Breastfed infants are at risk for iron deficiency anemia and also deficiencies of what other nutrient?

Breastfed infants are at significant risk for vitamin D deficiency in addition to iron deficiency anemia. Human breast milk contains very little vitamin D — typically less than 25 IU per liter — which is far below the 400 IU per day recommended for infants. Vitamin D is critical for calcium absorption and proper bone mineralization; deficiency can lead to rickets. Because most infants have limited sun exposure, especially in northern latitudes or when kept indoors, cutaneous synthesis of vitamin D is often inadequate. The American Academy of Pediatrics recommends supplementing all breastfed infants with 400 IU of vitamin D daily beginning within the first few days of life. Iron deficiency risk arises because breast milk, while highly bioavailable, contains limited iron, and infants' prenatal iron stores become depleted around four to six months of age. Vitamin C is generally adequate in breast milk if the mother's diet is sufficient, and breastfed infants are not routinely at elevated risk for vitamin C deficiency. Calcium, while present in breast milk in smaller absolute amounts than formula, is highly bioavailable, so deficiency is not a primary concern for breastfed infants. Vitamin E is found in breast milk at levels that are generally adequate for infant needs. Vitamin D supplementation for breastfed infants is therefore a standard clinical recommendation.