Protein Concentration in Milk Formula, Growth, and Later Risk of Obesity: A Systematic Review

Background: Protein intake may influence important health outcomes in later life.

Objective: The objective of this study was to investigate current evidence on the effects of infant formulas and follow-on formulas with different protein concentrations on infants' and children's growth, body composition, and later risk of overweight and obesity.

Methods: In this systematic review, we searched electronic databases (including MEDLINE, Embase, and the Cochrane Library) up until November 2014 for randomized controlled trials (RCTs). Eligible studies had to include children aged 0-3 y who represented the general population and were fed cow milk-based infant formulas with variations in protein concentration. Control groups received lower-protein cow milk-based formulas (as defined by the authors). The primary outcomes were growth, overweight, obesity, and adiposity. Various time points for outcomes assessment were accepted for inclusion. If possible, a meta-analysis was performed.

Results: Twelve RCTs met our inclusion criteria. Different formula protein concentrations did not affect linear growth other than a transient effect on mean length at 3 mo observed in a meta-analysis of 4 studies (mean difference, - 0.27 cm; 95% CI: -0.52, -0.02). Lower mean weight and weight z scores obtained from the infants fed lower-protein formulas were observed only from 6 to 12 mo of age. Data from one large RCT showed that consumption of a lower-protein infant formula may reduce body mass index at 12 mo of age and later (12 mo, 24 mo, and 6y) and the risk of obesity at 6 y. Effects on body composition remained unclear.

Conclusions: The current evidence is insufficient for assessing the effects of reducing the protein concentration in infant formulas on long-term outcomes, but, if confirmed, this could be a promising intervention for reducing the risk of overweight and obesity in children. In view of the limited available evidence, more studies replicating effects on long-term health outcomes are needed.