NOTE: ✓ = predictive of risk or benefit; ? = evidence unclear; 0 = no evidence, or evidence but no effect; blank = not applicable to that group.
a Within the broad category chronic or recurring infections, there is evidence for nutrition risk and benefit for some specific criteria, such as tuberculosis, but not for other specific criteria, such as upper respiratory infections, bronchitis, and otitis media. The same is true within the broad categories drug-nutrient interactions and food intolerances.
Criteria Related To Nutrient Deficiencies
Anemia is defined as a reduction of the red blood cell (erythrocyte) volume or hemoglobin concentration greater than two standard deviations below the mean (i.e., below the 2.5th percentile) occurring in healthy persons of the same age, gender, or, for women, stage of pregnancy (IOM, 1990, 1993). Anemias are generally classified into two groups—those resulting primarily from decreased production of red blood cells or hemoglobin, or those in which increased destruction or loss of red blood cells is the predominant mechanism. Megaloblastic anemia is associated with deficiencies of folate and vitamin B6 and/or vitamin B12. Microcytic anemia is associated with thalassemia trait, iron deficiency, and/or copper deficiency. The most common nutrition-related anemia is iron deficiency, which may be caused by diets low in iron, the insufficient assimilation of iron from the diet, the utilization of iron for rapid growth or pregnancy, or blood loss.
Prevalence of and Factors Associated with Anemia
Information on the prevalence of iron deficiency anemia in the United States comes from the National Health and Nutrition Examination Surveys (NHANES), conducted by the National Center for Health Statistics; the Pregnancy (PNSS) or Pediatric Nutrition Surveillance System (PedNSS), conducted by the Centers for Disease Control and Prevention (CDC); the U.S. Department of Agriculture's (USDA) WIC Eligibility Study; and the National WIC Evaluation. Between 1980 and 1991, the prevalence of anemia among United States infants and children through 5 years of age declined dramatically, from 7 to