Background: Skeletal muscle mass is regulated primarily by muscle protein synthesis, which is optimised via synergistic effects of resistance exercise and dietary protein ingestion. Specifically, increased plasma amino acid availability stimulates muscle protein synthesis. Previous research suggests that whey protein, due to its superior amino acid composition and rapid digestibility, stimulates muscle protein synthesis most effectively. However, certain insect protein sources, such as crickets, possess comparable amino acid profiles to whey, whilst offering greater sustainability. Nevertheless, the efficacy of insect protein ingestion alongside resistance training, to provide necessary amino acids for skeletal muscle development, remains relatively unexplored.
Aim: The purpose of this study was to compare postprandial plasma amino acid availability following insect (cricket) and whey protein ingestion after resistance exercise.
Methods: Using a randomised, crossover design, recreationally active males and females (n = 12; age 25 ± 7 years) ingested 0.4 g·kg body mass-1 of unflavoured whey protein concentrate (WPC) or cricket protein (CP), on separate days, after a bout of full-body resistance exercise. Due to cricket protein’s higher energy density, an additional experimental trial consisting of a quantity of cricket protein that was isocaloric to the whey protein supplement (CPC) was included for each participant. Venous blood samples were obtained immediately prior to supplement ingestion and 20 40, 60, 90, 120, and 180 minutes after. Plasma concentrations of total amino acids (TAA), essential amino acids (EAA), branched chain amino acids (BCAA), and leucine (LEU) were derived from each sample. Ethical approval was granted from the Faculty of Medicine and Life Sciences Research Ethics Committee at the University of Chester, prior to commencing data collection. All data were collected in accordance with the Declaration of Helsinki.
Results: Two-way repeated measures ANOVAs (time [7] x supplement [3]) with post hoc Sidak comparison tests revealed that peak TAA concentrations were greater after WP ingestion than CP (4059 ± 845 vs. 3047 ± 828 µmol·L-1, p = 0.021 ). Peak EAA were higher for WP (1931 ± 409 µmol·L-1) than CP (1097 ± 192 µmol·L-1, p < 0.001) and CPC (1258 ± 275 µmol·L-1, p < 0.001). Peak BCAA were greater after WP (1078 ± 198 µmol·L-1) ingestion compared to CP (559 ± 143 µmol·L-1, p < 0.001) and CPC (593 ± 145 µmol·L-1, p < 0.001). Peak LEU concentrations were higher with WP (391 ± 78 µmol·L-1) compared to CP (164 ± 44 µmol·L-1, p < 0.001) and CPC (178 ± 43 µmol·L-1, p < 0.001). TAA, EAA, BCAA, and LEU overall availability during 180 minutes, expressed as area under the curve, were greater after WP ingestion (591 ± 111, 263 ± 48, 142 ± 20, and 49 ± 8 mmol·180 min·L-1, respectively) compared to CP (523 ± 110, 189 ± 37, 91 ± 17, and 27 ± 5 mmol·180 min·L-1, respectively) and CPC (591 ± 111, 263 ± 48, 142 ± 20, and 49 ± 8 mmol·180 min·L-1, respectively) (p < 0.001 for all).
Conclusions: Ingesting whey protein, post-exercise, elicits greater plasma amino acid bioavailability than an isonitrogenous or isocaloric quantity of cricket protein.