BackgroundIt remains unclear whether non–animal-derived dietary protein sources (and therefore vegan diets) can support resistance training-induced skeletal muscle remodeling to the same extent as animal-derived protein sources.MethodsIn Phase 1, 16 healthy young adults (m = 8,f = 8; age: 23 ± 1 y; BMI: 23 ± 1 kg/m2) completed a 3-d dietary intervention (high protein, 1.8 g·kg bm−1·d−1) where protein was derived from omnivorous (OMNI1;n= 8) or exclusively non-animal (VEG1;n= 8) sources, alongside daily unilateral leg resistance exercise. Resting and exercised daily myofibrillar protein synthesis (MyoPS) rates were assessed using deuterium oxide. In Phase 2, 22 healthy young adults (m = 11,f = 11; age: 24 ± 1 y; BMI: 23 ± 0 kg/m2) completed a 10 wk, high-volume (5 d/wk), progressive resistance exercise program while consuming an omnivorous (OMNI2;n= 12) or non–animal-derived (VEG2;n= 10) high-protein diet (∼2 g·kg bm−1·d−1). Muscle fiber cross-sectional area (CSA), whole-body lean mass (via DXA), thigh muscle volume (via MRI), muscle strength, and muscle function were determined pre, after 2 and 5 wk, and postintervention.ObjectivesTo investigate whether a high-protein, mycoprotein-rich, non-animal-derived diet can support resistance training-induced skeletal muscle remodeling to the same extent as an isonitrogenous omnivorous diet.ResultsDaily MyoPS rates were ∼12% higher in the exercised than in the rested leg (2.46 ± 0.27%·d−1compared with 2.20 ± 0.33%·d−1and 2.62 ± 0.56%·d−1compared with 2.36 ± 0.53%·d−1in OMNI1 and VEG1, respectively;P <0.001) and not different between groups (P >0.05). Resistance training increased lean mass in both groups by a similar magnitude (OMNI2 2.6 ± 1.1 kg, VEG2 3.1 ± 2.5 kg;P >0.05). Likewise, training comparably increased thigh muscle volume (OMNI2 8.3 ± 3.6%, VEG2 8.3 ± 4.1%;P >0.05), and muscle fiber CSA (OMNI2 33 ± 24%, VEG2 32 ± 48%;P >0.05). Both groups increased strength (1 repetition maximum) of multiple muscle groups, to comparable degrees.ConclusionsOmnivorous and vegan diets can support comparable rested and exercised daily MyoPS rates in healthy young adults consuming a high-protein diet. This translates to similar skeletal muscle adaptive responses during prolonged high-volume resistance training, irrespective of dietary protein provenance.This trial was registered atclinicaltrials.govas NCT03572127.