Are animal or plant proteins better for building muscle? In the battle of the protein sources, everyone’s got an opinion. Fortunately, we’ve got evidenced-based answers that can guide you in designing a diet for maxing out your muscle.
Plant vs. Animal Protein: Why Compare?
Knowing the most effective strategies for building muscle is important. Muscle mass is incredibly beneficial for health. The more muscle you have, the better your life will be:
- Loss of muscle has harmful effects. It’s associated with increased risk of mortality and poor health.
- Muscle protects your metabolism. The more muscle you have, the more calories you burn and the lower your risk of diabetes.
- Sports and fitness are popular activities that are dependent on muscular strength.
There are two ways the body builds muscle. One is resistance training. The other is food intake, primarily eating protein. We know the best programs for packing on muscle. We also need to know which protein foods are best.
Animal Protein Maximizes Muscle
Over the years, research has accumulated showing animal protein is superior for muscle. For example, a 2009 study conducted on Finnish women looked at body composition in omnivores versus vegetarians (1).
The Finnish population is aging, and vegetarianism is increasing. Scientists wondered if the shift toward plant protein would increase the loss of muscle mass with aging. If so, would it lead more people to need long-term care? Are women at greater risk of losing their independence since they are more vulnerable to muscle loss?
This was a relatively small study that included 19 vegetarians and 21 omnivores. The vegetarians had been meatless for an average of 12 years. Results showed that the meat eaters had an average of 4.4 kg (9.6 lbs) more lean mass than the vegetarians. Scientists analyzed body composition using a muscle mass index that measures muscle relative to height. A higher value indicates more lean mass. The vegetarians had a muscle mass index of 6.7 versus 8.3 in the omnivores.
When researchers analyzed diets, they found that the amount of animal protein the women ate was the number one determining factor for muscle. Plant protein had no effect. To give you a better idea of the women’s diets, all women in the study consumed about one gram of protein per kg bodyweight per day. For the vegetarian women, about 0.54 g of this was animal protein (from milk and eggs). For the omnivorous women the figure was 0.71 g.
The researchers suspect that while many traditional plant protein sources contain amino acids, the body doesn't absorb these well in practice. Another possibility is that plant protein has a less anabolic effect because plant proteins contain less of the amino acids leucine, methionine, and lysine. Muscles need these amino acids. Leucine especially is important for muscle building. Muscle protein synthesis is higher the more leucine they get.
Plant vs. Animal Protein Supplementation On Muscle
Of course, this was a relatively small study looking only at women who were not involved in resistance training. What happens when you combine protein with muscle building workouts?
A new meta-analysis provides more insight. This study looked at 18 studies that tested the effect of animal (whey or casein) protein versus plant (pea or soy) protein combined with strength training (2).
Results showed that animal protein led to greater gains in muscle mass compared to plant protein. The effects were most noticeable in younger individuals below age 50. Scientists theorize this is due to “anabolic resistance”—a reduced muscle building response to eating protein that occurs with aging. It may be caused by declining physical activity, prolonged muscle disuse, or inflammation.
A positive finding for strict plant-based eaters: Protein type had no clear impact on strength outcomes. Squat, grip, and leg strength were comparable between groups that supplemented with plant versus animal protein.
After training is an especially important time to consume high-quality protein. Trained muscle is extra sensitive to protein’s amino acids and supplementation may accelerate recovery and lead to greater gains in muscle long term. The good news for vegetarians who aren’t vegan is that you may be able to overcome the drawbacks of plant-based protein in your overall diet by combining strength training with whey or casein protein supplementation.
How Much Total Protein Does The Body Need?
It’s safe to say that animal proteins are more effective for protein synthesis and muscle building than plant proteins. However, this doesn’t mean that vegetarians or plant-based eaters are destined for poor results or frailty.
Several other factors may be just as important as protein source: Total protein intake and protein intake timing.
The total amount of protein you eat is most important: Studies consistently show that you need a minimum of 1.6 g/kg of protein to maximize muscle. You may want to go as high as 2.2 to 2.4 g/kg.
When you eat protein also matters: Protein should be spread out over meals at strategic intervals. By repeatedly stimulating protein synthesis every few hours, you can prevent the body from shifting into a state of protein breakdown. One study found protein synthesis to be significantly higher in response to eating 20 grams every 4 hours over the course of the day compared to a smaller dose of 10 g every 1.5 h or a larger dose of 40 g every 6 hours.
Plant vs. Animal Protein Take Aways:
Protein is the most important macronutrient for optimizing health and function over the lifespan. It’s also vital for athletes who want to enhance physical performance.
Animal proteins are best for building muscle. When eating plant-based proteins, you may need to bump your daily protein goal up from recommended numbers to optimize protein synthesis and muscle development.
Plant-based eaters who aren’t vegan will get muscle benefits from including eggs and dairy. Supplementing with an animal-based whey protein around training will help you reach your anabolic potential.
Strength training makes everything better. Whether you’re building muscle for the first time or want to maintain your lean mass into your twilight years, combining a high-volume weight training program with animal protein will give you the best body composition results.
Contrary to popular belief, animal proteins may be better digested than plant proteins. This translates to easier absorption in the GI tract.
High-quality protein is especially important for older adults. Researchers suggest that taking protein with vitamin D and the supplement HMB may help maintain muscle mass in people over 50.