In a study by Kaetelhut et al, iron supplementation on a weekly basis for 5 weeks, regardless of the other nutrients (folic acid, vitamin A, and vitamin C) added to the supplement, led to an improvement in Hb concentrations.3 Nearly 30% of the sample was anemic at baseline, and after supplementation, the anemia rate reduced to 25.6%. Here, GSTM1 is linked to anemia (phenotype).