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Is Soy Protein as Good as Animal Protein?

By: by Amino Science
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Protein makes up virtually every part of your body—skin, hair, muscle, and bone. It charges chemical reactions and the hemoglobin that carries oxygen in your blood. You are made up of at least 10,000 different proteins, and your body requires replenishment of this macronutrient each and every day. 

But protein varies wildly on the spectrum of quality, and plant-based proteins such as pea, hemp, and soy, have a reputation for being not as good as animal-based proteins such as meat, dairy, and eggs. Without vilifying either animal or plant protein, we’re giving a scientific assessment of the question: Is soy protein as good as animal protein?

The Protein Package

In order to understand the differences between soy protein and animal protein, it’s helpful to have an understanding of what makes a protein. 

Protein is made up of unique combinations of 20 different amino acids linked together in a chain. When we eat dietary protein, the body immediately gets to work breaking the protein chain apart into its individual amino acid components so that each amino can go about its business in the body.

Of the 20 amino acids in the human body, 11 are nonessential amino acids that the body can produce in-house, while the other 9 are essential amino acids that we can only get from food (or supplementation, which we will talk about later).

When pitting vegetable protein against animal protein it all comes down to the essential amino acids that make up the protein content:

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

Which protein type, animal or soy, has the best essential amino acid profile, is the easiest to digest, and is the most bioavailable? Let’s find out.

Assessing Protein

When nutrition researchers look at the quality of protein they look specifically at the amino acid composition of a protein and the protein’s ability to be digested, absorbed, and maintained by the body. 

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is used to measure protein quality. A protein that scores less than 100% on the PDCAAS does not meet the body’s essential amino acid requirements. Apart from soy protein isolate, no plant-based protein makes the cut. Take a look at the chart below sourced from a meta-analysis in the journal Nutrients.

Protein quality score of soy protein

In 2013, the FAO Expert Consultation on Dietary Protein Quality Evaluation added a second protein quality score called the Digestible Indispensable Amino Acid Score (DIAAS), which measures protein quality based on each individual amino acid in a protein. According to the DIAAS, no plant-based protein source, including high-protein soybeans, makes it to the 100% mark. 

When it comes to the quality of the protein, animal protein is the winner. But that doesn’t mean soy protein is not as good overall, as it offers many health benefits.

When Protein Quality Suffers, So Do Your Muscles

A cup of cow's milk has 8 grams of milk protein and a cup of soy milk has 8 grams of soy protein. The same amount of protein, however, does not equate to the same amount of muscle gain. 

The main issue with soy protein is that it does not have the anabolic (muscle-building) capacity that animal proteins do. Soy protein is also not as digestible or bioavailable, and has a lower amino acid content overall. 

Do a quick Google search and you’ll see the health claim that soy is a complete protein. Amino Company scientists are a little more cautious in their assessment of the amino acid profile of soy. While it has all nine essential amino acids, it has limiting amounts of methionine and lysine, which impairs its anabolic effects. 

If you are looking to protein to stimulate muscle growth and build lean muscle mass and strength (and you should be!), then soy protein isn’t the dietary protein to count on. You'd be better off with whey protein or casein food products.  Animal protein, or supplementing with a vegetarian or vegan essential amino acid supplement are even better options (1).

That being said, soy protein does indeed come with wellness gains and shouldn't be written off for good.

Health Benefits of Soy Protein

Soy protein comes from whole soybeans, a cholesterol-free and saturated fat-free legume with very little carbohydrates. While red meat, particularly the processed kind, has been implicated in increased risks of coronary heart disease, type 2 diabetes, and cancer, soy protein is linked to lower triglyceride and LDL cholesterol levels (due to phytoestrogens), weight loss, better blood sugar control, and a lower risk for chronic disease.

Soy protein also contains substantial amounts of calcium, iron, potassium, magnesium, dietary fiber, and zinc

Eating a variety of dietary proteins that include both plant and animal protein sources ensures you’re meeting your nutrient needs on all counts. 

The Best Soy Foods 

Just like processed meat isn’t the healthiest, processed soy products like soy burgers and soy sauce are likewise not the healthiest choice you could make.

Soy products, like protein powders and nutrition bars, are made from soy protein concentrate, with soy protein isolate and textured soy protein that contains soy isoflavones that mimic the effects of estrogen in the body and can have unwanted side effects. It's a delicate balance, as phytoestrogens in soy are also being studied to help prevent bone loss and hot flashes in women going through menopause.

According to the U.S. Food and Drug Administration (FDA), genistein, a phytochemical in soy, is showing promise as an anti-cancer agent for both breast cancer and prostate cancer, as it helps prevent tumors from developing blood vessels that would promote proliferation and metastasis.

The beneficial effects of soy protein are found in whole soy products:

  • Edamame
  • Soy milk
  • Tofu
  • Tempeh
  • Soy nuts
  • Soy flour
  • Cooked soybeans 
  • Miso
  • Natto (fermented soybeans)

Supplementation Tips

In a perfect world and with a perfect diet, you’d get all the protein you need. Unfortunately, conditions and diets are far from perfect. 

For instance, as we age, our muscles become less responsive to the muscle-building signals of protein. We need to eat even more high-quality complete proteins to get muscle protein synthesis going. This can be challenging, especially if our appetites aren’t as big as they once were, or we are ill or stressed, which increases our need for protein even more.

Vegetarians and vegans also have a difficult time meeting their protein needs since, as we have discovered, the quality of vegetarian protein foods just isn’t as complete.

In circumstances such as these, supplementation becomes our saving grace. 

Supplementing with an essential amino acid supplement is the best way to increase your protein intake, particularly because it won’t compromise your diet goals or go against your dietary restrictions.

Amino Co essential amino acid powders are:

  • Vegetarian or vegan
  • Gluten free
  • Soy free
  • GMO free
  • Halal 

Our patented protein products are designed to build lean muscle mass, increase energy and endurance, promote cardiovascular health and decrease the risk of heart disease, support a healthy lipid profile, and accelerate muscle recovery and wound healing. You can shop our line of essential amino acid blends for your specific health needs here.

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