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Iron Balance and Iron Nutritional Status in Preterm Infants During the First Four Months of Life
Richard J Cooke1, Ian Griffin2
1The University of Tennessee Health Science Center, Memphis, TN.
Insights
Iron absorption in preterm infants is not dose-dependent or related to iron stores. Absorption increases only when iron delivery to tissues decreases, meeting the needs of rapidly growing infants.
Area of Science:
- Neonatal Nutrition
- Pediatric Gastroenterology
- Iron Metabolism
Background:
- Preterm infants have unique nutritional needs due to rapid growth and immature systems.
- Iron is crucial for development, but absorption mechanisms in this population require further understanding.
Purpose of the Study:
- To investigate if iron absorption in preterm infants is dose-dependent.
- To determine if iron absorption is influenced by the infant's iron nutritional status (INS).
Main Methods:
- 18 preterm very-low-birth-weight infants (VLBWI) were studied.
- Three 48-hour balance studies were conducted per infant.
- Iron nutritional status was assessed via hemoglobin, MCV, hematocrit, ferritin, transferrin, and transferrin saturation.
Main Results:
- No correlation was found between iron intake and absorption.
- Net and percentage iron absorption increased over time (P < 0.01).
- Transferrin saturation, MCV, and hematocrit explained 67% of the variation in iron absorption (P < 0.001).
Conclusions:
- Iron absorption in preterm infants is not dose-dependent.
- Absorption increases when iron delivery to tissues is low, indicating a regulatory mechanism to meet growth demands.
- Iron nutritional status, particularly transferrin saturation, MCV, and hematocrit, significantly influences iron absorption.
Objectives:
To determine whether iron absorption occurs in a dose-dependent fashion and/or is a function of iron nutritional status (INS) in preterm infants during the first 4 months of life.
Methods:
Preterm very-low-birth-weight infants (VLBWI) were fed an iron-fortified (0.7 mg/dL) infant formula. Three 48 h balance studies were performed on each infant. INS was determined by serially measuring hemoglobin, mean corpuscular volume (MCV), hematocrit, ferritin, transferrin and transferrin saturation levels. The data were analyzed using ANOVA and stepwise regression.
Results:
Fifty-four balance studies were performed in 18 infants (birth weight, 1347 ± 201 g; gestation, 30 ± 1.3 weeks; mean ± standard deviation) at 33 ± 1.3, 34 ± 1.2, and 48 ± 0.5 weeks corrected age and weights of 1768 ± 260, 2298 ± 314, 5127 ± 939 g. No relationship was detected between iron intake and absorption. Intake decreased during the study (1.17 ± .08, 1.24 ± 0.11 > 1.1 ± 0.15 mg · kg-1 · day-1) but net (0.32 ± 0.26, 0.36 ± 31 < 0.49 ± .23 mg · kg-1 · day-1) and % (27 ± 22, 29 ± 23 < 46 ± 21) absorption increased (P < 0.01). Serum ferritin, transferrin saturation and MCV fell, while hematocrit and hemoglobin remained stable. No relationship was noted between serum ferritin and iron absorption but transferrin saturation (54%), MCV (7%), and hematocrit (6%) accounted for 67% of the variation in iron absorption (P < 0.001).
Conclusions:
At intakes of 0.8-1.4 mg · kg-1 · day-1, iron absorption is not dose-dependent nor affected by iron stores. Only when iron delivery to the tissues decreases does absorption increase to meet needs in these otherwise normal and rapidly growing infants.
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