lean), kidneys, and eggs are all strong sources of heme iron; beans, wheat germ, whole grains, peas, nuts, dried fruits, leafy green vegetables (such as spinach), and of course food which has been fortified are all strong sources of non-heme iron. The chief enhancers for the absorption of non-heme iron are heme iron and vitamin C. Vitamin C can be found in broccoli, tomatoes, sweet potatoes and white potatoes, cantaloupe and citrus fruits. The chief inhibitors for the absorption of both heme and non-heme iron are polyphenols (found in certain vegetables), tannins (found in tea), phytates (found in bran), and calcium (found in dairy products).
The human body recycles iron when it breaks down red blood cells, but it does not retain the iron absolutely. Some (approximately 1 mg) iron gets lost daily in feces, skin cells and mucus, and a miniscule amount is lost through gastrointestinal blood loss. pathological losses of iron can frequently be attributed to sensitivity to cow's milk, peptic ulcer disease, inflammatory bowel disease, bowel cancer, and hookworm infections. Women of child-bearing age lose iron in their menses, averaging out to .3-.5 mg daily in those years. Women lose more iron during and after pregnancy, averaging out to 3 mg daily in that time). It therefore should not be surprising that women of child-bearing age are one of the demographics at highest risk for iron deficiency. Within that demographic category, women with minority ethnic backgrounds and/or who are from lower income brackets are at even higher risk.
SOURCES USED FOR THIS WRITEUP: www.cdc.gov/epo/mmwr/preview/mmwrhtml/00051880.htm, www.goaskalice.columbia.edu/0712.html.