For increasing muscle mass in healthy adults, which supplement is more effective: whey protein or plant‑based protein?

Whey Protein is Superior for Increasing Muscle Mass

For healthy adults seeking to increase muscle mass, whey protein is the more effective supplement compared to plant-based protein. This recommendation is based on the most recent high-quality evidence demonstrating superior muscle anabolic responses with animal-based proteins, particularly whey 1, 2.

The Evidence Supporting Whey Protein

Animal-based proteins, especially whey, are recognized as high-quality proteins with a biological value of approximately 100, compared to plant-based proteins which range from 80-85 in digestibility 1. The key advantages include:

• Superior essential amino acid profile: Whey contains higher levels of leucine and other essential amino acids critical for muscle protein synthesis
• Better digestibility: Nearly complete absorption versus plant proteins which contain fiber and enzymatic inhibitors that reduce protein digestion 1
• Stronger association with muscle mass: Longitudinal studies show animal protein intake is associated with reduced lean mass loss over 3 years, while plant protein intake shows no such association 1

The most recent 2025 meta-analysis 3 directly comparing plant versus animal protein found that animal protein resulted in significantly better muscle mass outcomes (SMD = -0.20; P = 0.02), with particularly strong effects when comparing whey to non-soy plant proteins like rice, chia, oat, and potato (SMD = -0.58; P = 0.02).

When Plant Protein Can Work

Plant-based proteins are not entirely ineffective, but require strategic optimization 1:

1. Increase the dose: Higher amounts of plant protein can compensate for lower quality
2. Blend multiple plant sources: Combining complementary plant proteins (pea + rice + canola) can match whey's effectiveness 4
3. Add leucine supplementation: Plant protein with added leucine to match whey levels stimulates equivalent muscle protein synthesis 5
4. Combine with resistance training: Recent evidence shows plant protein blends can match whey when paired with structured resistance training 6

Critical Nuances

The soy exception: Soy protein performs better than other plant proteins, showing no significant difference from milk protein for muscle mass in meta-analysis (SMD = -0.02; P = 0.80) 3. However, it still doesn't outperform whey.

Age matters: The muscle mass advantage of animal protein appears stronger in younger adults (<60 years) than older adults (≥60 years), though whey remains the optimal choice across age groups 3, 7.

Cardiovascular considerations: While plant proteins offer lower cardiovascular disease and cancer mortality risk 1, the question specifically addresses muscle mass, not overall mortality. For pure muscle-building goals, whey wins.

Common Pitfalls to Avoid

• Don't assume all plant proteins are equal: Non-soy plant proteins (rice, pea, potato alone) are significantly inferior to whey 3
• Don't use inadequate doses: If choosing plant protein, you must consume higher amounts than whey to achieve similar effects 1
• Don't ignore leucine content: This is the primary driver of the whey advantage; plant proteins without leucine fortification will underperform 5

Practical Recommendation Algorithm

Choose whey protein if:

• Maximum muscle mass gain is the priority
• No dietary restrictions prevent animal protein consumption
• Cost is not prohibitive

Choose plant protein blends (pea + rice + canola or similar) if:

• Ethical or environmental concerns are paramount
• Willing to consume 20-30% higher doses
• Can ensure leucine content matches whey (add 2.5g leucine per serving if needed) 1
• Combining with structured resistance training 6, 4

Avoid single-source plant proteins (rice alone, pea alone, potato alone) as these show the poorest outcomes compared to whey 3.

The 2024 network meta-analysis of 78 RCTs involving 5,272 participants definitively ranked whey as the most effective protein supplement for augmenting muscle mass (SUCRA = 0.86), handgrip strength (SUCRA = 0.85), and walking speed (SUCRA = 0.84) when combined with resistance training 7.