Protein Intake at Breakfast Promotes a Positive Whole-Body Protein Balance in a Dose-Response Manner in Healthy Children: A Randomized Trial.

Background: Protein ingestion promotes whole-body net protein balance (NB) in children, which is a prerequisite for growth. Determining how much protein is required at breakfast to promote a positive NB, which may be negative after the traditional overnight fast in children, has yet to be determined. Objective: We determined the impact of incremental doses of milk protein at breakfast as well as the impact of daily dietary protein distribution on NB in children. Methods: A total of 28 children [14 boys, 14 girls; age range: 7-11 y; body mass index (mean +/- SD, in kg/m(2)): 16.0 +/- 1.9] completed 2 intervention trials. During the breakfast meal, participants consumed an isoenergetic beverage with different amounts of protein (0, 7, 14, or 21 g for Groups A-D, respectively) and [N-15]-glycine to measure whole body protein metabolism. Whole-body nitrogen turnover, protein synthesis (PS), protein breakdown, and NB were measured over 9 and 24 h. Results: Following an overnight fast, children were in negative NB (-64.5 mg . kg(-)(1 ). h(-1)). Protein ingestion at breakfast induced a stepwise increase in NB over 9 h [Groups A (6.2 mg . kg(-1) . h(-1)) < B (279 mg . kg(-)(1 ). h(-1)) < C (46.9 mg . kg(-)(1 ). h(-1)) < D (66.0 mg . kg(-)(1 ). h(-1))] with all conditions different from each other (all P < 0.01). PS was 42% greater in Group D than in Group A over 9 h (P < 0.05). Conclusions: Consuming >= 7 g of the total daily protein intake at breakfast attenuates the observed overnight protein losses in children during the subsequent 9 h following breakfast consumption. The dose-dependent increase in NB over a daytime fed period, inclusive of breakfast and lunch, highlights the importance of breakfast protein intake on acute anabolism in healthy active children.