For decades, the gym-floor debate has been raging: if you want to maximize muscle growth, you need whey protein. It's been crowned the king of supplements, the gold standard against which all others are measured. Plant-based proteins, meanwhile, have often been viewed as a second-tier option for those with dietary restrictions.
But what if the choice between a scoop of whey and a scoop of a plant-based blend doesn't actually matter for your gains? A brand new study from 2025 puts this exact question to the test, and the results might surprise you.
Disclaimer: This article is a review of the study's abstract, as the full text was not publicly available at the time of writing.
How the Study Was Set Up
Researchers at the Journal of the International Society of Sports Nutrition wanted a direct, head-to-head comparison. They recruited 44 young, untrained men and put them on a serious, 12-week lifting program.
Here’s the breakdown:
- The Training: A supervised, linear periodized resistance training program performed three times per week for 12 weeks. This ensures everyone was training hard and consistently.
- The Participants: Forty-four young men who were new to structured lifting. Using untrained subjects is common in these studies because they have the most potential for rapid muscle growth, making it easier to spot differences between interventions.
- The Supplement: This is the key part. The men were randomly split into two groups. Both groups supplemented their regular diet with an extra 45 grams of protein per day, split into three 15g doses with breakfast, lunch, and dinner.
- Group 1 (ANML): Received an animal-based protein (whey).
- Group 2 (PLNT): Received a mixed plant-based protein blend (soy and pea).
- The Measurements: Before and after the 12 weeks, the researchers measured everything that matters for lifters: muscle size (using DXA scans for lean mass and ultrasound for muscle cross-sectional area) and lower-body strength (a one-rep max leg press).
The Results: Plant vs. Animal Protein for Gains
After 12 weeks of hard training and consistent protein supplementation, both groups made significant progress. This isn't surprising—new lifters on a solid program will always grow. The real question is, did one group grow more?
The answer was a clear no.
Both groups saw statistically significant increases across the board, with no meaningful differences between them.
- Whole-Body Lean Mass: The plant group gained an average of 2.4 kg, while the animal protein group gained 2.5 kg.
- Leg Lean Mass: The plant group added 0.9 kg, and the animal group added 1.3 kg.
- Muscle Size (Vastus Lateralis): The plant group's quad muscle cross-sectional area grew by 0.9 cm², and the animal group's grew by 1.3 cm².
- Strength (Leg Press 1RM): The plant group added an impressive 64 kg to their leg press, and the animal group added 63 kg.
The researchers concluded that there were no statistically significant between-group differences for any of the measured outcomes. Both protein sources performed equally well.
What This Means For You
This study provides strong evidence that when total daily protein intake is sufficient, the source of your supplemental protein may not be the game-changer many believe it to be. Here are the key takeaways for your own training and nutrition:
-
Total Protein is King: The most important factor is hitting your daily protein target. This study used 45 grams of supplemental protein on top of the participants' regular diets. The supplement is just a tool to help you reach your total goal, whether that's 1.6g/kg of bodyweight or higher.
-
Plant-Based Blends Are a Viable Option: If you prefer to avoid dairy or follow a plant-based diet, you can feel confident that a quality blend (like the soy/pea combo used here) can support your muscle-building goals just as effectively as whey.
-
Context Matters: This study used a blend of soy and pea protein. This is important because blending plant proteins helps create a more complete amino acid profile, similar to that of whey. The results might not be the same for a single, lower-quality plant source like rice or hemp protein alone.
Limitations to Keep in Mind
No single study is the final word. It's important to consider the context:
- The participants were untrained young men. The results may not directly apply to highly advanced lifters, women, or older adults, who have different physiological responses to training and nutrition.
- This was a 12-week study. It's possible, though perhaps unlikely, that differences could emerge over a much longer timeframe.
The Bottom Line
Stop stressing about whether your protein shake is made from whey, soy, or pea. This research suggests that as long as you're training hard, eating enough, and hitting your total daily protein goals, a high-quality plant-based protein blend is just as effective as whey for building muscle and strength.
Choose the protein source that best fits your budget, dietary preferences, and digestion. The most important thing is consistency in the gym and in the kitchen.
Reference: Santini MH, Erwig Leitão A, Mazzolani BC, et al. Similar effects between animal-based and plant-based protein blend as complementary dietary protein on muscle adaptations to resistance training: findings from a randomized clinical trial. J Int Soc Sports Nutr. 2025. PMID: 41059835