The fourth study by Dillon et al, an RCT measuring the effects of supplementing vitamin A or vitamin B2, in addition to iron, on Hb and serum ferritin (SF) levels, showed an increase in Hb concentration after 8 weeks of iron supplementation with or without vitamin B2 or vitamin A. This implies that anemia in this population was likely to have been due, at least in part, to ID.9 The prevalence of anemia and IDA at baseline was 100% and 56%, respectively. This evidence concerns the gene GSTM1 and anemia (phenotype).