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

Protein intake may influence important health outcomes in later life.

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.

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.

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.

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.