Mycoprotein ingestion stimulates protein synthesis rates to a greater extent than milk protein in rested and exercised skeletal muscle of healthy young men: a randomized controlled trial.

Background: Mycoprotein is a fungal-derived sustainable proteinrich food source, and its ingestion results in systemic amino acid and leucine concentrations similar to that following milk protein ingestion. Objective: We assessed the mixed skeletal muscle protein synthetic response to the ingestion of a single bolus of mycoprotein compared with a leucine-matched bolus of milk protein, in rested and exercised muscle of resistance-trained young men. Methods: Twenty resistance-trained healthy young males (age: 22 +/- 1 y, body mass: 82 +/- 2 kg, BMI: 25 +/- 1 kg.m(-2)) took part in a randomized, double-blind, parallel-group study. Participants received primed, continuous infusions of L-[ring-H-2(5)]phenylalanine and ingested either 31 g (26.2 g protein: 2.5 g leucine) milk protein (MILK) or 70 g (31.5 g protein: 2.5 g leucine) mycoprotein (MYCO) following a bout of unilateral resistance-type exercise (contralateral leg acting as resting control). Blood and m. vastus lateralis muscle samples were collected before exercise and protein ingestion, and following a 4-h postprandial period to assess mixed muscle fractional protein synthetic rates (FSRs) and myocellular signaling in response to the protein beverages in resting and exercised muscle. Results: Mixed muscle FSRs increased following MILK ingestion (from 0.036 +/- 0.008 to 0.052 +/- 0.006%.h(-1) in rested, and 0.035 +/- 0.008 to 0.056 +/- 0.005%.h(-1) in exercised muscle; P <0.01) but to a greater extent following MYCO ingestion (from 0.025 +/- 0.006 to 0.057 +/- 0.004%.h(-1) in rested, and 0.024 +/- 0.007 to 0.072 +/- 0.005%.h(-1) in exercised muscle; P <0.0001) (treatment x time interaction effect; P <0.05). Postprandial FSRs trended to be greater in MYCO compared with MILK (0.065 +/- 0.004 compared with 0.054 +/- 0.004%.h(-1), respectively; P = 0.093) and the postprandial rise in FSRs was greater in MYCO compared with MILK (Delta 0.040 +/- 0.006 compared with Delta 0.018 +/- 0.005%.h(-1), respectively; P <0.01). Conclusions: The ingestion of a single bolus of mycoprotein stimulates resting and postexercise muscle protein synthesis rates, and to a greater extent than a leucine-matched bolus of milk protein, in resistance-trained young men. This trial was registered at clinical trials.gov as 660065600.