Iron status of one-year-olds and association with breast milk, cow's milk or formula in late infancy

Studies on iron status in infancy and early childhood have shown contradicting results concerning prolonged breast-feeding and cow's milk intake. The aim of the present study was to investigate associations between iron status among one-year-olds and feeding, with focus on the type of milk. Randomly selected healthy infants were prospectively investigated until 1 year of age in two cohorts born 1995-1996 (n = 114) and 2005 (n = 140). Information on birth data, feeding and growth until 12 months and iron status at 12 months was collected. Data from the two cohorts were pooled and the infants categorized into three groups according to their predominant milk consumption at 9 months of age, that is, breast milk, cow's milk or follow-on formula. The prevalence of iron deficiency was highest in the cow's milk group and lowest in the follow-on formula group. According to a linear model, adjusted for gender, birth weight and exclusive breast-feeding duration, cow's milk consumption was negatively associated with serum ferritin (SF) and formula positively, but breast milk not. Predicted SF (mu g/l) = 11.652(intercept) - 5.362(boy) + 0.005 x birth weight (g) + 2.826(exclusively breastfed a parts per thousand yen 4 months) + 0.027 x formula (ml) - 0.022 x cow's milk (ml) + 0.005 x breast milk (ml). Correction for other dietary factors did not change these results. In this pooled analysis, cow's milk intake in late infancy associated negatively, and follow-on formula positively, with iron status. Prolonged partial breast-feeding does not seem to be of importance for iron status. Fortified food seems to improve iron status in late infancy.