Energetic efficiency of infant formulae: a review

Breast-fed and formula-fed infants differ in terms of nutrient intake, growth, and metabolic and endocrine responses. The energetic efficiency, i.e. the weight or length gain per 100 kcal of energy intake, of breast-fed infants is about 11% higher than the energetic efficiency of formula-fed infants. Only limited data is available on the influence of formula composition on the energetic efficiency of infant formulae. We conducted a review of controlled trials to identify the impact of the macronutrient composition of infant formulae on energetic efficiency. An electronic literature search was conducted in February 2014. Intervention trials that investigated the effect of an infant formula with a modified macronutrient composition and reported the weight, length, and nutritional intake of apparently healthy, term, fully formula-fed infants with a normal weight were included. Thirteen trials met the inclusion criteria. The results showed no effect of the total content of energy, carbohydrate, protein, or fat on energetic efficiency. In contrast, small increasing effects of higher glycemic carbohydrates on energetic efficiency were identified. Improved fat absorption via the use of palmitic acid at the sn-2 ester position of triacylglycerol increased the energetic efficiency by 11%. The quality of formula protein, specifically an increased whey-to-casein ratio, an increased α-lactalbumin content, or a higher tryptophan content increased the energetic efficiency by about 13%. We conclude that fat absorption and protein quality have the potential to modulate energetic efficiency and may contribute to the observed differences in growth and metabolism between breast-fed and formula-fed infants.