Is Soy Protein Isolate Bad For You? The Answers You’re Looking For

Let's delve into the debate surrounding soy protein isolate, a common ingredient in vegan and vegetarian foods. We investigate its nutritional value, potential health benefits, and concerns. Also, we compare it with other protein sources and suggest healthier alternatives. Discover if soy protein isolate is right for your diet as we advocate for a journey towards optimal plant-based health.

Isabelle Sadler
May 19, 2023

As plant-based diets grow in popularity, one ingredient you might frequently encounter is protein isolates, particularly soy protein isolates. 

Often found in protein bars, soy protein powders, and meat substitutes, it provides a convenient, high protein alternative for vegetarians, vegans, and those reducing meat intake. 

Yet, we often hear the question, "Is soy protein isolate bad for you?" 

Let’s delve into this topic and get some answers. 

Understanding Soy Protein Isolate

Soy protein isolate is a highly refined form of soy protein with about 90% protein content. 

It’s created by removing most of the fat, fiber, and carbohydrates from soy, leaving primarily protein, and processing it into flake form 1

This high concentration distinguishes it from soy protein concentrate, which has about 70% protein and more fiber than soy protein isolate.

Soy protein isolate is found in many plant-based protein alternatives, with pea protein isolate emerging as a popular contender in bars, protein powders, and meat substitutes. 

Is Soy Protein Isolate Bad for You?

There's considerable debate surrounding the health effects of soy protein isolate. 

On one side, it's lauded as a high-quality protein source, rich in all essential amino acids 2. Yet, critics argue that soy isolate processing could affect the protein's natural structure and potentially diminish its nutritional value.

Notably,  research suggests that plant proteins, including isolates, can lower LDL cholesterol levels. A study found no significant difference in cholesterol-lowering effects between whole plant foods and protein isolates, indicating that soy protein isolate may also offer this health benefit. 3. Nevertheless, these results require further confirmation.

However, it's important to remember that the health value of soy protein often depends on the ingredients with which it’s combined. 

For instance, ingredients like added sugars, saturated fats, or artificial additives in soy protein powders or meat substitutes can pose health risks, often more than the soy protein isolate itself.

Other ingredients that can be added to soy protein isolate foods include: 

  • Coconut oil
  • Canola oil 
  • Flavor enhancers
  • Binders
  • Stabilizers
  • Thickeners, like methylcellulose 
  • Preservatives
  • Sugar
  • Sweeteners

The high sodium content in soy protein and pea protein meat substitutes like Beyond Meat Burger and Impossible Burger can also raise concerns, particularly for those with high blood pressure or kidney disease. The Impossible Burger contains 370 mg of sodium, and the Beyond Meat Burger contains 390 mg — that’s nearly 20% of the recommended sodium limit in just one burger, and represents a higher percentage for those who need to keep their sodium intake low. 

Another area of concern is the potential contamination of soy and pea protein powders with traces of harmful substances including heavy metals, bisphenol-A (BPA, which is used to make plastic), pesticides, or other contaminants with links to cancer and other health conditions. These impurities, which may be absorbed from the soil during plant growth, can become concentrated in the protein powder. It could also be due to the manufacturing process, according to the Clean Label Project who initially reported the findings.

While the levels found in most products are generally below established safety limits, opting for rigorously tested brands or whole, unprocessed foods can offer a safer option.

Soy Protein Isolate vs. Other Protein Sources

The healthiness of soy protein isolate depends on what it replaces in your diet. While it provides high protein content, its highly processed nature means it lacks the nutrients found in whole plant foods. 

Compared to whole plant foods like tofu or legumes, soy protein isolate is less healthy, owing to its reduced nutrient content and the addition of saturated fats, sugars, and sodium in products. This is often because of what soy protein isolate is paired with to make a product, not the soy protein isolate itself. Whole plant foods contain fiber, vitamins and minerals, essential fatty acids, and phytonutrients, all of which are very beneficial to our health.

However, when comparing a plant-based protein isolate to animal protein, they can often be seen as healthier.

One study involving 38 people, found that replacing two servings of animal protein per day with plant-based meat alternatives resulted in improved markers of cardiovascular disease risk 4. The study did have its limitations, such as a short duration, small sample size, differences in nutrient content between the plant and animal meats, and the fact that it was funded by a plant-based meat company. This could have affected the outcome, so more research is needed in this area.

Also, plant protein intake compared to animal protein intake is associated with a lower risk of dying from all causes put together, such as from diseases like cancer and heart disease 5.  

Compared to something like a processed meat sausage, we can say the soy protein option is the better option, as processed meats are known to be a cause of cancer

Therefore, if you’re trying to reduce your intake of animal-based foods, but aren’t ready to go completely focused on whole foods all the time, soy protein isolates can be a viable option. 

Alternative Protein Options

If you're seeking alternatives to soy protein isolate or concentrate, consider whole plant foods like tofu, legumes, quinoa, seeds, and nuts. Choosing these whole foods provides not only protein, but additional health benefits like fiber, vitamins, and minerals, making them a superior choice for long-term health.

I’ve even seen people make protein smoothies by blending cooked black beans and/or silken tofu with frozen banana, cacao powder, dates, and water to make a delicious-looking protein-packed smoothie without the processed protein powder. 

If you’re looking for a protein powder alternative, maybe that’s worth a try! 

Remember, not all soy protein isolate products are made equal. If a soy or pea protein burger is going to be added into your diet every once in a while, choose those that have fewer added ingredients. A good rule of thumb is to go for the one with ingredients that you recognize the name of, or can at least pronounce! 

Another option is to opt for plant-based burgers that have been made from black beans, mushrooms, or whole grains. You can find varieties that have fewer additives and more whole ingredients. If time allows, these can also be homemade! 

The Bottom Line

So, is soy protein isolate bad for you? It depends on various factors, including the quality of other ingredients in the product 

While soy protein and its derivatives can serve a role in transitional diets or specific nutritional needs, at Mora Medical, we advocate for whole plant foods as the optimal choice for your health. 

Remember that variety is vital in your diet. Always strive to incorporate a diverse range of whole foods into your meals. It's about fueling your body in a way that aligns with your health objectives and nourishing your journey towards optimal, plant-based health.


1. Karki, B. et al. Functional Properties of Soy Protein Isolates Produced from Ultrasonicated Defatted Soy Flakes. J. Am. Oil Chem. Soc. 86, 1021–1028 (2009).

2. Michelfelder, A. J. Soy: a complete source of protein. Am. Fam. Physician 79, 43–47 (2009).

3. Li, S. S. et al. Effect of Plant Protein on Blood Lipids: A Systematic Review and Meta‐Analysis of Randomized Controlled Trials. J. Am. Heart Assoc. 6, e006659 (2017).

4. Crimarco, A. et al. A randomized crossover trial on the effect of plant-based compared with animal-based meat on trimethylamine-N-oxide and cardiovascular disease risk factors in generally healthy adults: Study With Appetizing Plantfood—Meat Eating Alternative Trial (SWAP-MEAT). Am. J. Clin. Nutr. 112, 1188–1199 (2020).

5. Budhathoki, S. et al. Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality in a Japanese Cohort. JAMA Intern. Med. 179, 1509 (2019).

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