Effect of dietary protein on plasma insulin-like growth factor-1, growth, and body composition in healthy term infants: a randomised, double-blind, controlled trial (Early Protein and Obesity in Childhood (EPOCH) study)

Abstract

The effect of protein intake on growth velocity in infancy may be mediated by insulin-like growth factor-1 (IGF-1). This study aimed to determine the effects of formulae containing 1·8 (F1·8) or 2·7 g (F2·7) protein/418·4 kJ (100 kcal) on IGF-1 concentrations and growth. Healthy term infants were randomly assigned to receive F1·8 (n 74) or F2·7 (n 80) exclusively for the first 4 months of life. A group of breast-fed infants (n 84) was followed-up simultaneously (reference). Growth and body composition were measured at 0·5, 4, 6, 12, 36, 48 and 60 months of life. The IGF-1 concentrations at 4 months (primary outcome) were similar in the F1·8 (67·1 (sd 20·8) ng/l; n 70) and F2·7 (71·2 (sd 27·5) ng/l; n 73) groups (P=0·52). Both formula groups had higher IGF-1 concentrations than the breast-fed group at 4 and 9 months of age (P≤0·0001). During the first 60 months of life, anthropometric parameters in the F1·8 group were lower compared with the F2·7 group, and the differences were significant for head circumference from 2 to 60 months, body weight at 4 and 6 months and length at 9, 12 and 36 months of age. There were no significant differences in body composition between these two groups at any age. We conclude that, in formula-fed infants, although increased protein intake did not affect the IGF-1 concentration during the first 12 months of life, it did affect length and head circumference growth, suggesting that factors other than IGF-1 could play roles in determining growth velocity.

Keywords: AE adverse events; CHOP Childhood Obesity Project Study Group; DEXA dual energy X-ray absorptiometry; Dietary proteins; EPOCH Early Protein and Obesity in Childhood; Fat mass; Growth; IGF-1 insulin-like growth factor-1; IGFBP IGF-binding protein; ITT intention-to-treat; Infants; Obesity; SAE serious AE.

Fig. 1

Infants’ participation throughout the randomised, double-blind study of infant formula. F1·8, low-protein formula (1·8 g/418·4 kJ (100 kcal)); F2·7, standard-protein formula (2·7 g/418·4 kJ (100 kcal)); IGF-1, insulin-like growth factor-1.

Fig. 2

Daily protein (a) and energy (b) intakes between 0·5 and 1 month (A), 1 and 2 months (B), 2 and 3 months (C), 3 and 4 months (D) and at 6 months (E), 9 months (F) and 12 months of age (G) in infants fed low-protein (F1·8, ) or standard-protein (F2·7, ) formula. Values are means, with standard deviations represented by vertical bars. * Significant difference between feeding groups (P<0·05). To convert kcal/d to kJ/d, multiply by 4·184.

Fig. 3

Weight-for-age (a), length-for-age (b) and head circumference-for-age (c) Z-scores during the first 60 months of life in infants fed a low-protein (F1·8, ) or standard-protein formula (F2·7, ). Values are means, with standard deviations represented by vertical bars. Upper and lower dotted lines indicate +2 sd and −2 sd of the reference group of breast-fed infants, respectively. * Significant difference between the two groups of formula-fed infants (P<0·05). † Significant difference between infants fed F1·8 and breast-fed infants (P<0·05). ‡ Significant difference between infants fed F2·7 and breast-fed infants (P<0·05).