What is iron?
Iron is an essential mineral that plays a critical role in human health and well-being, and is responsible for carrying oxygen from the lungs to the rest of the body, fortifying the immune system and helping cells to produce energy.
There are two main forms of iron found in the diet:
- Heme iron, which is found in animal-based foods such as meat and poultry,
- Non-Heme iron, which is found in plant-based foods such as leafy greens, beans, and iron-fortified foods.
Heme iron is more easily absorbed by the body than non-heme iron, but both forms are important for maintaining good health and preventing Iron-deficiency anaemia (IDA), a condition where the body does not have enough red blood cells due to a lack of iron. This is the most common nutritional deficiency in the world and can cause fatigue, weakness, and decreased ability to concentrate.
UK and USA Iron recommendations
The recommended daily allowance (RDA) of iron for infants, children, and adults varies between the UK and the USA, primarily due to the variations in dietary patterns and cultural practices between the two countries.
For infant formula USA regulations require baby formulas to contain at least 1mg of iron per 100kcal, whereas European guidelines require at least 0.3mg per 100kcal. This is because all USA formulas are required to be nutritionally complete for babies ages 0 to 12 months, whereas British (and European) formulas have varying nutrient levels based on the stage for which the formula is designed.
“From 6-12 months recommendations for iron increases to meet the increased demands of the body; with the USA at 11mg per day and Europe at 7.8mg per day.”
The higher recommended iron intake in the USA is based on research suggesting that a significant number of infants in the country are at risk of iron deficiency due to low iron intake and limited access to iron-rich foods.
In contrast, research also suggests that a lower recommended iron intake is adequate for most healthy infants and may even be beneficial to their health by supporting natural adaptive strategies that can help prevent illness in young infants. However, some infants, particularly those born prematurely or with low birth weights, may require higher iron intakes to meet their developmental needs.
Iron and pregnancy
During pregnancy, iron is needed to support the growth of the foetus and to ensure that the mother has adequate stores of iron to meet the increased blood volume and oxygen demand of pregnancy.
It is common for pregnant women to experience a decline in iron levels, which is why it is essential to monitor their iron levels throughout pregnancy. IDA in pregnancy can cause fatigue, shortness of breath, and a higher risk of preterm delivery or low birth weight.
“Pregnant women are particularly at risk for IDA with the increased demand on their bodies for essential nutrients.”
To ensure adequate iron intake during pregnancy, it is recommended that women are advised to continue to consume around 30mg of iron per day (more if advised by their healthcare practitioner) and to pay attention to symptoms suggestive of low iron levels.
Iron and infant feeding
Babies are born with iron stored in their bodies that they built up from their mother in utero, and they continue to get iron from either breastmilk or iron-fortified infant formula. Although the iron content in breastmilk is lower than that in infant formula, the absorption rate in breastfed infants is considerably higher.
The iron content of human milk is 0.5 mg/L compared with 10 to 12 mg/L in supplemented cow-milk formulas. Breastfed infants absorb up to 50% of consumed iron, compared with a 7-12% absorption rate for formula-fed infants which is due to the high bioavailability of lactoferrin in human milk. The risk of iron deficiency increases after 4 months of age since most full-term infants are born with adequate iron stores to support haemoglobin synthesis through the first 4-6 months after birth.
“Formula-fed infants up to 6 months of age should receive iron-fortified infant formula, with an iron content of 4 to 8 mg/L”
When babies do not get enough iron, they can also develop IDA. In infants IDA can present itself as pale skin, irritability, poor feeding and lethargy. In severe cases, IDA can affect a baby’s cognitive and behavioural development by causing changes in neurotransmitter homeostasis, decreased myelin production, impaired synaptogenesis, and a decline the function of the basal ganglia – therefore it is essential to address any iron deficiencies early on.
Levels below the paediatric haemoglobin concentrations set by the WHO indicate anaemia;
- 6 months–4 years: 110g/l.
- 5-11 years: 115g/l.
- 12-14 years: 120g/l.
IDA is diagnosed via a full blood count (FBC) and ferritin level. The FBC includes the number and type of blood cells in addition to the haemoglobin level and can be used to diagnose anaemia, while the ferritin level reflects iron stores.
Iron and weaning
Between 4 and 6 months of age the iron stored from pregnancy is at a low level, in addition their bodies now require more iron for the rapid growth they are going through. It is also the time they are ready to start eating (and getting iron from) solid food.
The weaning process is an ideal time for parents to build their child’s iron supplies from sources like iron-fortified cereals, meat, poultry, and fish. Vegetarian families will need to look to iron-rich foods like tofu, beans, lentils, and iron-fortified cereals as a source of iron.
It is important to note that the absorption of iron differs between animal-based and plant-based sources. Heme iron, which is present in meat, is absorbed twice as efficiently by the body compared to non-heme iron, which is found in plant-based sources or fortified foods., and parents should be advised accordingly based on their diet choices.
- Mothers, during their pregnancy, play a vital role in preventing their baby from developing iron deficiencies in the early weeks and months of life, pointing to an increased importance in a balanced diet and vigilance of IDA symptoms.
- Breastmilk provides everything infants need in early life and whilst iron levels are lower in breastmilk, it is also more easily absorbed due its bioavailability, hence the fortification of infant milk formulas.
- Infant formula manufacturers ensure that recipes are fortified with enough iron to meet babies growing needs, although minimum requirements do vary by region.
- In the UK all standard formulas should contain a min of 0.3mg and a maximum of 1.3kcal per 100kcal, and in the US the FDA require a minimum of 1mg/100ckal.
- Weaning provides a great opportunity to introduce babies to a variety of iron rich foods to replenish possibly depleted iron stores and prevent IDA.
- Healthcare practitioners should assess the individual dietary habits of families to make specific recommendations on iron requirements.
WHO. Iron Deficiency Anaemia: Assessment, Prevention and Control. Geneva: WHO; 2001.
Institute of Medicine (US) Committee on the Evaluation of the Addition of Ingredients New to Infant Formula. Infant Formula: Evaluating the Safety of New Ingredients. Washington (DC): National Academies Press (US); 2004. Executive Summary. Available from: https://www.ncbi.nlm.nih.gov/books/NBK215845/
Figueiredo ACMG, Gomes-Filho IS, Silva RB, Pereira PPS, Mata FAFD, Lyrio AO, Souza ES, Cruz SS, Pereira MG. Maternal Anemia and Low Birth Weight: A Systematic Review and Meta-Analysis. Nutrients. 2018 May 12;10(5):601. doi: 10.3390/nu10050601. PMID: 29757207; PMCID: PMC5986481.
Institute of Medicine (US) Committee on the Evaluation of the Addition of Ingredients New to Infant Formula. Infant Formula: Evaluating the Safety of New Ingredients. Washington (DC): National Academies Press (US); 2004. 2, Defining Safety for Infants.
Institute of Medicine (US) Committee on the Evaluation of the Addition of Ingredients New to Infant Formula. Infant Formula: Evaluating the Safety of New Ingredients. Washington (DC): National Academies Press (US); 2004. 3, Comparing Infant Formulas with Human Milk.
Quinn EA. Too much of a good thing: evolutionary perspectives on infant formula fortification in the United States and its effects on infant health. Am J Hum Biol. 2014 Jan-Feb;26(1):10-7. doi: 10.1002/ajhb.22476. Epub 2013 Oct 21. PMID: 24142500.
Jane M. Brotanek, Jacqueline Gosz, Michael Weitzman, Glenn Flores; Iron Deficiency in Early Childhood in the United States: Risk Factors and Racial/Ethnic Disparities. PediatricsSeptember 2007; 120 (3): 568–575. 10.1542/peds.2007-0572
Carter RC, Jacobson JL, Burden MJ, Armony-Sivan R, Dodge NC, Angelilli ML, Lozoff B, Jacobson SW. Iron deficiency anemia and cognitive function in infancy. Pediatrics. 2010 Aug;126(2):e427-34. doi: 10.1542/peds.2009-2097. Epub 2010 Jul 26. PMID: 20660551; PMCID: PMC3235644.
Pivina L, Semenova Y, Doşa MD, Dauletyarova M, Bjørklund G. Iron Deficiency, Cognitive Functions, and Neurobehavioral Disorders in Children. J Mol Neurosci. 2019 May;68(1):1-10. doi: 10.1007/s12031-019-01276-1. Epub 2019 Feb 18. PMID: 30778834.