High-Protein Plant-Based Diet Versus a Protein-Matched Omnivorous Diet to Support Resistance Training Adaptations: A Comparison Between Habitual Vegans and Omnivores.
Level 3 - non-randomized controlled study
Prospective non-randomized controlled trial comparing cohorts based on preexisting habitual diet
PubMed 33599941 · doi:10.1007/s40279-021-01434-9
What was done
Thirty-eight healthy young men—19 habitual vegans (mean age 26 ± 5 years) and 19 habitual omnivores (mean age 26 ± 4 years)—completed a 12-week, twice-weekly supervised resistance training program. Baseline habitual protein intake was adjusted to 1.6 g/kg/day using supplemental protein (soy isolate for vegans, whey for omnivores), monitored every 4 weeks. Before and after the intervention, researchers measured leg lean mass, whole muscle cross-sectional area (CSA) of the rectus femoris and vastus lateralis, vastus lateralis muscle fiber type I and type II CSA, and leg-press 1-repetition maximum (1RM).
What was found
Both groups showed significant increases from pre- to post-intervention (all p < 0.05) with no significant between-group differences for any outcome (all p > 0.05): - Leg lean mass: vegan +1.2 ± 1.0 kg vs. omnivore +1.2 ± 0.8 kg - Rectus femoris CSA: vegan +1.0 ± 0.6 cm² vs. omnivore +0.9 ± 0.5 cm² - Vastus lateralis CSA: vegan +2.2 ± 1.1 cm² vs. omnivore +2.8 ± 1.0 cm² - Type I muscle fiber CSA: vegan +741 ± 323 µm² vs. omnivore +677 ± 617 µm² - Type II muscle fiber CSA: vegan +921 ± 458 µm² vs. omnivore +844 ± 638 µm² - Leg-press 1RM: vegan +97 ± 38 kg vs. omnivore +117 ± 35 kg
Why it matters
This study demonstrates that an exclusively plant-based diet is not inferior to an omnivorous diet for building muscle mass and strength during resistance training, provided total daily protein intake is sufficient (~1.6 g/kg/day).
Limits
The study was non-randomized because groups were formed based on preexisting dietary habits. The cohort was small (n = 38) and comprised solely healthy young men, limiting generalizability to women, older populations, or trained athletes. High protein targets were achieved using supplemental protein isolates, so results may not generalize to lower protein intakes or exclusively whole-food vegan diets.
Cited by
- supports There is no difference in muscle size or strength outcomes between plant and animal protein diets.
- supports Clinical trials by Hamilton Roschel and Alistair Monteyne comparing vegan and omnivorous diets at 1.6 to 2.0 g/kg protein intake showed no difference in muscle hypertrophy or strength gains over 10 to 12 weeks of resistance training.