To read the full abstract: Am J Clin Nutr. 2019;109:11541163.
Early life nutrition has long-term effects on body composition and obesity risk. Breastfed infants have a lower risk of obesity, which may be related to the lower protein intake in human milk compared to infant formula. Recent studies have confirmed the association between high-protein intake during the first years of life and rapid growth rate and later obesity . Avoiding high-protein intake in early life may thus represent a strategy to prevent childhood obesity . The insulin-like growth factor (IGF) axis is sensitive to the nutritional status  and may represent the link between early nutrition and later body composition and growth. For instance, IGF-I levels during infancy are higher in non-breastfed infants and are related to later increase of linear growth .
This study included 1,165 US children of the Boston-area Project Viva (NCT02820402), a prospective cohort study of motherchild pairs examining associations of prenatal, perinatal, and early-life exposures with pregnancy and child health outcomes. The aim of this study was to investigate the association between protein intake early after infancy and later growth and body composition. The protein intake in early childhood (median 3.2 years) was tested for association with anthropometry, body composition and IGF-I concentrations in mid-childhood (median 7.7 years) and early adolescence (median 13 years). Several potential confounders (i.e. race, sociodemographic factors, parental and birth size, breastfeeding, physical activity and fast food intake) were included in the analysis.
Early protein intake was not associated with any of the mid-childhood parameters. Only in males, each 10-g increase in animal protein intake in early childhood was associated with higher BMI z-score (+0.12), lean mass (+1.34%) and IGF-I (+5.67%) in adolescence, suggesting that early protein intake may affect to a certain extent the puberty-related growth in boys. No association was observed in girls. A reasonable explanation for this sex dimorphism is that these early adolescent features may be driven primarily by pubertal sex steroids in girls. In boys, who have less advanced puberty in early adolescence, these features may be more strongly influenced by early life factors such as protein intake.
The major limitation of the study is the evaluation of dietary intake by Food Frequency Questionnaires that may have led to a possible over-reporting of protein intake. Furthermore, no information about child diets after early childhood was available and hence included in the analysis, thus leaving open the possibility of a major effect of mid-childhood and early-adolescence protein intake on the measured outcomes.
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