Long-term effects of a modified, low-protein infant formula on growth and body composition: Follow-up of a randomized, double-blind, equivalence trial

Abstract

High protein intake in early life is associated with an increased risk of childhood obesity. Feeding a modified lower-protein (mLP) infant formula (1.7g protein/100kcal) until the age of 6 months is safe and supports adequate growth. The aim of the present study is to assess longer-term anthropometry with BMI at 1 and 2 years as primary outcome parameter and body composition in children fed mLP formula. Healthy term-born infants received mLP or control formula (CTRL) (2.1g protein/100kcal) until 6 months of age in a double-blinded RCT. A breast-fed (BF) group served as a reference. Anthropometry data were obtained at 1 and 2 years of age. At the age of 2 years, body composition was measured with air-displacement plethysmography. Groups were compared using linear mixed model analysis. At 1 and 2 years of age, anthropometry, including BMI, and body composition did not differ between the formula groups (n=74 mLP; n=69 CTRL). Compared to the BF group (n = 51), both formula-fed groups had higher z scores for weight for age, length for age, waist circumference for age, and mid-upper arm circumference for age at 1 year of age, but not at 2 years of age (except for z score of weight for age in the mLP group). In comparison to the BF group, only the mLP group had higher fat mass, fat-free mass, and fat mass index. However, % body fat did not differ between feeding groups. In this follow-up study, no significant differences in anthropometry or body composition were observed until 2 years of age between infants fed mLP and CTRL formula, despite the significantly lower protein intake in the mLP group during the intervention period. The observed differences in growth and body composition between the mLP group and the BF reference group makes it necessary to execute new trials evaluating infant formulas with improved protein quality together with further reductions in protein content. This trial was registered in the Dutch Trial Register (Study ID number NTR4829, trial number NL4677). https://www.trialregister.nl/trial/4677.