GSTM1 and anemia: According to the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) [7,8], iron deficiency constitutes 40%–50% of anemia cases (iron-deficiency anemia defined as a Hb concentration of less than or equal to 10.0 g/dL) in older children and up to 80% in preschool children (2–5 years).