Essential amino acid-enriched whey enhances post-exercise whole-body protein balance during energy deficit more than iso-nitrogenous whey or a mixed-macronutrient meal: a randomized, crossover study

Abstract

Background: The effects of ingesting varying essential amino acid (EAA)/protein-containing food formats on protein kinetics during energy deficit are undetermined. Therefore, recommendations for EAA/protein food formats necessary to optimize both whole-body protein balance and muscle protein synthesis (MPS) during energy deficit are unknown. We measured protein kinetics after consuming iso-nitrogenous amounts of free-form essential amino acid-enriched whey (EAA + W; 34.7 g protein, 24 g EAA sourced from whey and free-form EAA), whey (WHEY; 34.7 g protein, 18.7 g EAA), or a mixed-macronutrient meal (MEAL; 34.7 g protein, 11.4 g EAA) after exercise during short-term energy deficit.

Methods: Ten adults (mean ± SD; 21 ± 4 y; 25.7 ± 1.7 kg/m²) completed a randomized, double-blind crossover study consisting of three, 5 d energy-deficit periods (- 30 ± 3% of total energy requirements), separated by 14 d. Whole-body protein synthesis (PS), breakdown (PB), and net balance (NET) were determined at rest and in response to combination exercise consisting of load carriage treadmill walking, deadlifts, and box step-ups at the end of each energy deficit using L-[²H₅]-phenylalanine and L-[²H₂]-tyrosine infusions. Treatments were ingested immediately post-exercise. Mixed-muscle protein synthesis (mixed-MPS) was measured during exercise through recovery.

Results: Change (Δ postabsorptive + exercise to postprandial + recovery [mean treatment difference (95%CI)]) in whole-body (g/180 min) PS was 15.8 (9.8, 21.9; P = 0.001) and 19.4 (14.8, 24.0; P = 0.001) greater for EAA + W than WHEY and MEAL, respectively, with no difference between WHEY and MEAL. ΔPB was - 6.3 (- 11.5, - 1.18; P = 0.02) greater for EAA + W than WHEY and - 7.7 (- 11.9, - 3.6; P = 0.002) greater for MEAL than WHEY, with no difference between EAA + W and MEAL. ΔNET was 22.1 (20.5, 23.8; P = 0.001) and 18.0 (16.5, 19.5; P = 0.00) greater for EAA + W than WHEY and MEAL, respectively, while ΔNET was 4.2 (2.7, 5.6; P = 0.001) greater for MEAL than WHEY. Mixed-MPS did not differ between treatments.

Conclusions: While mixed-MPS was similar across treatments, combining free-form EAA with whey promotes greater whole-body net protein balance during energy deficit compared to iso-nitrogenous amounts of whey or a mixed-macronutrient meal.

Trial registration: ClinicalTrials.gov, Identifier no. NCT04004715 . Retrospectively registered 28 June 2019, first enrollment 6 June 2019.

Keywords: And energy restriction; Free-form amino acids; Muscle protein synthesis; Whole-body protein turnover.

Fig. 1

Volunteer enrollment and retention

Fig. 2

Schematic of the infusion studies. Muscle biopsy and blood samples were used in combination with primed, constant infusions of L-[²H₅]-phenylalanine and L-[²H₂]-tyrosine to determine the effects of EAA + W, WHEY, or MEAL ingestion on whole-body protein turnover following whole-body exercise as well as mixed muscle protein synthesis throughout an exercise and recovery period during energy deficit

Fig. 3

Mean ± SD (n = 10). Stable-isotope enrichments during the infusion studies

Fig. 4

a: Mean ± SD (n = 10). Postabsorptive plus exercise and postprandial post-exercise recovery whole-body protein synthesis after WHEY, EAA + W, and MEAL intake during energy deficit. *indicates post hoc difference between postabsorptive and postprandial within the same treatment (P = 0.001) and different lowercase letters indicate post hoc difference between treatments within the same condition (both, P < 0.01). b: Mean ± SD (n = 10). Postabsorptive plus exercise and postprandial post-exercise recovery whole-body protein breakdown after WHEY, EAA + W, and MEAL intake during energy deficit. *indicates post hoc difference between postabsorptive and postprandial within the same treatment (P = 0.011) and different lowercase letters indicate post hoc difference between treatments within the same condition (both, P = 0.001). c: Mean ± SD (n = 10). Postabsorptive plus exercise and postprandial post-exercise recovery whole-body net balance after WHEY, EAA + W, and MEAL intake during energy deficit. *indicates post hoc difference between postabsorptive and postprandial within the same treatment (P = 0.001) and different lowercase letters indicate post hoc difference between treatments within the same condition (both, P = 0.001). d: Mean ± SD (n = 10). Change in postabsorptive plus exercise and postprandial post-exercise recovery whole-body protein turnover after WHEY, EAA + W, and MEAL intake during energy deficit. Different lowercase letters indicate difference between treatments within the protein synthesis, protein breakdown, and net balance measures (all, P < 0.05). e: Change in postabsorptive plus exercise and postprandial post-exercise recovery whole-body protein synthesis relative to EAA intake after WHEY, EAA + W, and MEAL intake during energy deficit. Different lowercase letters indicate difference between treatments (all, P < 0.05). f: Mean ± SD (n = 10). Postabsorptive plus exercise and postprandial post-exercise recovery phenylalanine hydroxylation after WHEY, EAA + W, and MEAL intake during energy deficit. *indicates post hoc difference between postabsorptive and postprandial within the same treatment (P = 0.001) and different lowercase letters indicate post hoc difference between treatments within the same condition (both, P = 0.001)

Fig. 5

a Mean ± SD (n = 10). Mixed-muscle protein synthesis responses to whole-body exercise plus post exercise recovery feeding with WHEY, EAA + W, and MEAL intake during energy deficit. No difference between treatments (P = 0.68). b Mean ± SD (n = 10). Relative mixed-muscle protein synthesis responses, expressed relative to study treatment energy, to whole-body exercise plus post exercise recovery feeding with WHEY, EAA + W, and MEAL intake during energy deficit. Different lowercase letters indicate difference between treatment (both, P < 0.05)

Fig. 6

a Mean ± SD (n = 10). Plasma essential amino acid concentrations after WHEY, EAA + W, and MEAL intake during energy deficit. Different symbols indicate post hoc difference (all, P < 0.05) between treatments within a time point. Different lowercase letters indicate post hoc difference between time points within a treatment (all, P < 0.05). b Plasma leucine concentrations after WHEY, EAA + W, and MEAL intake during energy deficit. Different symbols indicate post hoc difference (all, P < 0.02) between treatments within a time point. Different lowercase letters indicate post hoc difference between time points within a treatment (P < 0.03). c Plasma phenylalanine concentrations after WHEY, EAA + W, and MEAL intake during energy deficit. Different symbols indicate post hoc difference (all, P < 0.02) between treatments within a time point. Different lowercase letters indicate post hoc difference between time points within a treatment (P < 0.05). d Plasma tyrosine concentrations after WHEY, EAA + W, and MEAL intake during energy deficit. Different symbols indicate post hoc difference (all, P < 0.04) between treatments within a time point. Different lowercase letters indicate post hoc difference between time points within a treatment (P < 0.03). e Mean ± SD (n = 10). Plasma insulin concentrations after WHEY, EAA + W, and MEAL intake during energy deficit. Different symbols indicate difference between treatment independent of time point (P = 0.04). Different lowercase letters indicate difference between time points independent of treatment (P < 0.01)