Iron is critical to human life. It plays the central role in the hemoglobin molecule of our red blood cells (RBC), where it functions in transporting oxygen from the lungs to the body's tissues. It also functions in several key enzymes in energy production and metabolism, including DNA synthesis.
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 up to 30-50 percent of people in these groups. For example, some degree of iron deficiency occurs in 35-58 percent of young, healthy women. During pregnancy, the number is even higher.
What Causes Iron Deficiency?
Iron deficiency may be caused by a variety of factors. Increased requirements for iron occur during the growth spurts of infancy and adolescents, so these groups may be especially at risk. Unfortunately, typical infant diets in developed countries (high in milk and cereals) are low in iron, as are typical adolescent "junk food" diets. The population at greatest risk for an iron-deficient diet, however, is low-income seniors. This is complicated by the fact that decreased absorption of iron-often due to a lack of hydrochloric acid production in the stomach-is extremely common in the elderly.
Menstrual blood loss is well recognized as a major cause of iron deficiency anemia in fertile women. However, what is not as well known is that chronic iron deficiency can be a cause of excessive menstrual blood loss, a condition known as menorrhagia. It has been suggested that iron deficiency leads to menorrhagia based on several observations, with the most important being that iron supplementation often produces a dramatic decrease in menstrual blood loss. In one double blind, placebo-controlled study, 75 percent of women on iron supplementation had significant reduction of menorrhagia compared with only 32.5 percent for the placebo group.
Iron supplementation, at a daily dose of 100 mg elemental iron, has been recommended as a preventive therapy by several researchers, since it appears that chronic iron deficiency may promote menorrhagia, and iron-containing enzymes in the uterus are depleted before changes in red blood cell numbers or hemoglobin are observed.
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. For these reasons the recommended daily intake of iron during pregnancy is 60 mg. Since this typically cannot be achieved by dietary means, supplementation is required.
And the need for additional iron doesn't stop when the baby is delivered. Typically the mother will lose approximately 150-300 mg of iron due to hemorrhage and blood loss during delivery. In addition, lactation causes an additional drain of iron stores. For these reasons it is important for women to continue to take iron supplements throughout their pregnancy and nursing period.
Iron Deficiency Symptoms & Diagnosis
The negative effects of iron deficiency are due largely to the impaired delivery of oxygen to the tissues and the impaired activity of iron-containing enzymes in various tissues. The symptoms of anemia, such as extreme fatigue, reflect a lack of oxygen being delivered to tissues and a build-up of carbon dioxide.
While iron deficiency is the most common cause of anemia, it must be pointed out that anemia is the last stage of iron deficiency. Iron dependent enzymes involved in energy production and metabolism are the first to be affected by low iron levels. Several researchers have clearly demonstrated that even a slight iron deficiency leads to a reduction in physical work capacity and productivity. Supplementation with iron has shown rapid improvements in work capacity in iron-deficient individuals.
Even marginal iron deficiency can also significantly impair immune function. Iron deficiency greatly reduces the immune system's ability to fight off infection, and can also lead to 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.
Iron deficiency is also associated with impaired brain function, including markedly decreased attentiveness; less complex or purposeful, narrower attention span; decreased persistence; and decreased voluntary activity. These symptoms can be especially present in children, making iron deficiency a leading contributor to learning disabilities. Fortunately, with iron supplementation there is a return to normal mental function.
If you notice any of these symptoms and suspect that you may have an iron deficiency, there are several tests you can undergo. The most sensitive by far is a blood test that measures serum ferritin, the iron storage protein. Other measures of iron stores-such as serum iron, total iron binding capacity, and hemoglobin-are less sensitive, but often performed on a routine basis. Long-term iron deficiency is characterized by anemia with low red blood cell (RBC) levels, low hematocrit (volume of red blood cells), small RBCs, and low serum ferritin levels.
Treating Iron Deficiency with Diet & Supplements
The best dietary source of iron is red meat, especially liver. Other good sources include fish, beans, molasses, dried fruits, whole grain and enriched breads, and green leafy vegetables (see "Dietary Sources of Iron" below).
Regardless of diet, iron supplementation is often required to raise levels, especially during pregnancy and in young menstruating women. Ferrous sulfate is the most popular supplement, but it is less than ideal, as it often causes constipation or other gastrointestinal (GI) disturbance. Although it's best absorbed when taken on an empty stomach, doing so often causes nausea or GI upset. So it's most often taken with food, which greatly reduces its absorption. Currently, the best sources of iron in supplements appear to be a special form of ferric pyrophosphate and ferrous bisglycinate. Both are free from gastrointestinal side effects with a high relative bioavailability, especially if taken on an empty stomach.
For iron deficiency, up to 60 mg daily in divided doses may be recommended. For general health purposes, the RDA should be used as a supplementation guideline (see RDA chart, p. 34). High intakes of other minerals, particularly calcium, magnesium, and zinc can interfere with iron absorption, so when treating iron deficiency, try to take iron without these minerals. In contrast, vitamin C enhances iron absorption.
Keep all iron supplements out of the reach of children. Acute iron poisoning in infants can result in serious consequences. Severe iron poisoning is characterized by damage to the intestinal lining, liver failure, nausea and vomiting, and shock.
Easy Iron comes in a chewable tablet form and has 20 mg of highly absorbable iron (as ferric pyrophosphate).
Gentle Iron capsules feature 25 mg of iron bisglycinate, a non-constipating form of iron. There's no gluten, wheat, or dairy.
Chelated Iron 27 mg has ferrous bisglycinate chelate iron from Albion Minerals, a leader in bioavailable chelated minerals.
Dietary Sources of Iron
The table below provides the iron content per serving of some of the better food sources of iron, but it does not factor in absorption rates. For example, the absorption rate for calf's liver is nearly 30 percent while the absorption rate for the vegetable sources is approximately 5 percent.
Average serving size (g)
mg. iron per serving
Calf or lamb liver
Beef or chicken liver
Bread (3 slices)
Chicken or turkey
Recommended Dietary Allowances (RDA) for Iron
Infants (7 months) up to age 10
Males 11–18 years old
Males 19 years and older
Females 11 years and older