Albertine Donker

Chapter 2 62 Table 2. Continued B. Iron flows Neonate a Infant b Child c Adolescent d Adult e A. Dietary intake (mg/d) 0.2-0.3 h,I 160,216 10 217 13 147,160,217,218 15-18 147,218,219 10-14 1 B. Non-absorbed dietary iron (mg/day) 0.1 216 9.5 217 12.5 220 10-17 219 8-13.5 1 C. (Dietary) iron absorption (mg/day) f 0.2-0.3 9,157,216 0.5-1.0 217,221 0.5 220 0.8-5.0 197,219 0.5-2.0 1 D. Epithelial iron loss (mg/day) 0.2 214 0.2 214 ? 0.7 219 1-2 1 E. Erythropoietic iron usage 0.2 97,216 ? ? ? 0.4-1.6 1 F. Iron recycling from senescent erythrocytes (mg/day) 2 3 7 18 20-25 1 G. Non-erythropoietic iron usage g 0.1 ? ? ? 0.1-0.4 H. Iron storage ? ? ? ? ? Categorization in the Figure 1 and Table 2 is based on the infancy-childhood-puberty model. 55,56 For each phase a certain age was chosen as an example for iron contents and iron flows. a Based on term neonate, assuming a weight of 3 kg, and a circulating volume of 80-85 mL/kg, hence approximately 240-250 mL 222 b Based on infant aged 1 year, assuming a weight of 10 kg, 53 and a circulating volume of 75-80 mL/kg, hence approximately between 750-800 mL. 223 c Based on child aged 6 years, assuming a weight of 23 kg, 53 and a circulating volume of 70-75 mL/kg, hence approximately between 1500- 1750 mL. 223 d Based on male adolescent, aged 15 years, assuming a weight of 50 kg, 53 and a circulating of volume 65-70 mL/kg, hence approximately between 3250- 3500 mL. 223 e Based on male adult, assuming a weight of 70 kg, and circulating volume of 4000-5000 mL. 1 f Absorption of iron is highly dependent on iron status and composition of diet; iron deficiency and a diet rich of vitamin C and animal protein enhance iron absorption, 217 while iron loading and the existence of calcium and phytates and polyphenols decrease ion absorption. 224 g Non-erythropoietic iron usage for the neonate and adults were calculated by subtracting erythropoietic iron usage (E) from the amount of absorbed iron (D). For the other age groups this deduction was not possible since data on E are lacking. h Based on calculation of breastfed term neonate of 3 kg with an intake of on average 500 mL breast milk per day. Breast milk has a relatively low iron content; colostrum contains approximately 0.8 mg/L iron and the concentration in mature milk declines over time from 0.6 mg/L at 2 weeks to 0.3 mg/l at 5 months postpartum. 174,225 The iron content of formula feeding is on average 4-12 mg/L, which is 7-40 times greater than the iron levels in breast milk in order to compensate for the poorer availability of iron in formula milk compared to breast milk. 8 I Of note, daily iron requirement for a neonate is 0.55-0.75 mg/day, meaning that iron stores are drawn on during breastfeeding. 217 However, after birth, iron stores significantly increase due to the fetal-to- adult hemoglobin switch, i.e. the breakdown of fetal Hb (HbF) that is replaced by adult Hb (HbA) by endogenous erythropoiesis, which typically resumes when Hb has decreased from 17-12 g/dL. 8,2