Similar Muscle Recovery but Greater Soreness in Active Vegans on Low-Protein Diets Compared to High-Protein Omnivores Following Exercise-Induced Damage.

To assess whether a low-protein vegan diet is associated with differences in recovery from exercise-induced muscle damage (EIMD) in physically active individuals. Physically active vegans (n = 7) and omnivores (n = 7) underwent a lower-body muscle damage protocol consisting of five sets of repetitions to failure using the Smith machine squat and leg press at 85% of one-repetition maximum (1RM). Muscle damage and recovery were assessed at baseline, immediately post-exercise, and at 24, 48, and 72 h post-EIMD. Outcomes included serum concentrations of creatine kinase (CK) and lactate dehydrogenase (LDH), delayed-onset muscle soreness (DOMS), countermovement jump (CMJ) performance, and range of motion (ROM). Habitual dietary intake was assessed using four 24-h dietary recalls analysed via the Multiple Source Method (MSM) software. Participants demonstrated similar training volume across exercises and comparable hydration status. Protein intake was significantly lower in vegans (0.98 g/kg) compared to omnivores (2.14 g/kg), along with reduced intake of essential amino acids and, specifically, branched-chain amino acids (p ≤ 0.05). CK levels increased immediately after EIMD and peaked at 24 h, remaining elevated relative to baseline in both groups (p ≤ 0.05). LDH levels rose immediately post-exercise in both groups and were still elevated at 24 h (p ≤ 0.05). DOMS was markedly greater in vegans (+2.7 at 24 h; +2.6 at 72 h on VAS) than in omnivores at 24 and 72 h post-exercise (p ≤ 0.05). While habitually active vegans and omnivores exhibited similar overall responses in muscle damage and recovery following intense resistance exercise, vegans experienced clinically meaningful increases in DOMS. These findings suggest that a low-protein vegan diet may be associated with increased perceived muscle damage, without impairing acute functional recovery. For individuals following a vegan diet, these results highlight the importance of ensuring adequate protein intake and protein quality, including sufficient essential amino acids and branched-chain amino acids, to potentially mitigate exercise-induced muscle soreness and optimise recovery comfort.