Iron is a mineral that supports oxygen transport in the blood and neurological development. For infants, whose brains and bodies are growing rapidly, obtaining enough iron is important. Milk is the primary source of nourishment for infants in their early months, making its iron content a key consideration. The amount and type of iron in milk can vary, influencing how it meets a baby’s needs.
Iron Content Across Milk Types
The concentration of iron differs substantially among human milk, cow’s milk, and infant formula. Human milk contains a low amount of iron, ranging from 0.2 to 0.5 milligrams per liter (mg/L). This level remains fairly constant and is not significantly impacted by the mother’s dietary iron intake, unless she is severely anemic.
In contrast, infant formulas are fortified with iron to much higher levels. Standard iron-fortified formulas in the United States contain between 10 and 12 mg/L of iron. Unmodified cow’s milk, which is not recommended for infants under one year, has very little iron, and what it does contain is not easily used by the infant’s system.
Bioavailability and Absorption of Iron from Milk
The quantity of iron in milk does not provide a complete picture; bioavailability—how much of a nutrient can be absorbed and used by the body—is also a factor. Despite its low iron concentration, the iron in breast milk is highly bioavailable, with infants absorbing as much as 50% of it. This high absorption rate is largely attributed to a protein called lactoferrin, which binds to iron and facilitates its uptake in the infant’s gut.
The iron in cow’s milk and cow’s milk-based formulas has a much lower absorption rate, estimated to be between 7% and 12% for formula. This is partly due to the high concentrations of calcium and certain proteins, like casein, which can interfere with and limit iron absorption. To compensate for this poor bioavailability, formulas are fortified with significantly more iron than what is naturally present in human milk.
Meeting Infant Iron Needs Through Milk
A healthy, full-term baby is born with iron stores inherited from their mother during pregnancy, which are sufficient to meet their needs for approximately the first six months of life. During this period, the highly absorbable iron from breast milk effectively complements these internal reserves. For infants who are not breastfed, iron-fortified formula is designed to provide the necessary amount of iron to support their growth.
After about six months, an infant’s iron needs increase substantially, rising to a recommended 11 mg per day for babies aged 7 to 12 months. At this stage, their birth stores have been depleted, and breast milk alone may no longer be sufficient to meet these higher demands. This is why it is recommended to introduce iron-rich solid foods, such as fortified cereals and pureed meats, around six months of age for all infants, whether breastfed or formula-fed.
Iron Fortification and Dietary Considerations
The practice of fortifying infant formula with iron began as a public health measure to combat iron deficiency, a condition that can affect cognitive and physical development. The American Academy of Pediatrics has recommended iron-fortified formula for infants who are not breastfed since 1969. These formulas ensure that babies receive adequate iron, even with the lower absorption rates associated with cow’s milk protein.
Iron-fortified infant cereals are a common first food designed to meet this need. Other beneficial foods include:
- Pureed meats
- Poultry
- Beans
- Lentils
Pairing these foods with sources of vitamin C, such as fruits and vegetables, can enhance the absorption of non-heme iron found in plant-based foods and fortified products. For the infant, a combination of their initial iron stores, milk, and eventually iron-rich complementary foods works together to support healthy development.