How Iron Status Affects Iron Absorption in Infants
Nutrition is complex, especially in the realm of bioavailability. For nutrients with known deficiency disease, such as iron, assessing the effect of an intervention is more complicated than a simple dose-response effect. Iron absorption depends on the type of iron that is provided in the food or supplement (particularly heme vs. non-heme iron), the levels of iron absorption promotors such as vitamin C in the meal, the levels of iron absorption inhibitors such as phytate or tannic acid, and the health and iron status of the individual. This is particularly important because nutritional anemia, caused predominantly by iron deficiency, is a significant worldwide problem and the most common nutritional deficiency (according to the World Health Organisation) that roughly 1.6 billion people suffer from. In particular, women of child-bearing age (especially pregnant women), infants and toddlers are most affected.
Finkelstein and colleagues investigated the role of prenatal iron and iron absorption in a group of 59 breastfed infants aged two and five months. The infants lived in a semi-urban area in Lima, Peru. Infants were divided into two groups based on provision of iron to their mothers during pregnancy: those that received regular supplemental iron during pregnancy, and those that did not. The iron absorbance using 58Fe iron isotopes in the infants was determined at both 2 and 5 months of age, as were a number of important measures of iron status in both the mothers and infants at both time periods.
At the baseline measurement when infants were aged around 2 months, almost two thirds of the women were anemic, as were three quarters of the infants. At this time point, iron deficiency anemia was found in 37% of the mothers and 2 months, and this was reduced to only 21% at 5 months, presumably as these breastfeeding women recovered from the iron demands of pregnancy. No infants had iron deficiency anemia at 2 months, however 25% had developed the condition by the age of 5 months. Infants of mothers that were iron deficient at 2 months were much more likely to be iron deficient at 5 months than the offspring of non-deficient mothers.
There was a slight decrease in the iron concentration in breast milk between measurements taken at 2 and 5 months, although it was not statistically significant. The iron absorption in the infants increased significantly between 2 and 5 months; it is well known that iron uptake increases in people who have low iron stores (see open access review from Finberg). This also appears to be the case in infants.
Although parents are advised that infant iron stores at birth are enough to last through the first 6 months of life, the data from this study show that iron stores were depleted in a quarter of infants by 5 months, in this Peruvian population. A high proportion of postpartum women were also iron depleted. Although low maternal iron status appears to be associated with increased risk of iron deficiency by 5 months of age in infants, presumably due to a better iron status and transfer during pregnancy, increases in supplemental iron did not have an effect. Information about iron supplementation was observational, however, and other factors may have affected infant iron levels.
Vulnerable populations like infants and postpartum women appear to be at risk of iron deficiency in Peru. The prevalence of iron deficiency was much higher in this population compared to in well-nourished populations. Interventions that improve the iron status of people living in developing countries are urgently needed to improve the health of infants and their mothers.
Julia L Finkelstein, Kimberly O O'Brien, Steven A Abrams, and Nelly Zavaleta. Infant iron status affects iron absorption in Peruvian breastfed infants at 2 and 5 mo of age. Am J Clin Nutr 2013 ajcn.056945; First published online October 2, 2013. doi:10.3945/ajcn.112.056945
Finberg KE. Unraveling mechanisms regulating systemic iron homeostasis. Hematology Am Soc Hematol Educ Program. 2011;2011:532-7. doi: 10.1182/asheducation-2011.1.532. http://www.ncbi.nlm.nih.gov/pubmed/22160085
Kraemer K. Nutritional Anemia. 2007. Sight and Life Press, Basel, Switzerland. http://www.sightandlife.org/fileadmin/data/Books/Nutritional_anemia_book.pdf