Plant Protein versus Dairy Protein for Muscle Building

January 22, 2014

Protein, sports nutrition’s heavy hitter, continues to win, with double-digit sales gains and an outflux of high-protein product claims. “High-protein intake is trending with most consumers,” says Scott Steil, president of Nutra Bridge Corp. (Shoreview, MN).

A formulator has many protein options these days. Ahead is a quick rundown, including what the latest studies say.


Protein is rich in essential amino acids—particularly, the branched chain amino acids (BCAAs) leucine, isoleucine, and valine, which are highly concentrated in muscle tissue. “BCAAs play a special role in muscles because they can be metabolized within the muscles—rather than in the liver, where all other aminos are metabolized—and be used for energy,” says Scarlett Blandon, registered dietitian for Axiom Foods (Los Angeles). BCAAs play a key role in muscle recovery/synthesis and sports performance.1

How do BCAAs compare in different protein sources—specifically dairy and plant?

BCAAs are very high in dairy protein compared to other protein sources2,3, says Bryan Helwig, PhD, director of nutrition research for the Dairy Research Institute (Rosemont, IL). Where dairy proteins are considered “complete” because they contain all nine essential amino acids, most plant proteins (including beans and peas, seeds, nuts, vegetables, and grains) are considered “incomplete”—and even plant proteins that are considered complete still have lower BCAA levels compared to dairy, he says.

Dairy, and whey especially, is high in leucine compared to other proteins. Leucine is linked to increased muscle protein synthesis when consumed as part of a resistance-training program4, Helwig says.

Brown rice protein and pea protein comprise about 19% and 18% BCAAs, respectively, Axiom’s Blandon says. These percentages are comparable to dairy protein casein, which is typically 20% BCAAs, she adds. Axiom offers Oryzatein brown rice protein, Veg-O-Tein P yellow pea protein, and Incatein Sacha Inchi protein.

Plant proteins boast other amino acids as well. Take soy. “Soy has different amino acid ratios than whey, including greater levels of glutamine and arginine,” says Tom Burrows, director of strategic marketing, ADM Soy Proteins (ADM; Decatur, IL). Glutamine, for example, may help prevent fatigue in athletes.

Wheat protein is rich in glutamine—nearly double that of soy and whey, according to supplier MGP Ingredients (Atchison, KS). Last year, the company introduced Optein hydrolyzed wheat protein for post-workout muscle recovery.

Pea protein offers glutamine, arginine, and lysine, says Neelesh Varde, PhD, senior product manager for Roquette America (Keokuk, IA). Roquette supplies Nutralys pea protein, which is an isolate (85% protein) and naturally high in BCAAs (18%).

Rice protein can sometimes be lower in lysine, but supplier AIDP (City of Industry, CA) uses sprouting to enrich the lysine content of its recently launched Gabiotein rice protein, making it a complete protein, the firm says.


There are fast-digesting proteins and slow-digesting proteins. Which is desirable? It depends on the goal.

Whey protein digests quickly, making amino acids and their muscle-repairing benefits quickly available to the body—desirable for post-workout recovery, for instance. Casein, by contrast, is slower to digest. (Some studies also suggest that consuming whey protein during and/or after exercise may improve strength and support muscle function and fatigue, but more research is needed here, says Kara McDonald, director, U.S. ingredients marketing and communications, U.S. Dairy Export Council (Arlington, VA).
Soy protein digests slower than whey protein, and there may be benefits to that, says ADM’s Burrows: “This enables more prolonged absorption.”

Digestion ease and efficacy are also key. Protein digestibility is most commonly measured by a ratings system called the Protein Digestibility Corrected Amino Acid Score (PDCAAS). (Read more about PDCAAS—and its possible replacement—in the sidebar below.) Burrows says isolated soy protein is the only vegetable protein whose PDCAAS score compares with animal proteins.

Hemp is considered a slow-digesting protein according to PDCAAS, says Richard Pierce, president of Canadian supplier GFR Ingredients. Last year, the company introduced a water-soluble hemp protein powder, HempSol-65, which it calls the most-concentrated hemp protein powder on the market. The company manufactures out higher percentages of hemp seed shell, which it says lowers carbohydrate levels and enables higher protein content. Also, hemp has an 87% Biological Value (BV) score (a measure of protein absorption), which Pierce says is lower than whey or rice’s but significantly higher than soy’s. Hemp is considered a complete protein, containing all nine essential amino acids.

Nutralys pea protein is a “fast-intermediate” digesting protein, says Roquette’s Varde. He ranks it between whey and casein, with a digestion window of 20 minutes to 8 hours. Varde offers other Nutralys numbers: 98% fecal digestibility, 89% gastroileal digestibility, and 78% postprandial nitrogen retention compared to other plant and dairy proteins.

Pea is Vega’s protein of choice for its plant-based recovery drink mix, Vega Sport Recovery Accelerator. “Pea protein supplies an easily digested source of BCAAs, which act as signaling molecules to transition muscles from a catabolic state (breaking down) to anabolic (building up)”5—key for the product’s recovery benefits, says Emma Cutfield, Vega’s innovation manager. (Sales of Vega products currently comprise 30% of all plant-based protein sales in the U.S. natural channel, she says.) Designed for use in the 20-minute window immediately following a workout, Vega Sport Recovery Accelerator provides a specific 4:1 ratio of carbohydrates-to-protein to enhance muscle glycogen synthesis and therefore muscle recovery6, she says. She adds that pea protein is more soluble for drinks than other plant proteins.

Enzymes aid protein’s amino acid release. “For sports, enzymes are being used in several ways, which include nutrient delivery and energy metabolism, as well as post-workout recovery support. One interesting new trend is the use of proteases to release amino acids more quickly, especially the BCAA leucine,” says Richard Mihalik, director of innovation and product development, National Enzyme Co. (NEC; Forsyth, MO). In vitro tests show that NEC’s BioCore Edge enzyme blend breaks down whey protein quicker, reducing the size of protein molecules and speeding the release of BCAAs, he says.

Plant proteins tend to release their amino acids more slowly compared to whey protein, so enzymes are important here if the goal is a quick release, Mihalik says. “Plant-based proteins have the most to gain from targeted protease blends like BioCore Edge,” he says.

Finding the right blend of proteases to make a specific protein/protein blend digestion-friendly requires knowing which amino acid bonds and sequences make the protein resistant to digestion. For instance, “less processed” plant proteins may have significant fatty acid and carbohydrate residue that makes digestion inefficient, Mihalik says. "Soy protein tends to be more resistant to our natural digestive enzymes, so adding appropriately selected proteases may accelerate the release of amino acids, making them more rapidly available for absorption," he says. And proteases may act differently on different protein sources. “Even proteins of the same type can behave differently depending on how a manufacturer processes them.”