When it comes to building muscle, protein is king. For years, whey protein—which is a byproduct of the dairy industry—has been the number one supplement for weightlifters, especially young men wanting to get strong.
But what if you follow a vegan diet, or you simply want a plant-based alternative? Is there a good option? We are almost always told that plant-based proteins aren’t as well digested and they don’t have the right mix of amino acids to fully support the same muscle growth that you get from whey protein. Whey protein is just superior to plant protein—that’s what we’re always told. But there’s a new myth-shattering study published that shows 45 grams of soy and pea protein work just as well as 45 grams of whey protein for supporting muscle growth in young men who were engaged in resistance training. This study shows that you can build muscle just fine in the real world using plant-based protein powders.
The Study: Comparing Soy / Pea Protein and Whey Protein Head-to-Head
The study, which was published in the Journal of the International Society of Sports Nutrition, recruited 44 healthy young men between the ages of 18 and 35 to be part of this randomized clinical trial. They found healthy young men whose habitual protein intake was just around the RDA, or a little bit less than 1.0 grams per kilo of protein. So they weren’t used to taking a high amount of protein, but they were physically active.
They were assigned to two groups randomly. One of them consumed a pea and soy protein blend and the other consumed whey protein. Both groups consumed 45 grams of their protein supplement each day. They were blended into a drink so that they couldn’t tell which one they had. They drank 1 drink (15 grams of protein) at breakfast, lunch and dinner.
The resistance training program focused on the lower limbs. It consisted of a 45 degree incline leg press and a leg curl exercise, performed on non-consecutive days like Monday, Wednesday, and Friday. So, there was training three times a week. The amount of weights used was increased as the men got stronger and were able to do more reps than called for in the program.
Key outcomes measured included muscle thickness (via ultrasound), strength (one-repetition maximum, or 1RM, for bench press and leg press), and body composition (lean mass and fat mass via dual-energy X-ray absorptiometry, or DXA).
Key Findings: Plant Protein Holds Its Own
The results were clear: both the plant-based and animal-based protein groups experienced comparable improvements in muscle thickness, strength, and lean mass. Specifically:
- Muscle Thickness: Both groups saw significant increases in muscle thickness in thigh muscles (vastus lateralis) with no significant differences between the plant and animal protein groups.
- Strength Gains: Both groups improved their 1RM (one repetition max lift) leg press to a similar extent, showing that plant protein supported strength gains just as effectively as animal protein.
- Body Composition: Lean mass increased similarly in both groups, and fat mass decreases were also comparable, indicating that plant-based protein was just as effective at supporting overall body composition improvements.
The findings from this study challenged the widely held belief that animal-based proteins, especially whey protein, is superior for muscle building. The plant-based soy and pea protein blend, consumed at the same 45 grams per day as the whey protein, provided the necessary amino acids to fuel muscle protein synthesis and hypertrophy just as much as the whey protein did.
Why This Matters: Debunking the Whey Myth
This is really good news for those that want to use plant-based proteins for whatever reason. In the gym, plant proteins are looked down upon and whey protein is what you “have to have” to really build muscles—it has a high leucine content and it digests quickly. Leucine, which is one of the nine essential amino acids, is a key trigger for muscle protein synthesis, which is what you need after the micro-tears made when lifting heavy weights, to encourage stronger muscle growth.
However, modern plant-based protein blends, like the pea and soy protein used in this study, are formulated to provide a complete amino acid profile so that you get sufficient leucine when you eat enough of the powder. You don’t have to use soy protein, you just need a balanced amino acid profile. This can be done with pea protein and rice protein.
Of course, one of the keys to making this work well is to eat enough protein. The participants’ intake in the study was about 1.8 to 2.0 grams protein per kilogram body weight per day. This is the amount of protein that really drove synthesis to help them build muscle—regardless of whether it came from plants or from whey protein. Maybe you could do it with less, but this much did work, so it serves as a great guideline for you and me both.
The results from this study suggest that you don’t need whey protein to achieve great muscle building results. A well-formulated plant-based protein supplement can give you the same benefits, making it a viable option for vegans, vegetarians, or anyone who wants to reduce their reliance on dairy products.
The Bigger Picture
Your meathead friends probably won’t believe you, but this research adds to the growing body of evidence that shows that plant-based nutrition works well in fitness and training. So you can feel confident that a high-quality plant-based protein supplement will work for you to fuel your gains, just as well as if you used whey protein.
You just have to make sure you’re getting enough protein, around 1.6 to 2.2 g/kg body weight per day for muscle building, so choose a supplement that has a balanced amino acid profile and you’re good to go. Your muscles will grow and your whole body will thank you for choosing plant-based nutrition.
Reference: Hevia-Larraín, V., et al. (2025). 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. Journal of the International Society of Sports Nutrition. https://www.tandfonline.com/doi/full/10.1080/15502783.2025.2568047#d1e391
