Iron— The Most Common Nutrient Deficiency in the U.S.

Iron deficiency is the most common nutrient deficiency in the United States. The groups at highest risk are
infants under two years of age, teenage girls, pregnant women and the elderly. Studies have found evidence of iron deficiency in as high as 30 to 50 per- cent of people in these groups. Here is an alarming fact: some degree of iron deficiency occurs in 35 to 58 percent
of young, healthy women. During preg- nancy, the number is even higher.
Iron deficiency has serious conse- quences. It is critical to human life for several reasons. Most notably, it plays the central role in the hemoglobin mol- ecule of our red blood cells (RBC) where it functions in transporting oxygen from the lungs to the body’s tissues and the transportation of carbon dioxide from
the tissues to the lungs. Iron also func- tions in several key enzymes in energy production and metabolism including DNA synthesis.
What causes iron deficiency?
Iron deficiency may be due to an increased iron requirement, decreased dietary intake, diminished iron ab- sorption or utilization, blood loss or a combination of factors.
Increased requirements for iron occur during the growth spurts of infancy and adolescents, and during pregnancy and lactation. Currently, the vast majority
of pregnant women are routinely given iron supplements during their pregnan- cy.
Inadequate intake of iron is common even in the United States, particularly in
those consuming primarily a vegetarian diet, but the group at greatest risk for
a diet deficient in iron is the elderly population. This decreased intake of iron in the elderly is complicated by the fact that decreased absorption of iron is extremely common the older we get.
Decreased absorption of iron can
be due to a lack of hydrochloric acid secretion in the stomach. Decreased stomach acid production is a fairly common condition in the elderly. Other causes of decreased absorption include chronic diarrhea or malabsorption, the surgical removal of the stomach and antacid use.
Blood loss is the most common cause of iron deficiency in women of child- bearing age. This is most often due to excessive menstrual bleeding. Other common causes of blood loss include bleeding from peptic ulcers, hemor- rhoids and donating blood.
How is iron deficiency diagnosed?
The diagnosis of iron deficiency can best be made by a blood test that mea- sures serum ferritin, the iron storage protein. This is by far the most sensitive test for iron deficiency.
Doesn’t iron deficiency cause anemia?
Anemia refers to a condition in which the blood is deficient in red blood cells or the hemoglobin (iron containing) portion of red blood cells. The primary function of the red blood cell (RBC) is to transport oxygen from the lungs to the tissues of the body in exchange for car- bon dioxide. The symptoms of anemia, such as extreme fatigue, reflect a lack of oxygen being delivered to tissues and a build-up of carbon dioxide.
Iron deficiency is the most common cause of anemia, however, it must be pointed out that anemia is the last stage of iron deficiency. Iron dependent enzymes involved in energy produc- tion and metabolism are the first to be affected by low iron levels.
How much blood do women lose during menstruation?
Women typically lose 40 to 80 ml of blood per period. Heavier periods are definitely associated with negative iron balance in most cases. Negative iron balance means that more blood is lost than is being absorbed from the diet. Iron supplementation is often recom- mended as a preventive therapy against negative iron balance.
Why is the need for iron higher during pregnancy?
During pregnancy, the requirement for iron increases dramatically due to iron contributions to the fetus, placenta and umbilical cord coupled with an increase in red cell mass in the mother. Iron loss in the urine, sweat and feces is also increased. Subsequently, anemia due to iron deficiency is extremely com- mon in pregnancy. For these reasons the recommended daily intake (RDI) of iron during pregnancy 27 mg a day (9 mg a day more than for non-pregnant women). Since this amount is typically not achieved by dietary means, supple- mentation is required. 

Can iron deficiency affect immune function?
Even marginal iron deficiency can significantly impair immune function. Iron deficiency greatly reduces the immune system ability to fight off infection. Common findings in iron de- ficient individuals are increased rate of infections, lymphatic tissue shrinkage, altered white blood cell concentrations, and defective white blood cell function. Iron deficiency may be the responsible factor in many individuals suffering from impaired immune function, chronic infections and frequent colds.
Does iron deficiency decrease mental function?
Virtually any nutrient deficiency can result in impaired brain function, espe- cially in children. Since iron deficiency is the most common nutrient deficiency in American children, it is most important nutritional cause of learning disability.
Iron deficiency is associated with markedly decreased attentiveness; less complex or purposeful, narrower attention span; decreased persistence; and decreased voluntary activity. Fortunate- ly, with iron supplementation there is a return to normal mental function.
Do low iron levels equal low energy levels?
Several researchers have clearly demon- strated that even a slight iron-deficiency leads to a reduction in physical work capacity and productivity. Nutrition surveys done in the U.S. have indicated that iron-deficiency is a major impair- ment of health and work capacity and
as a consequence of this an economic loss to the individual and the country. Supplementation with iron has shown rapid improvements in work capacity in iron-deficient individuals. Impaired phys- ical performance due to iron deficiency is not dependent on anemia. Again, the iron-dependent enzymes involved in energy production and metabolism will be impaired long before anemia occurs.
What are the best dietary sources of iron?
The best dietary sources of iron are red meat, especially liver, oysters, and fish. The form of iron in these foods is heme iron signifying that is complexed with the hemoglobin protein. This form of iron is much better absorbed than non-heme iron found in plant foods. Good non-meat sources of iron include beans, dark chocolate, dried fruits and green leafy vegetables. Non-heme iron absorption is enhanced by vitamin C.
Table 2 provides the iron content per serving of some of the better sources
of iron. The table does not factor in absorption. For example, the absorption rate for calf’s liver is nearly 30 percent while the absorption rate for the vegeta- ble sources is approximately 5 percent. The daily dietary recommended allow- ance for iron is 18 mg for women and 10 mg for men. Iron supplementation is often required to raise iron levels, especially during pregnancy and in young menstruating women. Frequently used forms of iron in supplements include ferrous sulfate, gluconate and gluconate. These salts, especially, ferrous sulfate often cause constipation or other gastrointestinal (GI) disturbance. Although it is best absorbed when taken on an empty stomach, taking ferrous sulfate especial- ly often causes nausea or GI upset. So, it is most often taken with food, which greatly reduces its absorption.
Currently, the best forms of iron supplement appear to be a special form of ferric pyrophosphate and ferrous bisglycinate. Both are free from gastro- intestinal side effects with a high relative bioavailability especially if they are taken on an empty stomach.
What is the usual dosage for iron sup- plements?
For iron deficiency, the usual recom- mendation is up to 60 mg daily in divid- ed doses. For general health purposes, the RDI (recommended daily intake) should be used as supplementation guidelines. High intakes of other miner- als, particularly calcium, magnesium and zinc can interfere with iron absorption, so when treating iron deficiency it is recommended to take iron away from these minerals. In contrast, vitamin C enhances iron absorption.
Cautions and Warnings
Keep all iron supplements out of the reach of children. Acute iron poisoning in infants can result in serious conse- quences. Severe iron poisoning is char- acterized by damage to the intestinal lining, liver failure, nausea and vomiting and shock. 

Iron is critical for human life. Often the dietary intake of iron does not ade- quately satisfy body needs. This occur- rence is particularly common in young menstruating women, and during preg- nancy and lactation. Iron supplementa- tion is recommended at these times and during deficiency. The best forms of iron supplement are ferric pyrophosphate and ferrous bisglycinate.