The World Health Organization (WHO) defines anemia based on age, sex, and pregnancy status; for children aged 6 months to 5 years, anemia is defined as an Hb level below 11.5 g/dL; for adult men, it is defined as an Hb level below 13 g/dL; and for non-pregnant women, it is defined as an Hb level below 11 g/dL (1). This evidence concerns the gene GSTM1 and anemia (phenotype).