Soy Vs Whey Protein: Which Is Healthiest, And Most Effective? 

Last Updated:

Our diet and nutrition resources are rigorously vetted by our expert team and adhere to our Diet and Nutrition Guidelines.

Protein is necessary to build muscle and can help increase satiety and thus support weight loss, which is why protein powders are popular for weight loss and muscle growth.

With all of the different types of protein powders out there to choose from, it can be a bit overwhelming when deciding which one to use. Today, we will look at the difference between two popular protein powders, soy, and whey.

But, when looking at soy vs whey protein powder, which is better? Keep reading to learn about the pros and cons of soy vs whey protein powder.

In this guide, we will cover: 

  • How Are Soy and Whey Protein Powders Made?
  • Differences Between Soy vs Whey Protein
  • Benefits of Whey vs Soy Protein
  • Benefits of Soy vs Whey Protein

Let’s get started!

A person scooping protein into a shaker.

How Are Soy and Whey Protein Powders Made?

Soy Protein

Soy protein is a plant-based protein made from soybeans that have been ground into a meal. The soybean meal is defatted and does not contain the hulls of the soybeans. It is then further processed into soy isolate, which is about 90-95% protein.

The resultant soy protein powder is a complete source of protein, which means that it contains all nine essential amino acids.

Whey Protein

Whey protein powder is made from cow’s milk through a similar isolation process.

As soy protein isolate, whey protein isolate is about 90 to 95% protein by weight and is also a source of complete protein with all nine essential amino acids.

However, the amino acid profile in whey protein vs soy protein is different.

Due to these differences, whey protein powder is often thought to be superior to soy protein powder for athletic performance, muscle growth, and weight loss because there are more branched-chain amino acids (BCAAs) in whey vs soy protein powders.

Most whey and soy protein powders also have additional ingredients added to improve the texture and taste, such as cocoa powder, sweeteners, and additional nutrients.

A handful of soy protein.

Differences Between Soy vs Whey Protein

Soy Protein vs Whey Protein: Amino Acid Profiles

One of the primary differences between soy protein vs whey protein powders is in the amino acid profile offered by each product.

Although both soy protein powder and whey protein powder are complete proteins, the relative proportion of each amino acid differs.

The differences in the relative concentration of each amino acid are what are thought to confer some of the potential benefits of whey vs soy protein.

Soy protein is particularly high in arginine, tryptophan, and phenylamine.

Whey protein contains the highest percentage of essential amino acids. Moreover, whey protein is a particularly good source of branched-chain amino acids (BCAAs).

A scoop of protein powder.

Soy vs Whey Protein: Taste and Texture

Whey protein tends to be smoother because the powder is finer, so it dissolves more readily into water or whatever liquid you are using. Soy protein can be somewhat gritty. 

One thing to note with whey protein is that with whey protein powders that are made from whey concentrate, the percentage of lactose in the product is higher than in whey protein powders that are made from whey protein isolate. 

Another thing to note is that although whey protein isolate can mix into a very smooth and relatively neutral protein shake, whey protein concentrate, as it is less processed, may be somewhat chalky.

In terms of taste, the majority of protein powders are flavored or further processed in some way to improve taste and texture.

Therefore, you can get a delicious chocolate soy protein powder or creamy vanilla whey protein powder, or any number of other flavors and combinations.

With that said, with unflavored protein powder, you will typically get a more neutral flavor with whey vs soy protein powder. 

Soy protein powder has a stronger nutty flavor. Some people enjoy this rather than having a completely neutral product, but it is something you will want to consider.

A tub and scoop of protein powder.

Whey vs Soy Protein Powder: Nutrition

In addition to the protein content found in each of these protein supplements, there can be differences in the nutritional profile between soy vs whey protein powders.

Many protein powder supplements have added nutrients to round out the nutritional profile, but soy protein is a natural source of all of the B vitamins, zinc, iron, phosphorus, magnesium, potassium, and vitamin E. 

Whey protein powder usually contains calcium, potassium, magnesium, and phosphorus.

Benefits of Soy vs Whey Protein

There are benefits to both whey protein and soy protein.

Here are some of the top benefits of soy vs whey protein powder:

Soy Protein Powder Is a Plant-Based Protein Powder

The primary reason that most people choose to have soy vs whey protein powder is that soy protein is a plant-based protein powder, whereas whey protein is not.

If you are following a vegan diet, you will need to choose soy vs whey protein, as whey protein powder is made from cow’s milk.

Even if you are not following a plant-based diet specifically, many people have a sensitivity to lactose or dairy and may find that they have digestive issues with whey protein powder.

If you have tried whey protein powder in the past and have found that it made you bloated, gassy, or caused an upset stomach, consider trying soy protein powder because you might have been reacting to the dairy in whey protein.

A scoop and bowl of soy protein.

Benefits of Whey vs Soy Protein

There are several notable benefits of whey vs soy protein powder:

Whey Protein Powder Has Greater Bioavailability 

One of the benefits of choosing whey protein vs soy protein powder is that way protein has the highest biological value (BV) of any of the common protein sources used in protein powders.

The BV of whey is 104, whereas the BV of soy protein is 74. The biological value of a protein doesn’t fully reflect how much is actually digested and absorbed. 

The higher biological value of whey vs soy protein means that your body is able to make use of the protein found in whey protein powders more quickly and effectively after ingestion.

For this reason, it is often better to have whey protein vs soy protein powder supplements after a workout to facilitate rapid post-workout recovery.

However, although the bioavailability and absorption are better in whey vs soy protein, both forms of protein have a Protein Digestibility Corrected Amino Acid Score of 1.00

This means that the limiting essential amino acid (the amino acid in the lowest concentration) still satisfies 100% of the requirements of that essential amino acid, according to the Food & Agriculture Organization and World Health Organization.

This is why both whey and soy are considered complete proteins.

A woman drinking a protein shake.

Whey vs Soy Protein for Weight Loss

Most studies have found that whey protein is better than soy protein in terms of promoting weight loss and fat loss.

For example, in one study, whey protein resulted in significantly more total weight loss and body fat loss than soy protein.

The study followed men with obesity who were split into three groups, a group that consumes 56 g per day of whey protein, a group that consumes 56 g per day of soy protein, and a group that consumed the same number of grams of a carbohydrate substance every day.

After 23 weeks, only the whey protein group lost significant total weight and body fat (2.3 kilograms of body weight and 1.8 kg of body fat). Waist circumference also decreased significantly in the whey protein group, indicating a decrease in belly fat.

In contrast, the soy protein group and the carbohydrate group did not lose a significant amount of weight or body fat.

A muscular man shaking up a protein shake.

Whey vs Soy Protein for Muscle Growth

In terms of muscle building, one study compared the rate of muscle protein synthesis (the physiological process underpinning muscle growth) between whey protein vs soy protein vs casein protein.

Results suggested that at rest, muscle protein synthesis was greatest in whey protein, followed by soy protein, followed by casein protein.

The differences in muscle protein synthesis rates were even more pronounced between whey vs soy protein (and trailing casein) after weightlifting workouts.

The researchers concluded that whey protein is more effective at stimulating muscle growth than soy protein or casein protein. 

Another study essentially corroborated these results, taking it one step further by demonstrating that consuming whey proteins indeed resulted in more muscle growth than consuming soy protein.

Two scoops of vanilla protein powder.

After nine months, the subjects who had consumed whey protein gained almost twice as much lean body mass than those consuming soy, with an average increase of 3.3 kg of lean body mass for those consuming whey protein versus an increase of 1.8 kg of lean body mass with soy protein.

However, other studies have found that as long as the protein powders provide a similar number of grams of total protein and BCAAs per serving, whey, and soy protein powders are equally effective at building muscle or promoting muscle hypertrophy.

Evidence also suggests that strength gains can be similar when consuming soy protein or whey protein powders as long as the protein powders provide a similar amino acid profile.

So, after reviewing all of the information, which protein is best for your needs?

If you are looking for some protein powder recipes, check out our guide: Here are 7 Great Protein Powder Recipes That Aren’t Shakes!

Protein powders and a shaker.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.