Iron is an essential element for blood production. About 70 percent of your body's iron is found in the red blood cells of your blood called hemoglobin and in muscle cells called myoglobin. Hemoglobin is essential for transferring oxygen in your blood from the lungs to the tissues. Myoglobin, in muscle cells, accepts, stores, transports and releases oxygen.

About 6 percent of body iron is a component of certain proteins, essential for respiration and energy metabolism, and as a component of enzymes involved in the synthesis of collagen and some neurotransmitters. Iron also is needed for proper immune function.

About 25 percent of the iron in the body is stored as ferritin, found in cells and circulates in the blood. The average adult male has about 1,000 mg of stored iron (enough for about three years), whereas women on average have only about 300 mg (enough for about six months). When iron intake is chronically low, stores can become depleted, decreasing hemoglobin levels.

When iron stores are exhausted, the condition is called iron depletion. Further decreases may be called iron-deficient erythropoiesis and still further decreases produce iron deficiency anemia.

Blood loss is the most common cause of iron deficiency. In men and postmenopausal women, iron deficiency is almost always the result of gastrointestinal blood loss. In menstruating women, genitourinary blood loss often accounts for increased iron requirements. Oral contraceptives tend to decrease menstrual blood loss, whereas intrauterine devices tend to increase menstrual bleeding. Other causes of genitourinary bleeding and respiratory tract bleeding also increase iron requirements.

For blood donors, each donation results in the loss of 200 to 250 mg of iron. During periods of growth in infancy, childhood and adolescence, iron requirements may outstrip the supply of iron from diet and stores. Iron loss from tissue growth during pregnancy and from bleeding during delivery and post partum averages 740 mg. Breastfeeding increases iron requirements by about 0.5 to 1 mg a day.

Iron Requirements

Your "iron level" is checked before each blood donation to determine if it is safe for you to give blood. Iron is not made in the body and must be absorbed from what you eat. The adult minimum daily requirement of iron is 1.8 mg. Only about 10 to 30 percent of the iron you consume is absorbed and used by the body.

The daily requirement of iron can be achieved by taking iron supplements. Ferrous sulfate 325 mg, taken orally once a day, and by eating foods high in iron. Foods high in vitamin C also are recommended because vitamin C helps your body absorb iron. Cooking in iron pots can add up to 80 percent more iron to your foods. Consult with your primary care provider before taking iron supplements.