Soy Protein vs Pea Protein: Which Powder is Better?

UK Fitness Pro
UK Fitness Pro
· 12 min read
An image representing a comparison between soy protein and pea protein

For years, my go-to protein powder has been Myprotein's whey protein concentrate

As discussed in my article comparing whey and egg protein, whey is a very high-quality protein. But it does give me some—let's say—"digestive issues". In light of these, I am interested in replacing some of my whey protein powder with a plant-based protein powder, such as a pea protein isolate or soy protein isolate. 

However, I would want to know if the alternative is comparable to whey in terms of its amino acid composition and protein content and its capacity to support muscle growth and athletic performance, so let's look at some evidence...

What is Soy Protein Powder?

Soy protein powder is made by extracting protein from soy beans to create soy protein concentrate, which is then processed and dried into a fine powder form. (However, there are slight differences in how soy concentrate and isolate are made.)

What is Pea Protein Powder?

Pea protein powder is produced by grinding yellow peas or yellow split peas into flour, from which pea protein concentrate is derived; this concentrate can then be further processed to create pea protein isolate, which is finally dried and milled into pea protein powder.

A pea protein supplement

My pea protein isolate sample from Myprotein. I enjoyed this more than expected. The strawberry flavour is very sweet, but it combines surprisingly well with the earthy taste that pea protein powder has naturally. Currently, you can get this sample for less than a pound. If you'd prefer a more neutral taste, you can get the larger bags in "unflavoured". 

Amino Acid Profile

Essential amino acids are those the human body cannot synthesise itself, meaning we need to get them from our diet. As soy protein has a complete amino acid profile, it could be described as a complete protein source (1). Likewise, pea protein is a complete protein and it actually has a little more of most essential amino acids than soy protein (2). 

Figure 1. Amino Acid Profile of Pea Protein and Soy Protein

Graph showing essential amino acid profiles of soy and pea proteins

As you can see, both proteins have a good amount of the essential nutrient leucine (however, whey has about 50% more), a branched-chain amino acid (BCAA) linked to muscle protein synthesis (3) and increases in endurance and power (4). If you'd like to learn more about BCAA supplements, I've also written articles comparing BCAAs and essential amino acids, BCAAs and beta-alanine, BCAAs and whey protein, BCAAs and pre-workout, BCAAs and glutamine, BCAAs and creatine, BCAA pills and powders, and EAAs and protein powders, as well as an article on the benefits of BCAAs for athletes

Soy and Pea Powders as Sources of Protein

As per the Mayo Clinic guidelines for someone who lifts weights, I aim for 1.7 grams of protein per kilo of body weight per day. 

At 95 kilos, this means about 160 grams. As you can see in the table below, pea and soy protein powders normally provide at least 80 grams of protein per 100 grams (which is similar to whey protein powders). Assuming 30-gram scoops, I'd need about 6.5 scoops to reach my protein intake target. 

I wouldn't completely rely on a protein supplement to ensure I get enough protein as it's important to also consume real foods with high protein content as these will have important micronutrients, but either soy or pea protein powder would be a great help if you're struggling to meet your targets. 

Table 1. Calories and Grams of Macronutrients per 100 Grams in Pea and Soy Protein Powders From Myprotein (MP) and Bodybuilding Warehouse (BW)

SupplementCaloriesProteinCarbsFats
BW Pea Protein Isolate3958036
MP Pea Protein Isolate388802.65.5
BW Soy Protein Isolate3689061
MP Soy Protein Isolate360901.81.5

Supporting Muscle Mass

Soy Protein Powder

In a study published in the International Journal of Sport Nutrition and Exercise Metabolism (5), participants either received whey protein, soy protein, or a placebo and underwent a 6-week training regimen, with assessments conducted before and after the programme on muscle mass and strength. The findings indicated that whey and soy protein supplements significantly improved muscle mass and strength compared to the placebo.

You might also like my article comparing soy and whey protein powders

Pea Protein Powder

One study published in the Journal of the International Society of Sports Nutrition (6) compared how pea protein, as opposed to whey protein and a control group, impacts muscle size among men engaged in a 12-week weightlifting programme, with each taking 25 grams of their given supplement twice a day. The results showed that those who took pea protein, especially those who started with lesser strength, saw a notable rise in the thickness of their bicep muscles when measured against the control group and achieved results on par with those who took whey protein. 

Supporting Athletic Performance

Soy Protein Powder

A systematic review of 19 randomised controlled trials concluded that supplementing with soy protein powder can improve performance in high-intensity and high-speed running, increase maximal cardiac output, extend time to fatigue, enhance isometric muscle strength, improve endurance among amateur cyclists, and lower lactate accumulation (7).

A sample of soy protein isolate. These cost about a pound 

Pea Protein Powder

An investigation published in Sports (8) explored how whey and pea protein supplements impact strength in men and women undergoing an 8-week regimen of high-intensity functional training (HIFT), with participants consuming 24 grams of either protein type on training and non-training days. Both pea and whey protein groups showed significant increases in strength, as measured by 1-rep max for back squats and deadlifts, suggesting that pea protein is as effective as whey protein for enhancing strength

You might also like my articles comparing pea, soy, and whey protein and comparing pea and whey protein

Supporting Weight Loss

Soy Protein Powder

In one randomised, controlled study (9), 90 overweight and obese participants were divided into three groups to test the effects of lifestyle education alone (LE-G), a high-soy-protein, low-fat diet (SD-G), and the same diet with guided physical activity (SD/PA-G) on body composition. The results showed significant weight and fat mass loss in the groups consuming soy protein, either with or without exercise, compared to the lifestyle education group, without substantial loss in lean body mass. 

Pea Protein Powder

A study published in Current Developments in Nutrition (10) provides evidence that pea proteins can minimise appetite, so they may be beneficial for those looking to decrease their caloric intake and weight. 

Other Health Benefits

As well as positively influencing athletic outcomes, soy and pea proteins may have effects that benefit overall health...

Blood Pressure

Both soy and pea protein powders have been linked to reduced blood pressure (11, 12). 

Blood Sugar

There's evidence that soy and pea proteins could help maintain healthy blood sugar levels (13, 14). If you're interested in this topic, you might like to check out my article on the best protein supplements for those with diabetes

Cholesterol

Studies suggest that soy protein and pea protein may help lower cholesterol levels (15, 16). 

Breast Cancer

A meta-analysis published in the British Journal of Cancer found that soy consumption was unrelated to breast cancer risk in Western populations and was associated with a lower risk in Asian populations (17).

Food Allergies

Four in every thousand children will have an allergic reaction to soy, though 50% develop tolerance to this common allergen by the time they're seven years old (18). Soy allergy symptoms range from mild to severe and include hives, itching, eczema, tingling in the mouth, swelling of various body parts, breathing difficulties, gastrointestinal distress, dizziness, and, in serious cases, anaphylaxis, a potentially life-threatening reaction. As suggested below, if you suspect you may have an intolerance to soy, you could try out one of the other plant-based options mentioned. 

Environmental Impact

While the production of plant-based proteins tends to have a lower environmental impact than the production of animal-based protein sources (19), there are differences between plant-based protein sources. For example, pea production is estimated to have a lower potential effect on climate change than soy production (20) and typically requires less water

Other Plant-Based Proteins

If you're concerned about soy allergies, there are various other powders suitable for plant-based diets that you could consider, including hemp protein and rice protein powders as well as vegan blends. 

Table 2. Calories and Grams of Macronutrients per 100 Grams in Hemp, Rice, and Vegan Blend Protein Powders From Myprotein (MP) and Bodybuilding Warehouse (BW)

SupplementCaloriesProteinCarbsFats
Pure Hemp 504064716.013.0
MP Rice Protein Powder423783.82.1
MP Vegan Protein Blend3667111.02.5
BW Vegan Blend337716.52.5

Comparing the protein column in this table to the one in the previous table, you can see that these vegan protein powders, especially the one made from hemp seeds, have a little less protein than the pea and soy protein powders. However, it's only a small difference, and these plant protein sources could still make reaching your protein targets much easier. 

My vegan blend sample from Myprotein. At the moment, you can pick up a sample like this for less than a pound. 

You might also like my articles comparing brown rice and whey protein powders, hemp and pea protein powders, and rice and pea protein powders

Other High-Protein Food Products for Those on a Vegan Diet

If you're not keen on protein powders, you could also aim to increase your protein intake through plant-based meat products. For example, Muscle Food has a soy-based bolognese, a soy-based "chicken" pot, and other soy products. If you'd prefer something sweet, you could also check out the plant-based snacks offered by Myprotein. For those after pea protein products specifically, as the name suggests, the Pea-Nut Square combines pea and nut proteins. 

Table 3. Comparison of Myprotein's Plant-Based Protein Snacks With Respect to Their Calories and Macronutrients

SnackCalories per 100gProtein (g per 100g)Carbs (g per 100g)Fats (g per 100g)
Vegan Carb Crusher394273117
Pea-Nut Square466242727
Vegan Double Dough Brownie403214215
Vegan Gooey Filled Cookie330184911

Out of these, I've so far only tried the Vegan Carb Crusher, which is chewy but also has a bit of a crunch. You can get a sample on Myprotein for very little, which could be worth doing to see if you like it before committing to a box. 

The Vegan Carb Crusher I tried. I don't usually have snacks like this as part of my normal diet as I prefer protein powders since they have more protein per calorie. However, this type of thing is great when you're travelling and don't want to carry around bags of protein powder and a shaker. 

If you want less processed food sources, you could just eat peas or soy beans. 

The peas in my freezer contain 6 grams of protein, 11 grams of carbohydrates, 0.4 grams of fat, and 84 calories for every 100 grams. This translates to a cup of peas (165 grams) providing 9.9 grams of protein, 18.2 grams of carbohydrates, 0.7 grams of fat, and 138.6 calories. So, to match the protein content found in one scoop of pea protein isolate, you would need approximately two and a half cups of peas. However, while having less protein, the nutritional profile of peas is superior to that of pea protein isolate as they contain various micronutrients (e.g., magnesium, iron; 21) that tend to be lost when turned into powder. 

Wikipedia's page dedicated to soy beans indicates that they contain substantially more protein than peas, so you wouldn't need to eat so many to match the amount of protein you get in a scoop of soy protein powder. 

Conclusion

For those looking for protein powders without animal-based proteins due to environmental concerns or other reasons, soy and pea protein powders are both excellent options. In terms of their amino acid content, both provide all essential amino acids and have a decent amount of those linked to positive athletic outcomes (e.g., leucine). If you've ever experienced digestive discomfort after consuming soy milk or other soy-based products, a pea protein powder may be the better option. 

You might also like my article comparing protein powders and bars or my article comparing plant and whey proteins for bodybuilding

About the Author

Dave Robinson, a co-founder of ukfitness.pro, has a background in psychology (BSc) and neuroscience (MSc, PhD). As well as strength training, he enjoys endurance challenges and has run ultramarathons, cycled across several countries, and completed the Three Peaks Challenge. When writing, he draws on scientific evidence to understand the pros and cons of different diets, supplements, and training regimes. 

The author riding a bike

References

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21. Hacisalihoglu, G., Beisel, N. S., & Settles, A. M. (2021). Characterization of pea seed nutritional value within a diverse population of Pisum sativum. PloS one, 16(11), e0259565. https://doi.org/10.1371/journal.pone.0259565