Soy Protein Vs. Whey Protein: Everything You Need To Know

Let’s look at soy protein and whey protein, and everything you want to know about them. Plus get into a delicious açai protein smoothie bowl recipe full of nutrients and of course, a huge kick of protein. 

What Is Protein?

Firstly, do you know what protein is? Protein is one of the major macronutrients, along with fats and carbohydrates that we consume in large amounts from the food we eat. Protein chiefly is responsible for supporting growth, development and immune function. Protein is an essential component of any healthy diet. A protein molecule consists of individual chains of amino acids. 

There are 20 standard amino acids that form the building blocks to make important compounds in the body. There are 10 essential amino acids that our body needs to function, which must be obtained from the food we eat. The other non-essential amino acids can be made in the body from the essential amino acids. Muscle cells and neurotransmitters like dopamine are made from amino acids. Enzymes and hormones are also synthesised from proteins and amino acids. 

It’s easy to see that without enough protein, your brain doesn’t work as well, and neither does your body.

So, how do we make sure we’re getting enough protein from food? 

Food Sources of Protein

The obvious food sources will be meat, like beef, lamb, pork, chicken, seafood and eggs. Dairy products like cheese, milk and yoghurt also qualify as decent protein sources. What about vegetarian or vegan protein sources? Nuts and seeds like almonds, peanuts, and tahini are great options. Hemp seeds and tofu/soybeans rank highly due to their amino acid profile. Other legumes are up there as well in terms of protein content. 

Some nutrition experts will argue that plant sources of protein are not as bioavailable as animal sources. This appears to be true for soy vs. whey protein powders. This means that the proteins found in plants, legumes and vegetables are more difficult to digest in the body, compared to meat. If possible, it’s best to obtain protein in the diet from a mix of veggies and meat sources to ensure optimal intake. 

Are Protein Powders Beneficial? 

However, for many of us, this isn’t always achievable. This is where protein powders can be helpful. I like to utilise protein powders in healthy smoothies, in cases of frank protein deficiency or in periods of increased demand. For example, protein powders can be useful during acute or chronic illness, during intense exercise or even during pregnancy and breastfeeding. Boosting your protein intake can make a marked difference to your energy levels and immune system. Let’s now compare two of the most popular protein powders available: soy and whey protein.

What Are Soy Protein & Whey Protein?

Understanding the differences between soy protein and whey protein can help you make the right choice for your body. Here we’ll define each and take a look at the benefits and drawbacks of both protein powder types. 

Soy Protein

Soy protein has been around since the 1960s as a food substance. It’s made from soybeans, which are legumes that are naturally high in protein. Soy protein is manufactured from soybeans that have been ground into a meal, and then further processed into a soy protein isolate. This product is then marketed as soy protein and consists of around 90% pure protein. It’s a good choice for vegans or vegetarians, as it’s entirely plant-based. Soy protein powder can be used to make a protein shake, protein smoothie or be added to soups or sauces. The texture is slightly grainy and needs to be blended well before being consumed. Make sure you’re reading the labels on soy protein isolates. Commonly, additives are included to improve taste and texture.

Whey Protein

Whey protein is made from cow’s milk. The natural composition of milk is around 3.5% protein and 4% fat, plus some water, vitamins and minerals. Whey protein is manufactured as a side-step from how cheese is made. Firstly, cow’s milk is pasteurised and enzymes are added to the milk to separate the milk solids from the whey. It undergoes a further processing step to remove carbohydrates and water, resulting in a protein powder known as whey protein isolate or WPI. As a protein supplement, whey is easily digestible and has a wealth of health benefits to support its use. However, it won’t be suitable for vegetarians or vegans as it’s derived from an animal source.

What to Consider When Choosing Soy & Whey Protein

Taste & Texture

Whey protein is typically smoother, and has a mild creamy and nutty taste. It’s great in smoothies and homemade ice blocks for this reason. Soy protein, however, has a more obvious nutty flavour and a slightly grainier texture. Many products are marketed with different flavours or have emulsifiers, thickening agents or other additives. Ideally, it’s best to source a top-quality, ‘clean’ protein powder, with the least amount of synthetic ingredients possible. The caveat to this would be some protein powders have natural substances for added health benefits, like green tea extract, which is fine to consume. 

Amino Acid Composition

In general, for a protein powder to call itself one, it needs to consist of a complete amino acid profile. This means that all 20 amino acids will be listed in the ingredients. Or, at the very least, the essential amino acids. Luckily, both soy and whey protein are considered ‘complete’ proteins because they contain the essential amino acids naturally. The differences lie in how much of each amino acid both protein powders possess. For example, whey is usually higher in leucine, isoleucine, methionine and lysine. These compounds are required for muscle growth, which makes WPI a popular choice for bodybuilding and exercise recovery. Comparatively, soy protein has high amounts of arginine, tryptophan and phenylalanine. Overall, both powders contain adequate amounts of essential and non-essential amino acids which support health in many ways.

Dietary Requirements

Soy protein is made from plants, while whey protein is made from cow’s milk. Upfront, if you’re vegetarian, you may opt to skip WPI and try soy protein to see if it works. If you suffer from milk protein allergy, whey protein may not be suitable. Importantly, pure WPI does not contain lactose, so it’s completely suitable for lactose-intolerant people. Whey concentrate protein powders typically still contain lactose. Just be sure to read the labels, with whatever you choose.

Soy & Whey Protein: Health Benefits

Is Whey Better Than Soy For Muscle Growth?

In truth, there is conflicting evidence in this field of health science as well. A randomised trial from 2020 revealed that there was no significant difference between soy and whey protein supplements once they were matched for leucine content. After 12 weeks of resistance training, three times per week coupled with matched amounts of 2g leucine intake, there was no difference between the soy protein and whey protein groups. A recent study published in The Journal of sports medicine and physical fitness confirmed a similar finding. Forbes and Bell (2020) found that compared to a placebo, whey protein and whey concentrate had no effect on muscle gain in a small group of athletes over six weeks. 

Yet, according to some recent research, whey protein is one of the highest-quality proteins, due to its digestibility and amino acid content. Compared to soy, whey protein has been found to stimulate muscle protein growth and development to a greater extent. While the evidence amongst clinical trials may be debatable, maintaining skeletal muscle mass is hugely important to health. Diets that are naturally high in all types of protein help promote gains in muscle mass, especially alongside resistance training.

Whey vs. Soy On Inflammation & Cancer Therapy

An interesting and very recent meta-analysis was published in The British Journal of nutrition. The review aimed to investigate the effects of WPI and soy proteins on inflammatory markers. Intriguingly, 31 trials conclusively found that both soy and whey protein supplementation caused anti-inflammatory effects by reducing inflammatory cytokines in tissues.

As found in a recent clinical trial, whey protein has protective effects on immunity and improved glutathione levels in a group of cancer patients. An important note in this study is that the test group received zinc and selenium along with 40g of WPI supplements for 12 weeks. This may indeed confound the findings, as these nutrients are strongly linked to better immune function. Nevertheless, patients receiving whey protein intervention had a greater overall nutritional status, while undergoing chemotherapy. 

Choose Your Protein Powder Adventure

The right protein powder for you is dependent on a myriad of factors. It’s a good idea to try out different protein powders and see what works best for your palate, budget and nutritional needs. If you’re feeling sluggish or bloated after trying a certain type, pay attention to your body and seek professional advice if you're in doubt.