Pea Protein: What It Is and How It Works

Over the past decade pea protein has transformed from a niche product for vegans into one of the most popular plant proteins in sports nutrition. It is added to blends, bars, plant-based «milk», and even meat substitutes. Our editorial team explains what this substance is, how it is produced, and how it works in the body.

What pea protein is

Pea protein is a concentrated protein isolated from the seeds of the field pea (Pisum sativum), most often from yellow split peas. The pea itself contains roughly a quarter protein by dry weight, and the rest is starch, fiber, minerals, and a small amount of fat. The manufacturer’s task is to separate the protein fraction from everything else.

On the market pea protein comes in two main forms: concentrate and isolate. In a concentrate the protein share is lower and more carbohydrates and fiber remain; in an isolate the protein content is usually around 80–85% and higher. Sports nutrition mainly uses the isolate.

The popularity of pea protein is explained by several factors. It contains no lactose, gluten, or soy, so it suits people intolerant of these components. The pea is not on the EU list of 14 major food allergens. In addition, it has a more neutral taste than many other plant proteins and blends well with other ingredients.

For vegetarians and vegans, pea protein is one of the main ways to increase protein intake without animal products. For people who do not restrict animal products, it is an alternative to whey with a different tolerance profile.

How it is produced

The most common industrial method is so-called wet extraction. Peas are dehulled, ground into flour, and mixed with water in an alkaline medium. Under these conditions the proteins go into solution, while starch and fiber remain as an insoluble sediment that is separated by centrifugation.

Next the solution is acidified to the isoelectric point of the proteins — the level of acidity at which they are least soluble and precipitate out. The protein precipitate is separated, washed, neutralized, and spray-dried. This yields the isolate. Some manufacturers additionally use ultrafiltration to increase product purity.

There is also a dry technology — air classification, in which the ground flour is separated into fractions by particle size and density. This yields concentrates with a moderate protein content. This method is cheaper and requires no water or chemical reagents, but the product purity is lower.

An important advantage of industrial processing is the reduction of so-called antinutrients — trypsin inhibitors, phytates, lectins, and some oligosaccharides. In raw peas they reduce protein digestibility and can cause bloating, but during extraction and heating their quantity decreases substantially.

Composition and amino acid profile

The basis of pea proteins is globulins — legumin and vicilin (as well as convicilin) — and, to a lesser extent, albumins. Globulins are responsible for functional properties: the ability to form gels, emulsions, and foam, which matters for the food industry.

From a nutritional standpoint the key is the amino acid profile. Pea protein contains all the essential amino acids, but in different proportions. It is rich in lysine and arginine and has a decent content of branched-chain amino acids. The limiting amino acids for pea are the sulfur-containing ones — methionine and cysteine.

An analysis of commercial plant isolates by Gorissen and colleagues (2018) showed that the content of essential amino acids and leucine in plant proteins is generally lower than in animal proteins, although pea isolate holds one of the better positions among plant proteins. The authors also emphasized that combining different plant proteins makes it possible to bring the profile closer to that of animal protein.

That is why pea and rice are often combined: rice is low in lysine but has relatively more sulfur-containing amino acids, while pea is the opposite. Such a blend has a more balanced profile than each protein separately.

How pea protein works in the body

The mechanism of action of pea protein is the same as that of any dietary protein. In the stomach and small intestine it is broken down by digestive enzymes into amino acids and short peptides, which are absorbed into the blood. From there they travel to the tissues, including the muscles.

In the muscles amino acids serve two functions. First, they are the building material for new proteins. Second, some of them, primarily leucine, act as signaling molecules: they activate the protein complex mTORC1, which triggers muscle protein synthesis (Norton, Layman, 2006). That is why the leucine content of a serving is considered one of the key indicators of a protein’s «anabolic quality».

Since pea protein has somewhat less leucine than whey, a slightly larger serving may be needed for an equivalent signaling effect. Reviews devoted to plant proteins (van Vliet et al., 2015; Pinckaers et al., 2021) mention precisely these strategies for increasing their effectiveness: raising the dose, combining different sources, and enriching with leucine.

Over the long term, when total protein intake is sufficient, pea protein combined with strength training provides muscle mass gains. A randomized study by Babault and colleagues (2015) found no statistically significant difference in the increase in muscle thickness between the pea and whey protein groups over 12 weeks of training.

Strengths and weaknesses

Let us summarize what makes pea protein attractive and what its limitations are.

• Advantages:plant origin, absence of lactose, gluten, and soy; good tolerance in most people; high content of lysine and arginine; moderate price; more environmentally friendly production compared with animal proteins.
• Limitations:lower content of methionine and leucine than in animal proteins; a distinctive «bean» aftertaste; poorer solubility; possible heavy-metal content, which requires quality control of the raw material.

The issue of heavy metals is worth considering separately: plants can accumulate them from the soil, so independent laboratory testing is especially important for plant proteins. Quality manufacturers publish batch analysis results.

Taste and texture are more a matter of habit. Modern isolates are far more neutral than early products, and in blends with cocoa, berries, or plant milk the «bean» notes are barely noticeable.

For people without dietary restrictions, pea protein can be a way to diversify protein sources, and for vegans it can be one of the staples of the diet along with other legumes, grains, nuts, and seeds.

Editorial conclusions

Pea protein is a protein isolated from yellow peas, most often in the form of an isolate with a high protein content. It contains all the essential amino acids but is limited in methionine and has less leucine than whey.

Its mechanism of action is the usual one for a dietary protein: amino acids become building material and a signal for muscle protein synthesis. At a sufficient dose and with regular training, pea protein works in practice.

For maximum effectiveness it is worth combining it with other plant proteins, for example rice, and keeping an eye on product quality.

We also recommend reading our materials «The Benefits of Pea Protein for Athletes: The Evidence Base», «Side Effects of Pea Protein», and «Pea Protein: Available Forms and Which to Choose».

References

1. Babault N, Païzis C, Deley G, et al. Pea proteins oral supplementation promotes muscle thickness gains during resistance training: a double-blind, randomized, placebo-controlled clinical trial vs. whey protein. J Int Soc Sports Nutr. 2015;12(1):3.
2. Gorissen SHM, Crombag JJR, Senden JMG, et al. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids. 2018;50(12):1685–1695.
3. van Vliet S, Burd NA, van Loon LJC. The skeletal muscle anabolic response to plant- versus animal-based protein consumption. J Nutr. 2015;145(9):1981–1991.
4. Pinckaers PJM, Trommelen J, Snijders T, van Loon LJC. The anabolic response to plant-based protein ingestion. Sports Med. 2021;51(Suppl 1):59–74.
5. Norton LE, Layman DK. Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise. J Nutr. 2006;136(2):533S–537S.
6. FAO. Dietary protein quality evaluation in human nutrition: report of an FAO Expert Consultation. FAO Food and Nutrition Paper 92. Rome: FAO; 2013.