The science behind Iron: a key nutrient for early growth and development

Iron is a nutrient that is consistently referred to in the context of early life nutrition. What makes iron so important during this early phase of life, and what roles does it play in the body? Let’s explore the benefits of iron: 

What is iron and why is it so important?

Iron is a mineral found in every living organism. It is an essential element that plays an integral role in human development and metabolism. 

Iron - with atomic number 26 and the symbol “Fe” in the periodic table of elements¹ - is a structural component of many enzymes that are involved in a wide range of metabolic activities. It is critical for the immune and central nervous systems.²,³ Iron also plays an essential role in DNA stability by working as a cofactor to the substances that regulate DNA synthesis and repair; these substances require iron to function, which means our bodies rely on iron for healthy cell development.⁴,⁵

Iron supports our skeletal and digestive systems as well, through its involvement in the creation of collagen and bile acids. Collagen is a significant component of our bones, tendons, cartilage, skin, and muscles.⁶ Bile acids help with breaking down food in our GI tract and the absorption of fats and fat-soluble vitamins; they also assist with getting rid of waste products.⁷ 

Iron stores and shuttles oxygen around the body

Oxygen is carried throughout the body by hemoglobin, a protein in red blood cells. The majority of iron in the body is bound to hemoglobin. There, it plays a critical role in powering hemoglobin to transport oxygen. Without enough iron, tissues and organs won’t get the oxygen they need.¹,⁸

Iron is also stored in muscle cells called myoglobin. Myoglobin stores iron in muscles, and releases it for use in the muscle when needed - this includes the heart muscle!⁹

Why is iron so important for my baby?

There are stages of life when adequate iron is particularly important. These stages coincide with times of rapid development, when iron requirements increase to support faster rates of growth. Two of those times are during toddlerhood and adolescence, and the third is - unsurprisingly - during infancy.¹⁰,¹¹

Adequate iron early in life is essential to support the development of the brain, nervous system, and immune system. Iron also plays a central role in energy metabolism (remember its role as oxygen transporter?). If iron intake is inadequate during this critical period, negative outcomes such as developmental delays and cognitive deficits can result, which are often irreversible.²,¹² Iron deficiency during this early sensitive period of brain development has also been associated with reduced learning ability, effects of which can be seen into adulthood.²,¹⁰⁻¹²

The brain is an organ that is built in stages, and the success of each stage of building depends on the solid building of the previous stage. Imagine a construction project, where scaffolding supports a building structure while new components are added. While the brain is being built - which occurs over the first few years of life - iron plays a prominent role in this so-called scaffolding process.¹⁰

Is there such a thing as too much iron?

Iron is a highly regulated mineral, and having just the right amount - not too little, but also not too much - is critical. While much of the focus around iron intake for infants and young children is making sure they don’t get too little of it, the reality is that too much iron also has negative consequences. Excess iron can be associated with poor growth, undesired changes to the gut microbiota, increased inflammation, and decreased absorption of other nutrients like zinc and copper.¹³ It’s important to get just the right amount of iron throughout all stages of life and especially during infancy. 

Recommended intakes of iron in the US and Europe  

The Recommended Dietary Allowance (RDA) for iron during the first six months of life is 0.27 mg/day. It’s important to note that this is based on the iron level in breastmilk, where it’s present in a form that is highly efficiently absorbed. For infants 6 to 12 months of age, the RDA for iron is 11 mg/day.¹⁴

Infants are born with iron stores, yet these start to decline around four months of age and generally are depleted by six months of age.² The American Academy of Pediatrics recommends that exclusively or partially breastfed infants should be started on an iron supplement that provides 1 mg of iron per day around four months of age.¹⁴ There are many iron supplements for babies available over-the-counter, but it's always a good idea to discuss any supplement use with your pediatrician. 

For infants who are exclusively formula-fed, as long as they’re consuming an infant formula that meets FDA and other expert guidelines for iron in infant formula, a supplemental source of iron is not needed. Standard FDA-regulated US infant formulas can meet the iron needs of exclusively formula-fed infants for the first year of life.¹⁵

European recommendations for iron intake vary compared to those of the US. The European Society of Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) does not recommend routine iron supplementation for healthy, full-term infants. They do state, however, that the iron content of iron-fortified infant formula should be 4 to 8 mg/L.¹⁶

The regulatory requirements for iron infant formula also differ somewhat between the US and Europe. The regulations are illustrated in the figure below. 

Are there low-iron infant formulas? 

The American Academy of Pediatrics makes clear recommendations on the amount of iron that infant formulas should be supplemented with: 4.0-12.0 mg per liter. They recommend that formulas with lower levels of iron be discontinued, but state that if companies continue to manufacture these low-iron formulas, they should be labeled as “nutritionally incomplete” as they place infants at risk for iron deficiency anemia.¹⁷ Additionally, the US FDA requires infant formulas with less than 1 mg of iron per 100 kcal include a label statement that “additional iron may be necessary.”¹⁵ Baby formula without any iron at all would not be approved for use by the US FDA - these products may exist in other countries, but are inappropriate for routine use. 

Iron in Bobbie Baby Formula

Bobbie organic infant formula has 1.2 mg of iron per 100 kcal and meets both the US and EU regulatory requirements for iron in infant formula. Like all U.S. infant formulas, the amount of iron in Bobbie is aligned with the recommendations outlined in the US Infant Formula Act for iron concentration in infant formula. The iron source in Bobbie infant formula is ferrous sulfate.

Key take-away

Iron gets a lot of attention in the world of infant nutrition for good reason. It plays many critical roles in overall growth and development. Having just the right amount - not too little and not too much - during sensitive periods of development will help support brain health and development, the immune system, the skeletal system, and even the GI tract. To talk about iron with your patients, you can use this iron infographic


¹Periodic Table of Elements - PubChem 

²Abbaspour N, Hurrell R, Kelishadi R. Review on iron and its importance for human health. J Res Med Sci. 2014 Feb;19(2):164-74. PMID: 24778671; PMCID: PMC3999603.

³Eussen S, Alles M, Uijterschout L, Brus F, van der Horst-Graat J. Iron intake and status of children aged 6-36 months in Europe: a systematic review. Ann Nutr Metab. 2015;66(2-3):80-92. doi: 10.1159/000371357. Epub 2015 Jan 21. PMID: 25612840.

⁴Puig S, Ramos-Alonso L, Romero AM, Martínez-Pastor MT. The elemental role of iron in DNA synthesis and repair. Metallomics. 2017 Nov 15;9(11):1483-1500. doi: 10.1039/c7mt00116a. PMID: 28879348.

⁵Zhang C. Essential functions of iron-requiring proteins in DNA replication, repair and cell cycle control. Protein Cell. 2014;5(10):750-760. doi:10.1007/s13238-014-0083-7

Collagen | The Nutrition Source | Harvard TH Chan School of Public Health

Bile Salts in Your Body: Function, Benefits, and More 

⁸Aisen P, Enns C, Wessling-Resnick M. Chemistry and biology of eukaryotic iron metabolism. Int J Biochem Cell Biol. 2001 Oct;33(10):940-59. doi: 10.1016/s1357-2725(01)00063-2. PMID: 11470229.

Myoglobin: What It Is, Function, Test & Results 

¹⁰Georgieff MK. Iron assessment to protect the developing brain. Am J Clin Nutr. 2017;106(Suppl 6):1588s-1593s.

¹¹Georgieff MK. The role of iron in neurodevelopment: fetal iron deficiency and the developing hippocampus. Biochem Soc Trans. 2008;36(Pt 6):1267-1271. doi:10.1042/BST0361267

¹²Domellöf M. Iron requirements in infancy. Ann Nutr Metab. 2011;59(1):59-63. 

¹³Lönnerdal B. Excess iron intake as a factor in growth, infections, and development of infants and young children. Am J Clin Nutr. 2017;106(Suppl 6):1681s-1687s.

¹⁴Baker RD, Greer FR. Diagnosis and prevention of iron deficiency and iron-deficiency anemia in infants and young children (0-3 years of age). Pediatrics. 2010;126(5):1040-1050.  

¹⁵United States Food and Drug Administration. Code of Federal Regulations - Part 107, Infant Formula. Published 2022. Updated Jan 6, 2022. Accessed June 13, 2022.

¹⁶Domellöf M, Braegger C, Campoy C, Colomb V, Decsi T, Fewtrell M, Hojsak I, Mihatsch W, Molgaard C, Shamir R, Turck D, van Goudoever J; ESPGHAN Committee on Nutrition. Iron requirements of infants and toddlers. J Pediatr Gastroenterol Nutr. 2014 Jan;58(1):119-29. doi: 10.1097/MPG.0000000000000206. PMID: 24135983.

¹⁷Iron fortification of infant formulas. American Academy of Pediatrics. Committee on Nutrition. Pediatrics. 1999 Jul;104(1 Pt 1):119-23. PMID: 10390274. 

The content on this site is for informational purposes only and not intended to be a substitute for professional medical advice, diagnosis or treatment. Discuss any health or feeding concerns with your infant’s pediatrician. Never disregard professional medical advice or delay it based on the content on this page.