The relationship between the severity of iron deficiency anemia and the absorption of iron showed that patients with severe anemia (Hb< 10 g/dL) have an higher increase in serum iron after the OIAT (about nine times) than mild/moderate forms of anemia (TO: 12 μg/dL and 35.76 μg/dL vs. T1 109.2 μg/dL and 104.66 μg/dL in severe anemia and mild/moderate anemia, respectively). This evidence concerns the gene GSTM1 and anemia.