According to WHO [31], anemia caused by iron deficiency can be classified according to three stages, ranging from the first (mild form) to the third stage (severe anemia) with low Hb (<70 g/L for children under 5 years and pregnant women, and <80 g/L in children over 5 years, adolescents, and adults). Here, GSTM1 is linked to anemia (phenotype).