Iron supplementation is positively associated with increased serum ferritin levels in 9-month-old Danish infants

Fe deficiency is still common in infancy, even in affluent societies, and has prompted Fe fortification of food products and use of Fe supplements in many populations. In the present study, we tested the hypothesis that Fe status among 9-month-old infants following the Danish Fe supplementation recommendation (> 400 ml Fe-fortified formula or 8mg Fe/d) is associated with more favourable levels of Fe status indicators compared to those not following the recommendation. A random sample of 9-month-old infants living in Copenhagen was established and 312 healthy term infants were examined at 9.1 (SD 0.3) months of age. Blood samples were available from 278 infants. Overall, twenty infants (7.8 %) had Fe deficiency (serum ferritin < 12 mu g/l) and < 1% had Fe deficiency anaemia (serum ferritin < 12 mu g/l and Hb < 100 g/l). Serum ferritin was positively associated with birth weight (P < 0.001), intake of fortified formula and follow-on formula (P = 0.001), and female sex (P < 0.001). Cow's milk intake and length of exclusive breast- feeding were negatively associated with Hb levels (P = 0.013 and P < 0.001). Serum ferritin levels were significantly higher (P < 0.0001) and transferrin receptor (TfR) was significantly lower (P = 0.003) among infants (n 188) meeting the Fe supplementation recommendation compared to those (n 67) not meeting the recommendation. No significant difference between these two groups was found for Hb. In conclusion, this study confirmed that Fe status of infants following the Danish Fe supplementation recommendation was significantly associated with increased serum ferritin and decreased levels of TfR indicating more favourable Fe status, compared to infants not following the recommendation.