iron absorption

The body’s ability to regulate iron is essential to its function. A new study explores the difference in iron absorption between infants and adults.

Sources of iron for infants are found in iron stores within the liver and hemoglobin concentrations. Dietary intake of iron is minimal in an infant’s diet, with only small amounts available in breast milk. While iron stores in the body are sufficient for infants, preterm infants or infants born with low birth weights have lower iron stores at birth coupled with greater weight gain over time. As a solution, iron supplementation is required for preterm or low-birth-weight infants prior to six months of age. Maternal iron deficiency anemia lowers iron stores in the infant as well. During the birthing process, the time at which the umbilical cord is clamped also affects iron stores in the infant.

An American study published in the American Journal of Clinical Nutrition summarizes iron absorption, the effects of iron, and the mechanism of iron homeostasis in infants. For the study, researchers extrapolated data from two clinical trials conducted in Sweden. In the clinical trials, researchers fed a group of infants with formulas varying in iron concentrations of 4mg/L, 2mg/L, and 1.6mg/L. Another group of infants were exclusively breastfed. The infants were six months of age or younger

The study showed that the infants fed with low iron-containing formulas did not experience any significant iron deficiency at six months of age. The results suggested that dietary iron has little impact on the risk of iron deficiency in infants below six months old. The bioavailability of iron also has an impact on the body’s ability to absorb copper and zinc. Infants who consumed a formula with a higher iron concentration had relatively lower concentrations of copper than infants fed with a low iron-containing formula.

Regulation of iron absorption involves hormones, iron transporters, and transcription factors. The study explained that the expression of an iron transporter found in the intestine is regulated by an iron-regulatory protein. To test the mechanism of iron homeostasis at different ages, the researchers utilized young rats as experimental subjects. They found that the high iron absorption at a young age was attributed to the wide expression of an iron transporter in the intestine. In adults, iron absorption occurred majorly in the duodenum. The study concluded that regulation of iron transporters is absent at an early age.

The research confirmed that iron absorption in infants differs significantly from the iron absorption mechanism in adults. The information is valuable for medical professionals when assessing iron needs of an individual with respect to their age. Dieticians can personalize nutritional plans for infants accordingly. With further research, treatments and dietary plans for those with iron deficiency may become increasingly efficient through targeting of specific iron transporters to ensure adequate iron absorption.

Written by Shrishti Ahuja, HBSc

Reference: Lönnerdal, B. (2017). Development of iron homeostasis in infants and young children. The American Journal of Clinical Nutrition. doi:10.3945/ajcn.117.155820

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