GSTM1 and anemia: It is worth noting, however, that multiple micronutrient supplementation, as compared to iron supplementation alone, appears to have some beneficial effects on Hb concentration.3,4 In terms of vitamin B2 status and anemia, 3 of the studies by Dillon et al are somewhat contradictory, since they found that vitamin B2 was positively associated with Hb concentration and plasma ferritin in one study, but not the other 2.