The reason why iron is given added importance in the functioning of the human body is because of its integral part in the respiratory system. It is an important component of hemoglobin, which plays an essential role blood flow, and fulfills the function of conveying oxygen throughout the body. This makes absorption of iron a critical operation.
Iron and Hemoglobin
Hemoglobin is found in the red blood cells of most vertebrates, and some invertebrates. It is a metalloprotein that helps the circulation of oxygen in the body. Hemoglobin is basically made up of proteins and heme, which is basically made up of iron. The conveyance of oxygen and nutrients is done with the help of red blood cells. These cells contain about 97% of the dry blood cell content, which is, of course, quite substantial. 1.36 and 1.37 ml O2 per gram of hemoglobin, can bind oxygen to be carried to the different organs. In short, the prescribed amount of iron is an absolute necessity to keep the supply of oxygen constant throughout the body.
A shortage of iron is known as anemia, where the red blood cells in the human body tend to shrink, and often their number becomes sparse. Iron deficiency can also lead to some other growth-related conditions. In conclusion, one might say that iron is an indispensable constituent of the human body.
Process of Iron Absorption
Absorption of iron in the human body takes place through the digestive tract (the small intestine). The remaining organs of the digestive system contribute their bit to breaking down of food matter. However, the important part comes when the iron from the food source gets assimilated into the blood flow and into the hemoglobin. This process is aptly termed as the 'absorption' of iron, and is initiated by a class of cells termed as enterocytes. These cells are present in the inner glycocalyx surface of the duodenum, of the small intestine. The glycocalyx is an extracellular polymeric surface that is secreted by the cells themselves.
It must be noted that iron that is a part of protein is usually absorbed by the body. This 'absorbable' iron, containing protein, is often referred to as the heme protein. The ferrous form of this protein is chemically represented as Fe2+. Not all dietary irons are in this form, and some of them have to be reduced down from Fe3+. This function is conducted at the 'brush border', where a ferric reductase enzyme (a type of enzyme), duodenal cytochrome B, reduces it down to Fe2+. The process of conversion finishes here, and a protein by the name DMT1, which is also known as divalent metal transporter 1, transports the iron to the cells. There are some very complex procedures that are involved in later stages where the iron optimizes the oxygen-carrying capacity of the hemoglobin. Rare absorption problems might arise in this procedure, which can prove to be very dangerous if left undetected, but can be cured.
Iron, being an important nutrient, is included in many diets and is prescribed by many health departments and agencies. Red meat and poultry products are considered as important sources of iron. Leafy vegetables and fruits are also important sources of iron.