Their findings reveal that vitamin A deficiency was related to low Hb concentration and plasma ferritin concentration.15 Despite the distinct improvement in iron and vitamin A status, supplementation with vitamin A either did not improve or only marginally improved Hb and iron stores above those achieved with iron supplementation alone.9 Alongside iron, calcium, and folate, vitamin A was also seen as a problem nutrient in the study by Oy et al.14 The gene discussed is GSTM1; the disease is vitamin A deficiency.