How Bioavailable Are Plant Proteins?
Credit: Miljan Živković
You’re serious about building muscle, so ensuring your protein is bioavailable is no joke. But how do plant proteins compare to animal-based protein sources? And can plant proteins help with muscle protein synthesis and strength gains?
Whether it’s tempeh, tofu, or even some edamame snacks you’re considering: Here’s what to understand about bioavailability, and when it comes to plant proteins—how they stack up.
(Spoiler: Plant proteins can be just as effective for muscle gains—with bonus benefits. And research proves it. Read on.)
Protein Bioavailability: How Plant Proteins Stack Up
Bioavailability refers to the amount of protein absorbed by your body for muscle protein synthesis. In other words: The amount of protein you consume doesn’t matter as much. Instead, it's about how effectively your body can break that protein down and use the amino acids to repair and build muscle tissue after your workouts.
Bioavailability Scorecard: Plant vs. Animal
The Protein Digestibility Corrected Amino Acid Score (PDCAAS) has typically been the standard for measuring a protein’s amino acid profile and digestibility. Here's how different proteins compare:
Beef/Chicken: 0.92-0.94 PDCAAS
Whey Protein: 1.0 PDCAAS
Soy Protein: 1.0 PDCAAS
Pea Protein: 0.89 PDCAAS
Rice Protein: 0.83 PDCAAS
Hemp Protein: 0.46-0.51 PDCAAS
Animal Protein Truths
We’re not going to lie: There are some advantages with animal-based proteins. The amino acid profiles have ratios that can match what human muscle tissue needs. And because animal proteins lack many of the robust nutrient packages plant proteins carry, they can be easier to digest.
That said, well, they don’t have those stellar nutrient packages—meaning, they don’t have as many vitamins, minerals, and fiber—which can help you feel full, boost your immune function, and reduce inflammation. Plant proteins have a big leg up there.
Here’s more on how plant proteins win.
Leucine: Your Muscle-Building Buddy
Animal proteins typically contain 10-12% leucine by weight, while plant proteins contain 6-8% leucine. Since you need around 2.5-3 grams of leucine per meal to maximally stimulate muscle protein synthesis, you may need to consume 25% more plant protein to hit the same leucine threshold for muscle growth.
For example, 25 grams of chicken breast provides about 2.8 grams of leucine, while you'd need about 30-35 grams of most plant proteins to get the same leucine content. Thing is—that’s not that much. And the benefits that come with consuming plant proteins (e.g.: enhanced recovery for better workouts and hello, more gains) can put those plant protein options on top.
Plant Protein Bioavailability All-Stars
Soy Protein: The Complete Champion
Soy protein stands out as the most bioavailable plant protein, with a PDCAAS score of 1.0—which is the same score as whey protein and chicken, and higher than beef. It contains all essential amino acids and research consistently shows soy protein can stimulate muscle protein synthesis at rates comparable to whey protein (Devries et al., 2018).
The key to maximizing soy protein is to consume enough to hit the body’s leucine threshold. Soy contains about 8% leucine by weight, so you'll need roughly 25-30 grams of soy protein to get the 2.5 grams of leucine needed for optimal muscle protein synthesis stimulation.
If you’re worried about estrogen, pfft. Multiple scientific reviews and meta-analyses have proven the myths about soy protein negatively impacting testosterone levels wrong. In fact, soy protein was not found to impact testosterone, estrogen, or other hormones in healthy men, even at high intakes (Reed et al., 2021; Messina, 2016). So soy up.
Pea Protein: The Rising Star
Pea protein’s popularity has exploded—in part due to its impressive amino acid profile and excellent digestibility. While pea protein isn’t technically complete on its own (it's a little low in methionine), pea protein is rich in branched-chain amino acids, especially leucine, with about 8.4% leucine by weight—making that higher than soy.
When it comes to pumping up, research has shown pea protein to be highly effective for growing muscle. In fact, a 2015 study found that men consuming 25 grams of pea protein twice daily for 12 weeks gained the same amount of muscle mass as those consuming whey protein, with both groups significantly outperforming the placebo group (Babault et al., 2015).
What makes pea protein particularly appealing is its digestibility: It's easily absorbed and gentle on the digestive system, making it an excellent option for those with sensitive stomachs or food allergies.
Rice Protein: The Hypoallergenic Alternative
Brown rice protein has gained attention as a hypoallergenic option that's particularly useful for those with multiple food sensitivities. While rice protein is typically low in lysine, making it incomplete on its own, it's relatively high in other essential amino acids and has shown promising results in research when consumed in adequate amounts.
A notable 2013 study compared rice protein to whey protein in resistance-trained men over eight weeks. Participants consuming 48 grams of rice protein each day saw similar improvements in body composition, muscle mass, and strength compared to those consuming whey protein (Joy et al., 2013).
The key for the guys participating in the study? The higher dose—rice protein's lower leucine content (about 6% by weight) meant participants needed to consume more total protein to achieve the same muscle-building stimulus. That said, it’s not hard to consume a lot of rice protein. In fact, it’s highly soluble, and easily digestible.
Rice protein is often combined with pea protein to create a more complete amino acid profile, with rice protein providing the additional lysine pea protein lacks, and pea protein delivering the methionine that rice protein is short on.
Optimizing Plant Protein for Muscle Growth
Since plant proteins are slightly less bioavailable than animal proteins, you’ll need to make a few minor tweaks when consuming them.
Increase your serving sizes by about 25-30%. For example, if you'd normally consume 25 grams of whey protein post-workout, aim for 30-35 grams of plant protein to compensate for the lower leucine content.
Combine different plant proteins throughout the day to create a more complete amino acid profile. The classic rice and beans combination works because rice provides the methionine that beans lack, while beans provide the lysine that rice lacks. This complementary protein strategy can boost bioavailability across the board.
Plant proteins provide a more sustained release over three to four hours—which can benefit daily muscle protein synthesis. For post-workout nutrition, though, consume your plant protein 30-60 minutes earlier than you would an animal-based protein, to ensure you max peak amino acid availability during your post-workout window.
References
Babault, N., Païzis, C., Deley, G., Guérin-Deremaux, L., Saniez, M. H., Lefranc-Millot, C., & Allaert, F. A. (2015). Pea proteins oral supplementation promotes muscle thickness gains during resistance training: a double-blind, randomized, placebo-controlled clinical trial vs. whey protein. Journal of the International Society of Sports Nutrition, 12(1), 3.
Devries, M. C., Sithamparapillai, A., Brimble, K. S., Banfield, L., Morton, R. W., & Phillips, S. M. (2018). Changes in kidney function do not differ between healthy adults consuming higher-compared with lower-or normal-protein diets: a systematic review and meta-analysis. Journal of Nutrition, 148(11), 1760-1775.
Joy, J. M., Lowery, R. P., Wilson, J. M., Purpura, M., De Souza, E. O., Wilson, S. M., ... & Jäger, R. (2013). The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance. Nutrition Journal, 12(1), 86.
Messina, M. (2016). Soy and health update: evaluation of the clinical and epidemiologic literature. Nutrients, 8(12), 754.
Reed, K. E., Camargo, J., Hamilton-Reeves, J., Kurzer, M., & Messina, M. (2021). Neither soy nor isoflavone intake affects male reproductive hormones: An expanded and updated meta-analysis of clinical studies. Reproductive Toxicology, 100, 60-67.
