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Part II Nutrition Assessment, Consequences, and Implications

is normally tightly regulated according to body needs. The mechanism is not known, although iron seems to enter the body through the gastrointestinal tract, spe- cifically the duodenum. Since iron is recycled within the body, limited iron is excreted with only a small amount of dietary iron absorbed. Active erythro- poiesis and/or iron deficiency upregulates absorp- tion; iron overload downregulates absorption (3). Many older adults have undiagnosed nutritional

anemias. Anemia is a significant clinical finding, and efforts should be made to determine its etiology (3-4). Anemia is classified on the basis of the etiol- ogy (1,4,10) and is generally defined as a deficiency in erythrocyte mass and hemoglobin contents. A low hemoglobin or hematocrit value needs to be evalu- ated further by a complete blood cell count, which includes hemoglobin concentration, hematocrit value, RBC mass, and mean corpuscular volume (MCV) (2,5). Normal ranges for these laboratory tests are listed in Table 11.2 (5,11). Normal laboratory values can be altered for several reasons, including disease

states and medication side effects (6). The common reasons for altered lab results that relate to anemia are listed in Table 11.3 (see pages 166–167). Even in healthy aging, there is a gradual drop in RBC indexes and a trend toward lower hemoglobin levels after age 60 in both men and women. This is accompanied by a decrease in RBCs (12,13). A mild normochromic anemia with hemoglobin levels between 11 and 12 g/dL in adults older than 70 years, with no identified underlying pathology, can be a common finding (4).

CLASSIFICATION OF ANEMIAS The most common system for organizing anemia is by identifying the underlying cause. The causes include blood loss, deficient erythropoiesis, and excessive hemolysis (14).

Blood loss anemias can result from acute or chronic blood loss. Identification of the cause of the blood loss and resolution of the loss will most likely resolve the anemia. The lost erythrocyte mass and

TABLE 11.2 Normal Values for Laboratory Tests for Anemia Normal Value

Laboratory Test Hemoglobin, g/dL Hematocrit, %

Mean corpuscular volume, mm3 Mean corpuscular hemoglobin, pg/cell

Mean corpuscular hemoglobin concentration, g/dL Serum iron, mg/dL Ferritin, ng/mL

Transferrin mg/dL

Total iron binding capacity, mg/dL Serum folate, mg/mL

Serum vitamin B-12, pg/mL Homocysteine, mmol/L

Source: Data are from references 5 and 11.

Male 14–18 42–52 80–95 27–31 32–36

80–180 12–300 215–365 250–420 5–25

160–950 4–14

Female 12–16 37–47 80–95 27–31 32–36

60–190 10–150 250–380 250–420 5–25

160–950 17–76