Iron status at 12 months of age - effects of body size, growth and diet in a population with high birth weight

Objective: To investigate effects of growth and food intake in infancy on iron status at the age of 12 months in a population with high birth weight and high frequency of breast-feeding. Design: In a longitudinal observational study infants' consumption and growth were recorded. Weighed 2 day food records at the ages of 6, 9 and 12 months were used to analyse food and nutrient intake. Setting: Healthy-born participants were recruited from four maternity wards. Blood samples and growth data were collected from healthcare centres and food consumption data at home. Subjects: Newborn infants (n=180) were selected randomly according to the mother's domicile and 77% (n=138) participated, of them, 83% (n = 114), or 63% of original sample, came in for blood sampling. Results: Every fifth child was iron-deficient (serum ferritin < 12 mug/l and mean corpuscular volume < 74fl) and 2.7% were also anaemic (Hb < 105 g/l). Higher weight gain from 0 to 12 months was seen in infants who were iron-deficient at 12 months (6.7 +/- 0.9kg) than in non-iron-deficient infants (6.2 +/- 0.9kg) (P = 0.050). Serum transferrin receptors at 12 months were positively associated with length gain from 0 to 12 months (adjusted r(2) = 0.14; P = 0.045) and mean corpuscular volume negatively to ponderal index at birth (adjusted r(2) = 0.14; P = 0.019) and 12 months (adjusted r(2) = 0.17; P = 0.006). Iron-deficient infants had shorter breast-feeding duration (5.3 +/- 2.2 months) than non-iron-deficient(7.9 +/- 3.2 months; P = 0.001). Iron status indices were negatively associated with cow's milk consumption at 9-12 months, significant above 460g/day, but were positively associated with iron-fortified breakfast cereals, fish and meat consumption. Conclusions: In a population of high birth weight, iron deficiency at 12 months is associated with faster growth and shorter breast-feeding duration from 0 to 12 months of age. The results suggest that a diet of 9-12-month-olds should avoid cow's milk above 500g/day and include fish, meat and iron-fortified breakfast cereals to improve iron status. Sponsorship: The Icelandic Research Council, Research Fund of the University of Iceland.