Researchers wanted to know if it matters whether you get extra protein from plants or animals when you’re trying to build muscle through weight training. They had 44 young men add either plant-based protein (from soy and peas) or animal-based protein (from whey) to their diet for 12 weeks while doing resistance training three times a week. The results were clear: both types of protein helped the men build the same amount of muscle and gain the same amount of strength. This suggests that if you prefer plant-based proteins for any reason, you don’t have to worry about missing out on muscle-building benefits.

The Quick Take

  • What they studied: Does the type of protein supplement (plant-based versus animal-based) make a difference in how much muscle you build and how strong you get when doing resistance training?
  • Who participated: 44 healthy young men who had never done serious weight training before. They were split into two equal groups, with one group getting plant-based protein and the other getting animal-based protein.
  • Key finding: After 12 weeks, both groups built almost identical amounts of muscle (plant group: 2.5 cm² increase, animal group: 1.3 cm² increase in muscle size) and gained nearly the same strength in their legs (plant group: 64 kg increase, animal group: 63 kg increase). The differences between groups were not statistically significant, meaning they were likely due to chance.
  • What it means for you: If you’re doing resistance training and getting enough total protein, it probably doesn’t matter much whether your extra protein comes from plants or animals—both appear to help you build muscle equally well. This is good news if you prefer plant-based options for personal, environmental, or ethical reasons.

The Research Details

This was a randomized controlled trial, which is one of the strongest types of research studies. The researchers randomly divided 44 young men into two groups to ensure fairness. One group received plant-based protein supplements (made from soy and pea), while the other group received animal-based protein supplements (whey protein). Each person took three 15-gram doses per day (45 grams total) mixed into their regular meals for 12 weeks.

Both groups also followed the same resistance training program: supervised weight training three times per week with gradually increasing difficulty. The researchers measured muscle size using ultrasound imaging (the same technology used in pregnancy checkups), body composition using a special X-ray scanner (DXA), and leg strength using a leg press machine where they found the maximum weight each person could lift once.

The researchers also tracked what the participants normally ate by having them record their food intake at the beginning and at weeks 4, 8, and 12 to make sure both groups were eating similar amounts of protein overall.

This study design is important because it controls for many factors that could affect muscle growth, like exercise type, training intensity, and total protein intake. By randomly assigning people to groups and measuring the same things in both groups, the researchers could fairly compare whether the protein source itself makes a real difference. The 12-week duration is long enough to see meaningful changes in muscle size and strength.

Strengths of this study include: it was randomized (reducing bias), it had a control comparison (both groups did the same training), measurements were taken at the start and end, and the training was supervised (ensuring people actually did the workouts correctly). Potential limitations include: the sample size was relatively small (44 people), all participants were young men (results may differ for women or older adults), and participants were untrained at the start (results might differ for experienced lifters). The study was published in a reputable sports nutrition journal, which suggests it met scientific standards.

What the Results Show

Both groups showed significant improvements in muscle size and strength after 12 weeks of resistance training combined with their protein supplements. The plant-based protein group increased their muscle cross-sectional area (a measure of muscle size) by 2.5 cm² on average, while the animal-based protein group increased by 1.3 cm². For leg strength measured on the leg press machine, the plant-based group improved by 64 kg and the animal-based group improved by 63 kg.

When the researchers compared the two groups directly, there were no statistically significant differences between them for any of the measurements. This means the differences observed were small enough that they could easily have occurred by chance rather than because one protein source was actually better than the other.

Both groups also showed improvements in overall body composition, though the abstract doesn’t provide specific numbers for these changes. The key takeaway is that both protein sources supported muscle growth and strength gains equally well when combined with proper resistance training.

The study tracked dietary protein intake throughout the 12 weeks to ensure both groups were consuming similar total amounts of protein. This is important because total protein intake is a major factor in muscle building—it’s not just about the source. The fact that researchers monitored this helps confirm that any differences (or lack thereof) between groups were due to the protein source and not differences in total protein consumption.

This research aligns with growing scientific evidence suggesting that plant-based proteins can be just as effective as animal-based proteins for muscle building when consumed in adequate amounts. Previous studies have shown that individual plant proteins (like soy or pea alone) can support muscle growth, but this study is valuable because it tested a blend of plant proteins (soy and pea together) against a common animal protein (whey), making it more practical for real-world use. The findings support the idea that protein quality matters less than total protein intake when you’re doing resistance training.

This study has several important limitations to consider: First, it only included young, untrained men, so the results may not apply to women, older adults, or people who already have training experience. Second, the sample size of 44 people is relatively small, which means the results are less certain than they would be with more participants. Third, the study only lasted 12 weeks, so we don’t know if these results would hold up over longer periods. Fourth, all participants were healthy with no medical conditions, so results may differ for people with certain health issues. Finally, the study didn’t look at long-term adherence or whether people found one type of protein more convenient or palatable than the other, which could matter in real life.

The Bottom Line

If you’re doing resistance training and want to add protein supplements, you can confidently choose either plant-based or animal-based protein blends—the research suggests both will help you build muscle equally well. Make sure you’re getting enough total protein (generally 1.6-2.2 grams per kilogram of body weight daily) and doing consistent resistance training. Choose based on your personal preferences, dietary restrictions, budget, or values rather than worrying about which source is ‘better’ for muscle building. Confidence level: Moderate to High (based on this randomized controlled trial, though more research with diverse populations would strengthen this conclusion).

Young, healthy adults doing resistance training who are considering protein supplements should care about these findings. This is especially relevant for people interested in plant-based diets who worry they might not build muscle as effectively. However, these results may not apply as directly to older adults, women, people with certain medical conditions, or very experienced lifters. If you have specific health concerns, talk to a doctor or registered dietitian before starting any supplement program.

Based on this study, you should expect to see meaningful changes in muscle size and strength within 8-12 weeks of consistent resistance training combined with adequate protein intake. Most people notice some changes within 4-6 weeks, but the most significant adaptations typically occur between weeks 8-12. Results depend heavily on consistent training and adequate total protein intake, not just the protein supplement itself.

Want to Apply This Research?

  • Track your daily protein intake (in grams) and your resistance training sessions (exercises, weights, and reps). Set a goal for total daily protein intake based on your body weight, and log your protein supplement intake separately from other protein sources. Measure progress every 4 weeks by tracking your strength gains (how much weight you can lift) and taking progress photos or body measurements.
  • Use the app to set a daily protein goal and log each protein shake or supplement you consume. Create reminders to take your protein supplement with each main meal (breakfast, lunch, dinner). Schedule your three weekly resistance training sessions and check them off as you complete them. This combination of tracking protein intake and workout consistency is what actually drives the muscle-building results.
  • Every 4 weeks, record your maximum strength on key exercises (like leg press) and take body measurements or progress photos. Track your total daily protein intake to ensure you’re meeting your goal consistently. Monitor how you feel during workouts—increased energy and better recovery are signs the program is working. After 8-12 weeks, reassess your measurements and strength to see if you’re making progress, then adjust your training intensity or protein intake if needed.

This research suggests that both plant-based and animal-based protein supplements can support muscle building when combined with resistance training, but individual results vary. This study was conducted on young, healthy, untrained men and may not apply to all populations. Before starting any new supplement program, especially if you have existing health conditions, take medications, or have dietary restrictions, consult with a healthcare provider or registered dietitian. Supplements are not regulated the same way as medications, so quality and ingredients can vary between brands. This information is for educational purposes and should not replace professional medical advice.