Growth and intakes of energy and zinc in infants fed human milk

Abstract

The objectives of this study were to examine the growth pattern of healthy infants who were fed human milk exclusively for > or = 5 months and its relationship to intakes of milk, energy, and zinc. Monthly anthropometric measurements were obtained on 71 infants through 7 months of age and on 43 through 9 months. Milk zinc concentrations were determined and milk intake was measured by 3-day test weighing. Mean (+/- SD) calculated energy intake from human milk was 106 +/- 20, 79 +/- 11, 70 +/- 10, and 57 +/- 12 kcal/kg per day at 2 weeks and 3, 5, and 7 months of age, respectively; intake from milk plus solids was 70 +/- 13 kcal/kg at 7 months. Zinc intakes from human milk were 2.3 +/- 0.68, 1.0 +/- 0.43, 0.81 +/- 0.42, and 0.52 +/- 0.31 mg/day at these points. The maximum mean weight-for-age percentile for both sexes was 62 at 2 months; the mean percentile declined to 33 by 7 months and to 25 by 9 months of age. Mean length-for-age percentile declined from 43 at 2 weeks of age to 28 and 26 by 7 and 9 months of age, respectively. Energy intake at 2 weeks of age was positively associated with the weight increment from 2 weeks to 7 months of age (p = 0.003) and with a change in weight-for-age z scores from 2 weeks to 3 months of age (p = 0.028). Mean energy intakes of healthy breast-fed infants are lower through the first 7 months of life than current recommendations. Zinc intakes of breast-fed infants are likely to be adequate, on average, through 5 months of breast-feeding but subsequently are marginal without the introduction of weaning foods. Revision of standards for growth based on observations in breast-fed infants may be appropriate, but the possibility of growth-limiting nutrient deficiencies should also be investigated.