Iron stores of breastfed infants during the first year of life

Area of Science:

• Pediatrics
• Nutritional Science
• Iron Metabolism

Background:

• The initial iron supply at birth, known as the birth iron endowment, is crucial for infant growth.
• Understanding iron status in exclusively breastfed infants is vital, especially under conditions of limited dietary iron intake.

Purpose of the Study:

• To characterize the iron endowment in infants from birth up to 12 months.
• To investigate the relationship between birth iron endowment and the development of iron deficiency in early infancy.
• To assess sex-based differences in iron endowment and iron deficiency risk.

Main Methods:

• Longitudinal study tracking plasma ferritin (PF) and transferrin receptor (TfR) levels from 1 to 12 months in exclusively breastfed infants.
• Infants received Vitamin D supplementation and could have complementary foods from 4 months, excluding formula.
• Iron deficiency was defined as PF < 10 µg/L.

Main Results:

• Birth iron endowment was highly variable, with plasma ferritin levels at 1 month ranging from 38 to 752 µg/L.
• Plasma ferritin declined and stabilized by 5.5 months, while TfR increased with age, inversely correlating with PF.
• Iron deficiency emerged by 4 months, increasing in frequency until 9 months, particularly in infants born with a low iron endowment. Males exhibited lower iron endowment than females, except at 12 months.

Conclusions:

• The size of the birth iron endowment is a significant determinant of iron status in early infancy.
• A small birth iron endowment places infants at high risk for developing iron deficiency before six months of age.
• Male infants are at a greater risk for iron deficiency compared to female infants due to inherently smaller iron endowments.