Magnitude and nature of the problem

Iron deficiency is one of the most common nutrient deficiencies worldwide and affects young children and women of reproductive age in both developed and developing countries. It is a dynamic process that begins with depletion of iron stores, leading finally to anemia (Fig. 22.1), which is characterized by low hemoglobin levels and is associated

From: Nutrition and Health: Handbook of Nutrition and Pregnancy Edited by: C.J. Lammi-Keefe, S.C. Couch, E.H. Philipson © Humana Press, Totowa, NJ

• Iron depletion

Reduction of iron stores

■ Serum ferritin

T Total iron binding capacity (TIBC)

• Iron-deficient erythropoiesis

Exhaustion of iron stores

  • Serum iron
  • Transferrin saturation

T Free erythrocyte protoporphyrin (FEP)

T Serum transferrin receptor concentration

• Iron-deficiency anemia

Exhaustion of iron stores and microcytic, hypochromic erythrocytes

  • Hemoglobin
  • Hematocrit

Fig. 22.1. Stages of iron deficiency with several functional consequences such as low birth weight, impaired cognition, and reduced work performance [1, 2].

The first stage of iron deficiency, known as iron depletion, occurs when iron stores are low and serum ferritin concentrations drop. The second stage, iron-deficient erythropoiesis, occurs when iron stores are depleted and the body does not absorb iron efficiently. Iron-deficient erythropoiesis is characterized by a decrease in transferrin saturation and increases in transferrin receptor expression and free erythrocyte protoporphyrin (FEP) concentration. Iron-deficiency anemia (IDA) is the third and most severe stage of iron deficiency and is characterized by low hemoglobin and hematocrit values. Erythrocytes are hypochromic and microcytic during IDA and hemoglobin concentration falls below -2 standard deviations of the age- and sex-specific normal reference. Anemia is the most widely used indicator of iron deficiency in most settings. The World Health Organization (WHO) reference values for anemia are hemoglobin < 11 g/dl for pregnant women and children under 5, < 12 g/dl for nonpregnant women, and < 13 g/dl for men [3].

Anemia is a highly prevalent public health problem that affects more than 2 billion people worldwide, and an estimated 50% of anemia is caused by iron deficiency [4, 5]. Pregnant women are particularly vulnerable to developing anemia and an estimated 18 and 56% of pregnant women are anemic in industrialized and developing countries, respectively (Table 22.1). WHO classifies the public health significance of anemia based on national anemia prevalence estimates and, as evidenced by the prevalence rates in Table 22.1, anemia in pregnant women and children is a severe public health problem (anemia prevalence > 40%) in regions such as Africa, the Eastern Mediterranean, and South-East Asia [3].

Although iron deficiency is the most common cause of anemia, there are other nutritional and non-nutritional causes of anemia [6]. As illustrated in Fig. 22.2, not all anemia is caused by iron deficiency, and not all iron deficiency results in anemia. For example, inadequate intakes of folate and vitamin B12 can also cause anemia. Infections and genetic abnormalities such as thalassemia may also contribute to anemia in some populations. One of the major limitations of understanding how much anemia can be attributed to iron deficiency is the lack of data on the causes of anemia in many developing countries.

Table 22.1

Prevalence of Anemia in Developing and Industrialized Countries and in World Health Organization (WHO)-Classified Regions [4, 5]

Table 22.1

Prevalence of Anemia in Developing and Industrialized Countries and in World Health Organization (WHO)-Classified Regions [4, 5]

Pregnant

Nonpregnant

School-age

women (%)

women (%)

children (%)

Industrialized countries

18

12

9

Developing countries

56

44

53

WHO regions

Africa

51

52a

Americas

35

23a

South-East Asia

75

63a

Europe

25

22a

Eastern Mediterranean

55

45a

Western Pacific

43

21a

aFive- to 14-year-olds

Poor iron intake, low dietary iron bioavailability, pregnancy, menorrhagia, parasitic infections

Iron Deficiency

IDA "

Anemia "

Anemia caused by iron deficiency

B12, folate, or vitamin A deficiency, parasitic infections such as malaria and hookworm, genetic abnormalities

Poor iron intake, low dietary iron bioavailability, pregnancy, menorrhagia, parasitic infections

Anemia caused by iron deficiency

B12, folate, or vitamin A deficiency, parasitic infections such as malaria and hookworm, genetic abnormalities

Fig. 22.2. Etiology of anemia

The assumption that 50% of anemia seen in many developing countries is due to iron deficiency is often based on small, nonrepresentative samples, and recent studies indicate that the contribution of iron deficiency to anemia may be overestimated in certain parts of the world. Understanding the etiology of anemia is very important in the development of appropriate public health strategies. Despite considerable efforts since the 1960s, anemia continues to be a problem in many parts of the world and progress in the reduction of iron deficiency and anemia has been less than satisfactory [7]. Interventions aimed at improving iron status, such as supplementation, may not necessarily reduce all forms of anemia and its related consequences in some populations. Similarly, relying only on hemoglobin as an indicator of response for programs that aim to prevent and control iron deficiency may be inadequate.

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