Plant Protein vs. Whey: Which Is Better for Building Muscle?
Is plant protein (pea, soy, rice) really inferior to whey protein for building muscle? A new systematic review with meta-analysis published in the Journal of the Academy of Nutrition and Dietetics (27 April 2026) has just provided the most detailed answer yet, based on 12 studies and 26 effect sizes in adults aged 18-85.
Key results from the new systematic review
The authors (Mendes, Correia, Santos, Schoenfeld, Swinton, Mendonca) used a 3-level Bayesian model to compare the degree of muscle protein synthesis (MPS) stimulation between animal and plant protein. Result: animal protein was only very slightly superior — an effect size of just 0.004 (95% CI: -0.002 to 0.011) — and the certainty of this evidence was rated low due to data heterogeneity.
What actually matters
- Total daily protein: hitting your overall protein target (1.6-2.2 g/kg/day for most people training) matters far more than the source of that protein.
- The leucine threshold: plant proteins tend to be lower in leucine, the amino acid that most directly triggers MPS. Aim for roughly 2-3 g of leucine per meal — often meaning slightly larger servings of plant protein.
- Protein quality and completeness: combining different plant sources (e.g., pea + rice, or soy) provides a complete amino acid profile, eliminating most of the theoretical gap.
- Practical equivalence: for most lifters, a well-planned plant-based diet with adequate total protein produces muscle gains comparable to a whey-based diet.
Practical takeaways
Choose the protein source that fits your diet, preferences, and budget. If you're plant-based, pay attention to getting enough total protein and consider slightly larger portions to cover the leucine threshold — and if you want, a plant-based protein powder (pea, soy, or a blend) makes hitting daily targets easy. The evidence no longer supports the idea that whey is meaningfully superior for muscle building.
This article summarizes general scientific findings and is not a substitute for individualized medical or dietary advice.
Helpful products
- Pea protein powder — a convenient plant-based option for hitting daily protein targets.
- Whey protein isolate — a fast-digesting, convenient option if you prefer dairy-based protein.
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