Plant vs Animal Protein: Which Builds Muscle Better?
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For years, gym-goers and athletes have debated which protein is better for building muscle: plant or animal. Many believe animal-based sources like whey, eggs, or meat have an advantage because they contain all essential amino acids in the right balance. However, new research from the University of São Paulo challenges that belief. The study found that a blend of plant proteins can be just as effective as animal protein for muscle growth and strength, when total protein intake is sufficient.
What Did the Study Investigate?
Researchers compared the effects of plant and animal protein supplementation on muscle gains during a 12-week resistance training program. Forty-four young, healthy men who had not trained with weights before were divided into two groups. One group consumed a plant-based blend of soy and pea protein, while the other consumed whey protein, an animal-based source.
Both groups took 45 grams of protein per day (15 g each with breakfast, lunch, and dinner) and trained three times a week under supervision.
Before and after the 12 weeks, scientists measured muscle mass, muscle size (using ultrasound), and strength (through leg press tests). They also monitored diet to ensure everyone consumed about 1.6 grams of protein per kilogram of body weight per day, which is the optimal intake for muscle growth.
The Results: No Difference Between Plant and Animal Proteins
At the end of the study, both groups showed impressive improvements in muscle mass and strength. The increases were nearly identical:
- Whole-body lean mass increased by about 2.4–2.5 kg
- Leg muscle size (vastus lateralis) grew by roughly 0.9–1.3 cm²
- Leg press strength (1RM) improved by around 60–65 kg
There were no significant differences between those using plant-based protein and those using whey. Even though plant proteins generally have lower levels of certain amino acids like leucine, combining soy and pea created a balanced amino acid profile that supported muscle growth just as well as whey.
Why These Findings Matter
This study adds to a growing body of research showing that plant proteins can effectively support muscle building. It’s not the source of protein that matters most, it’s the total amount and quality. When plant proteins are combined in the right ratios and consumed in sufficient amounts, they can provide all the amino acids your body needs for muscle repair and growth.
For those following vegetarian or vegan diets, this is great news. It means muscle gains are achievable without relying on animal products, as long as you pay attention to variety and protein quantity.
The Science Behind It
Muscle growth happens when the body’s rate of muscle protein synthesis (MPS) exceeds the rate of breakdown. The amino acid leucine plays a crucial role in triggering MPS. Animal proteins like whey are rich in leucine, but the plant blend in this study contained similar leucine levels, which might explain the equal results.
Additionally, combining different plant proteins improves digestibility and balances their amino acid profiles. Soy and pea proteins complement each other—soy provides more lysine while pea contributes methionine and cysteine—making the blend more “complete.”
What This Means for You
If you’re someone who lifts weights or does resistance training, here are some takeaways:
- Focus on total daily protein: Aim for about 1.6–2.0 g of protein per kilogram of body weight each day.
- Use a mix of sources: Combining plant proteins like soy, pea, rice, or hemp can improve amino acid balance.
- Time your intake: Distribute protein evenly across meals to keep MPS elevated throughout the day.
- Don’t stress the source: Whether you choose whey or plant-based protein, both can deliver great results if the rest of your diet is balanced.
Limitations to Keep in Mind
The study included only young, healthy men eating an omnivorous diet. It didn’t test the effects in women, older adults, or strict vegans. Also, the focus was mainly on leg muscles, not the entire body. Despite these limits, the findings strongly suggest that both plant and animal proteins are equally effective for supporting resistance training outcomes.
The Bottom Line
This research provides solid evidence that you don’t need animal protein to build muscle. When consumed in adequate amounts and combined with regular strength training, plant-based proteins especially blends like soy and pea are just as effective for muscle gain and strength improvement as whey.
In short, it’s not about where your protein comes from, but how much and how consistently you get it.
