To examine if other nutrients (RBC folate, serum retinol, or vitamin B12) were associated with low Hb concentrations, the prevalence of anemia was examined in those whose SF ≥ 15 μg/dL (not ID), but whose RBC folate and vitamins A and B12 levels were above or below the established cutoffs. This evidence concerns the gene GSTM1 and anemia (phenotype).