Pea Protein vs Soy Protein

With the multitude of protein supplement options on the market, you may wonder which to choose. We have reviewed protein supplements in other articles (Hemp Protein vs Whey Protein & Whey Protein vs Plant Protein), but here we’re comparing pea protein vs soy protein.

These are two of the best plant-based protein powder options due to their high-protein content, complete or nearly complete amino acid profile, and effectiveness with muscle strength and growth improvement.

Comparing pea protein vs soy protein

Processing of pea and soy protein into protein powder

Pea protein powder is made from golden or yellow split peas. The process involves mechanically removing the outer shells, then grinding the dry peas into a fine powder. (1)

Soy protein powder is made from soybean meal that remains after the soybeans have been dehulled and defatted. The soybean meal is soaked in water, acid, or alcohol to remove the carbohydrate and fiber so that only the protein portion remains. (2)

Check out our article Whey Protein vs Plant Protein to learn about the processing of whey, brown rice, and hemp protein powder.

Amino acid profile: EAAs & BCAAs

The best protein powders are complete proteins, meaning they contain all 9 essential amino acids (EAAs) in adequate amounts. While all 9 EAAs are important, leucine (a branched-chain amino acid, or BCAA) is shown to encourage a greater rate of MPS compared to the others, so people striving to build muscle should look for protein sources high in leucine, ideally at least 55 mg leucine per gram of protein.

Pea protein is not technically a complete protein because it’s low in methionine, while soy protein is a complete protein. However, pea protein can be combined with brown rice, hemp, or many other protein foods for additional methionine. Additionally, some pea protein powders have methionine added to the formula to make it a complete protein.

Here is a breakdown of the EAA and BCAA content in pea and soy protein (3, 4):

• Pea: Contains all EAAs but is low in methionine
  • Contains all BCAAs, including 71-81 mg leucine per gram of protein (adequate for maximal MPS)
• Soy: Contains all EAAs in adequate amounts
  • Contains all BCAAs, including 68-79 mg leucine per gram of protein (adequate for maximal MPS)

Nutrient profile of pea protein vs soy protein

Both pea protein and soy protein powders are similar in calories, high in protein, low in fat, and low in carbohydrates. However, their micronutrient profiles somewhat differ as noted below:

• Pea: good source of iron and sodium
• Soy: good source of iron, phosphorus, sodium, and zinc

Bioavailability of pea protein vs soy protein

Bioavailability refers to your body’s ability to digest and absorb nutrients from food. When comparing the bioavailability of protein sources, there is an additional consideration of the amino acid profile, specifically regarding essential amino acids.

Soy protein has a higher amino acid score with both of the following methods, though pea protein is close behind and still considered a “good” quality protein source. (5)

Protein Digestibility-Corrected Amino Acid Score (PDCAAS) is a common tool for evaluating protein quality. (6) The PDCAAS measures the amino acids present in the stool and assumes that if no amino acids are present, all amino acids in the food consumed were digested and used by the body. The highest score given is 1.00. According to PDCAAS, soy protein scores 0.98, and pea protein scores 0.89. (7)

Digestible Indispensable Amino Acid Score (DIAAS) is a newer tool for evaluating protein quality and may be more accurate and useful than the PDCAAS. The DIAAS measures the amino acids present in the small intestine (ileum) after protein consumption.

A score of 1.00 is given if all 9 essential amino acids are present in adequate amounts. Protein sources with > 100% of all EAAs will score > 1.00 (animal protein is often > 1.00). According to DIAAS, soy protein scores 0.90, and pea protein scores 0.82. (7)

Digestion & allergy considerations

Both pea and soy are considered medium-digesting proteins, meaning they are digested and available for use by the body at a rate of 4-7 grams per hour. (8)

Protein isolate (both pea and soy) is typically easy to digest for most people, while protein concentrate can cause GI discomfort, like gas and bloating, for those with sensitivities to fiber and starch.

Regarding allergies, soy is one of the top 9 most common allergens, while peas are considered hypoallergenic. However, unless you actually have an allergy to soy, it should be safe to consume.

Taste & texture of pea protein vs soy protein

The taste and texture of pea and soy protein vary between brands and flavor options. Here are the common descriptions from customer reviews online:

• Pea: neutral to mildly sweet and nutty flavor, smooth or fluffy texture that is less chalky than other protein powders
• Soy: neutral to nutty flavor, smooth to medium-grainy texture

Cost of pea protein vs soy protein

The price of soy protein may be a bit higher than pea protein if buying based on weight, but it’s about the same when buying based on grams of protein which is probably the more important comparison. This chart shows the cost of these protein powders from the company Bulk Supplements.

Protein Powder	Price per 2.2 lbs bag	Price per 30 g powder	Price per 25 g protein
Pea protein isolate	$20.96	$0.70	$0.75
Soy protein isolate	$26.96	$0.90	$0.76

Health benefits & potential disadvantages

Pea protein

Pea protein may encourage greater MPS, exercise performance, and recovery than soy protein due to its high amount of arginine (a conditionally-essential amino acid) and leucine (an EAA and BCAA), along with a generally higher concentration of most of the other EAAs. Pea protein has been shown to be as effective as whey protein at building muscle. (9)

There aren’t many disadvantages to pea protein aside from it being a bit low in the EAA methionine, though this can easily be compensated for by consuming a wide variety of protein sources. Like with other plant foods, some people may experience some GI discomfort if they have difficulty digesting fiber or starch, though most of the fiber and starch are removed during the processing of peas into protein powder.

Soy protein

Like pea protein, soy protein is likely to be as effective as whey for muscle and strength gains. (10) Soy protein may also help reduce LDL cholesterol levels and the risk of heart disease and type 2 diabetes. (11, 12)

Soy foods contain soy isoflavones, a class of phytoestrogens, which have estrogenic activity and may reduce the risk of breast and prostate cancers. However, the evidence is limited and some studies show mixed results. There is also the potential for soy isoflavones to alter the body’s own production of estrogen which may be beneficial or harmful depending on the individual. (13, 14)

Of note, soy isoflavones are mostly removed during the processing of soy protein powder, so the estrogenic properties may not be a concern for most people.

Some people may also be concerned with antinutrients, like phytates, lectins, and oxalates, being present in soy. Phytates, lectins, and oxalates can inhibit the absorption of some minerals. While most soy products do contain some antinutrients, soy protein powder is unlikely to have a significant amount since most of the fiber (where antinutrients are found) is removed. (15)

Final thoughts: pea protein vs soy protein

Pea protein and soy protein are both great sources of protein that have been shown to promote muscle growth and strength gains in people who strength train regularly.

For people who are not allergic to soy, both pea and soy are great plant-based options to help meet your protein needs. Since the fiber and starch is mostly removed from protein powder, especially isolates, most people don’t experience digestive issues with either option.

While soy protein powder is more bioavailable and contains sufficient amounts of all 9 EAAs, pea protein is very close behind and most people should be able to meet 100% of their EAA requirement by consuming a variety of protein foods.

For people concerned with the potential estrogenic properties of or the antinutrients present in soy, pea protein may be the better option. Overall, pea protein and soy protein are two of the best vegan protein sources and can be a great addition to most people’s diets.

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