Iron is a mineral that the body needs to produce red blood cells. When the body does not get enough iron, it cannot produce the number of normal red blood cells needed to keep you in good health. Much of the iron in the body is attached to hemoglobin molecules in red blood cells, thereby delivering oxygen to all of the tissues. Myoglobin are heme-containing proteins that are involved in the transport and storage of oxygen. Hemoglobin is the primary protein found in red blood cells and represents about two thirds of the body's iron. The body recycles iron. When red blood cells die, the iron in them is returned to the bone marrow to be used again in new red blood cells.

Iron is mostly stably incorporated in the inside of metalloproteins, because in exposed or in free form it causes production of free radicals that are generally toxic to cells. Iron distribution is heavily regulated in mammals. The iron absorbed from duodenum binds to transferrin, and carried by blood it reaches different cells. There it gets by an as yet unknown mechanism incorporated into target proteins. Good sources of dietary iron include meat, fish, poultry, lentils, beans, leaf vegetables, tofu, chickpeas, black-eyed pea, strawberries and farina.

What is Iron?
Iron, one of the most abundant metals on Earth, is essential to most life forms and to normal human physiology. Iron is an integral part of many proteins and enzymes that maintain good health. In humans, iron is an essential component of proteins involved in oxygen transport. It is also essential for the regulation of cell growth and differentiation. A deficiency of iron limits oxygen delivery to cells, resulting in fatigue, poor work performance, and decreased immunity. On the other hand, excess amounts of iron can result in toxicity and even death.

Almost two-thirds of iron in the body is found in hemoglobin, the protein in red blood cells that carries oxygen to tissues. Smaller amounts of iron are found in myoglobin, a protein that helps supply oxygen to muscle, and in enzymes that assist biochemical reactions. Iron is also found in proteins that store iron for future needs and that transport iron in blood. Iron stores are regulated by intestinal iron absorption

Deficiency Symptoms
Lack of iron may lead to unusual tiredness, shortness of breath, a decrease in physical performance, and learning problems in children and adults, and may increase your chance of getting an infection. Iron deficiency develops gradually and usually begins with a negative iron balance, when iron intake does not meet the daily need for dietary iron. Significant deficiency in iron leads to anemia. The most common symptoms of anemia are weakness and fatigue. Iron deficiency ranges from iron depletion, which yields little physiological damage, to iron deficiency anemia, which can affect the function of numerous organ systems. Iron depletion causes the amount of stored iron to be reduced, but has no affect on the functional iron. However, a person with no stored iron has no reserves to use if the body requires more iron. Iron deficiency in men and women past menopause usually is related to abnormal bleeding, such as from stomach ulcers or colon cancer. Iron deficiency anemia is the final stage of iron deficiency. When the body has sufficient iron to meet its needs (functional iron), the remainder is stored for later use in the bone marrow, liver, and spleen.

Who may need extra iron to prevent a deficiency?
Three groups of people are most likely to benefit from iron supplements: people with a greater need for iron, individuals who tend to lose more iron, and people who do not absorb iron normally. These individuals include:

Where it is found
High levels of iron can come from taking iron supplements or eating too much of foods rich in iron, like red meat. Food contains two types of iron: heme iron and nonheme iron. Heme iron is derived from hemoglobin, the protein in red blood cells that delivers oxygen to cells. Heme iron is found in animal foods that originally contained hemoglobin, such as red meats, fish, and poultry. Iron in plant foods such as lentils and beans is arranged in a chemical structure called nonheme iron. Nonheme iron is absorbed better when it is consumed with animal protein and with vitamin C. Heme iron is absorbed much better than nonheme iron.

The best dietary sources of iron are liver and other organ meats, lean red meat, poultry, fish, and shellfish (particularly oysters). Iron from these sources is readily absorbed in the intestines. Other sources of iron include dried beans and peas, legumes, nuts and seeds, whole grains, dark molasses, and green leafy vegetables. Ferrous sulfate is the most common type of iron supplement. Other available forms include ferrous fumarate, ferrous succinate, ferrous gluconate, ferrous lactate, ferrous glutamate, and ferrous glycine.

Benefits / uses
Iron is essential to most life forms and to normal human physiology. Iron (Fe) is a necessary mineral for the proper function of hemoglobin, the protein in red blood cells that carries oxygen. Iron is also needed for proper muscle and organ function.
Hemoglobin or haemoglobin is the iron-containing oxygen-transport metalloprotein in the red cells of the blood in the body. In each subunit of a hemoglobin molecule, there is a heme group. A heme group consists of an iron atom held in a heterocyclic ring, known as a porphyrin. This iron atom is the site of oxygen binding. The iron atom binds equally to all four nitrogens in the center of the ring, which lie in one plane. In adult humans, the most common hemoglobin is a tetramer (contains 4 subunit proteins) called hemoglobin A, consisting of two α and two β subunits noncovalently bound. The subunits are structurally similar and about the same size.

Iron is an integral part of many proteins and enzymes that maintain good health. In the body, iron is needed to form myoglobin, a protein in muscle cells, and it is essential for certain enzymes that drive the body's chemical reactions. Myoglobin is the putative protein that causes acute renal failure in rapid breakdown of muscle (e.g. rhabdomyolysis, severe crush trauma, malignant hyperthermia, status epilepticus and neuroleptic malignant syndrome), due to its toxicity to renal tubular epithelium. A class of non-heme iron proteins is responsible for a wide range of functions within several life forms, such as enzymes methane monooxygenase (oxidizes methane to methanol), ribonucleotide reductase (reduces ribose to deoxyribose; DNA biosynthesis), hemerythrins (oxygen transport and fixation in marine invertebrates) and purple acid phosphatase (hydrolysis of phosphate esters). When the body is fighting a bacterial infection, the body sequesters iron in the transporter protein transferrin so it cannot be used by bacteria. Inorganic iron involved in redox reactions is also found in the iron-sulfur clusters of many enzymes, such as nitrogenase (involved in the synthesis of ammonia from nitrogen and hydrogen) and hydrogenase. Iron binds avidly to virtually all biomolecules so it will adhere nonspecifically to cell membranes, nucleic acids, proteins etc.

Doses
RDA for iron varies considerably based on the age, gender, and source of dietary iron (heme-based iron has higher bioavailability). Normal daily recommended intakes in milligrams (mg) for iron are generally defined as follows.

Infant birth to 3 years of age 6–10 mg
Children 4 to 6 years of age 10 mg
Children 7 to 10 years of age 10 mg
Children 9 to 13 years: 8 mg
Males 14 to 18 years: 11 mg
Females 14 to 18 years: 15 mg
Males 19 years and older: 8 mg
Females 19 to 50 years: 18 mg
Females 51 years and older: 8 mg
Pregnant females 17–22 mg
Breast-feeding females 15 mg

Possible Side effects / Precautions / Possible Interactions:
The most common side effect from iron supplements is stomach upset including discomfort, nausea, diarrhea, constipation, and heartburn. Stools commonly become dark green or black when iron preparations are taken by mouth. This is caused by unabsorbed iron and is harmless. Do not take iron supplements and antacids or calcium supplements at the same time. It is best to space doses of these 2 products 1 to 2 hours apart, to get the full benefit from each medicine or dietary supplement.

Excessive dietary iron is toxic, because excess ferrous iron reacts with peroxides in the body, producing free radicals. Excess iron consumed all at once causes vomiting, diarrhea, and damage to the intestine. When iron is in normal quantity, the body's own antioxidant mechanisms can control this process. In excess, uncontrollable quantities of free radicals are produced. The lethal dose of iron in a two year old is about three grams of iron. One gram can induce severe poisoning. There are reported cases of children being poisoned by consuming between 10-50 tablets of ferrous sulfate over a few hour period. Overconsumption of iron is the single highest cause of death in children by unintentional ingestion of pharmaceuticals. The DRI lists the Tolerable Upper Intake Level (UL) for adults as 45 mg/day. For children under fourteen years old the UL is 40 mg/day. If iron intake is excessive a number of iron overload disorders can result. Hemochromatosis, hemosiderosis, polycythemia, and iron-loading anemias (such as thalassemia and sickle cell anemia) are conditions involving excessive storage of iron. For this reason, people shouldn't take iron supplements unless they suffer from iron deficiency and have consulted a doctor. Blood donors are at special risk of low iron levels and are often recommended to supplement their iron intake.

When To Take/Types To Take
Iron supplements are best taken with a meal.

Ferrous type iron (e.g. ferrous sulfate) is much better absorbed than ferric iron (e.g.) ferric citrate). The most common form of iron supplement is ferrous sulfate but it is likely to produce intestinal side effects such as constipation. Other forms of iron supplements, such as ferrous fumarate ferrous gluconate, heme iron concentrate, and iron glycine amino acid chelate are readily absorbed and less likely to cause intestinal side effects.

Research studies / References