Effects of pork protein ingestion prior to and following performing the Army Combat Fitness Test: markers of cognition

Background Military personnel engaged in intense activities must consume enough quality protein in their diet to maintain protein balance and promote recovery. Plant-based proteins are considered lower-quality protein sources than animal proteins due to their lower amount of essential amino acids (EAA) and only containing trace amounts of creatine. The purpose of this study was to determine whether ingestion of military-style meals-ready-to-eat (MREs) containing plant-based (Plant) or pork-based (Pork) sources or protein would affect recovery after the Army Combat Fitness Test (ACFT).Methods Twenty-three (n = 23) Corps of Cadets members participated in a randomized, double-blind, placebo-controlled, and crossover-designed study where they consumed Plant or Pork protein containing MREs. On testing days, participants completed a battery of cognitive function tests (i.e. the trail making test [TMT], Profile of Mood States [POMs], and psychomotor vigilance task test [PVT]) before consuming a pre-exercise meal. After four hours, participants performed the ACFT. Participants were then fed 3 MREs daily containing ≈ 1,250 kcals, 145 g carbohydrate, 45 g protein, 60 g fat, providing 1.7 g/kg/d of protein. Plant-based MREs contained 15.2 g/d (0.20 g/kg/d) of EAA and 0.215 g/d (0.003 g/kg/d of creatine) compared to 22.9 g/d (0.31 g/kg/d) of EAA and 1.82 g/d (0.024 g/kg/d) of creatine in the pork-based MREs. Participants returned to the lab in a fasted condition at 0600 after 24, 48, and 72 hours of recovery while being fed 3 MREs daily and having these markers of cognition assessed. Data were analyzed using general linear model statistics and percentage changes from baseline with 95% confidence intervals.Results Multivariate analysis revealed a time (p < 0.001, ηp2 = 0.281) with no treatment ×time effect (p = 0.330, ηp2 = 0.026) for the TMT, wherein the univariate analysis indicated improvements in the time required to complete TMT tasks A (p < 0.001, ηp2 = 0.386) and B (p < 0.001, ηp2 = 0.214) tests, with no interaction effects observed between treatments (p > 0.05). The percentage change analysis (Figure 1) displays the improvements for time-to-completion of the TMT tasks. Regarding the POMs results, multivariate analysis revealed a time (p < 0.001, ηp2 = 0.128) with no treatment ×time interaction effect (p = 0.927, ηp2 = 0.026). Univariate analysis revealed a decrease over time in vigor ratings (p < 0.001, ηp2 = 0.225) and total mood disturbance score (TMDS, p < 0.001, ηp2 = 0.196) with no treatment ×time interaction effect observed (p > 0.05). Percentage change analysis revealed that depression ratings tended to be lower after 48 hours in the Pork diet (−54 %[−115, 7], p = 0.086) than the Plant diet (p = 0.08), but no differences were found between diets for the TMDS. Lastly, the multivariate analysis revealed no time (p = 0.472, ηp2 = 0.022) with a treatment ×time effect (p = 0.038, ηp2 = 0.044). Univariate analysis revealed an interaction effect in the correct response reaction time (p = 0.002, ηp2 = 0.111), the percentage change analysis showing reaction time for correct responses tended to be slower with pork diet.[Figure: see text]Conclusion Consuming Pork containing MREs for three days following intense military-style training may lessen perceptions of depression but does not appear to improve measures of cognitive function parameters when compared to the Plant-based MREs. While it may be prudent to consume MREs with high-quality protein sources, short-term ingestion of MREs containing protein with higher EAAs and creatine has limited effects on mood states and cognitive function.Registered clinical trial #ISRCTN47322504