Iron is very important for the formation of red blood cells. 70% of the iron in the body is found in the red blood cells (haemoglobin) and in muscle cells (myoglobin). Hemoglobin is a protein and helps transfer oxygen from the lungs to the body’s tissues. Myoglobin present in tissues of the muscle then accepts, stores, transports and releases oxygen.

There are two kinds of iron in our diets: Heme and nonheme iron. Heme iron is formed from the breakdown of hemoglobin and is only found in animal products.  Nonheme iron is plant-based.

Functions:

Hemoglobin formation:  Iron is the primary component of Hemoglobin which carries oxygen in the blood to the body. Hemoglobin also gives blood its red colour.

Muscle function: Our muscles need iron for their functioning. The iron present in muscle helps in muscular contraction. Myoglobin is a muscle protein that carries oxygen from haemoglobin to the muscle cells.

Brain function:

Iron is important for cognition and healthy brain development and functioning. Iron supplies oxygen to the blood and brain tissues. The brain uses about 20% of the oxygen in our bloodstream. 
 
Deficiencies:

Iron deficiency anemia: Iron deficiency can be caused by lack of dietary iron, not absorbing enough iron or excessive blood loss.  When a person's diet lacks iron, the iron stores in the body are used. This causes iron deficiency anemia.  Resulting in weakness, shortness of breath, dizziness, fatigue, lack of focus and attention, headaches and an increase in sensitivity to cold weather. Very severe deficiency can even lead to renal failure. 

Groups at risk of iron deficiency include menstruating females, pregnant women and toddlers above 6 months of age.  Those who frequently donate blood may experience weakness and mild deficiency. This is why maintaining a gap of 3-4 months between successive blood donations is important. Babies at the weaning stage are at risk for low iron levels if they do not receive the appropriate foods. Semi solid foods should contain iron-rich options. Babies are born with sufficient iron stores to last about six months. At birth a child’s iron needs are met by breast milk. Formula fed infants should be given an iron supplement or iron-fortified infant formula.

Food sources rich in iron include the following:
Liver, Red meat, Chicken, Seafood, Pork, Soybeans, Legumes, Tofu, Spinach, Watermelon, Dates, Raisins and Fortified Foods (cereals). Since vitamin C enhances iron absorption, it is important that foods high in vitamin C are included in the diet. Iron and vitamin C rich foods can be paired together for optimal absorption. 

Note: Since iron plays an important role in brain function, its deficiency is a cause of poor cognition in school-aged children. Yet, later in life, iron overload can cause damage to the brain. Abnormally high iron concentrations have been found in the brains of patients with Alzheimer's and Parkinson's diseases.