The Ultimate Guide to Soy Protein Isolate and Other Forms of Soy Protein

Soy protein has become an incredibly popular plant-based protein source for vegans, vegetarians, and flexitarians. With rising interest in plant-centric diets and concerns over sustainability and health, understanding the various types of soy protein is key.

What is Soy Protein Isolate?

Soy protein isolate is a highly refined type of protein powder made from dehulled soybean flakes. It contains at least 90% protein by weight, giving it the highest concentration of protein of any soy product.

During processing, the soy flakes first undergo solubilization and separation to remove fiber and other carbohydrates. This leaves a concentrated soy protein solution which then goes through an isolation process to remove fats, minerals, and moisture. What remains is an extremely pure, nearly flavorless powder that is around 95% protein by content.

Thanks to the extensive processing it undergoes, isolated soy protein has an exceptionally neutral taste compared to other soy-based foods like tofu or edamame. It readily absorbs flavors from other ingredients, making it very versatile to cook with. The high protein concentration also makes it useful for boosting the protein content of shakes, smoothies, energy bars, cereals, baked goods, and more.

Benefits of Soy Protein Isolate

High Protein ContentSoy protein isolate typically contains around 90% protein, making it a concentrated vegetarian protein source.
Lean Source of ProteinSoy protein is low in saturated fat and contains no cholesterol compared to animal protein sources.
Rich in BCAAsSoy protein contains high levels of branched-chain amino acids (BCAAs) like leucine, which help stimulate muscle protein synthesis.
May Reduce Heart Disease RiskSoy protein has been associated with reduced LDL “bad” cholesterol levels, which may lower risk of cardiovascular disease.
Promotes Muscle GrowthThe high leucine content of soy protein isolate may help increase muscle mass, especially when combined with strength training.
Supports Weight LossReplacing higher-calorie protein sources with soy protein isolate can facilitate fat loss while maintaining lean muscle mass.
Easy to DigestSince most of the indigestible carbohydrates have been removed, soy protein isolate is usually easily digested and less likely to cause gas or bloating.

Soy protein isolate offers several advantages:

  • Highly Digestible: The isolation process makes the protein easier to break down and absorb during digestion. Studies show the digestibility values of soy protein isolate range from 88-98% depending on preparation methods.
  • Very Low Fat and Carbs: With almost all fat and carbs removed, soy protein isolate provides protein in its purest possible form. Each 30-gram serving provides about 25-28 grams of protein with minimal fat, carbs, and calories.
  • Supports Muscle Growth: Like other complete proteins, soy protein isolate contains all the essential amino acids needed to maintain and build muscle. Numerous studies show supplementing with it can boost strength and muscle mass gains from resistance training.
  • Plant-Based: Soy beans are naturally cholesterol-free. Soy protein isolate is vegan and vegetarian-friendly, allowing people to avoid meat to meet their protein needs.
  • Gluten-Free: Soy protein isolate is safely consumed by those sensitive to gluten. Look for varieties that are certified gluten-free if this is a concern.
  • Non-GMO Available: Soybeans are predominantly GMO in the USA. Seek certified non-GMO soy protein isolate if wishing to avoid genetically engineered soy.
  • Sustainable: Soybeans require fewer resources to grow than most other protein-rich crops. Choosing soybean products like isolates has less environmental impact than many animal proteins.

Common Types of Soy Protein

Soy Protein IsolateContains 90-95% protein; made by removing fiber and carbs from defatted soybeansProtein powders, protein bars, meat alternatives
Soy Protein ConcentrateContains 70-80% protein; made by removing some fiber and carbsVegetables, snacks, salads, stir-fries
Textured Soy Protein (TSP)Defatted soy flour processed into granules, chunks, or flakesMeat extenders, vegetarian burger patties, chili
Soy FlourGround soybeans into a fine powder; 40-50% proteinBaking, smoothies, pasta, bread
Soy MilkLiquid made from soaked, ground, and strained soybeansBeverage, smoothies, cereal, or can be processed into tofu
EdamameWhole soybeans, harvested when nearly ripePlant-based meat substitute can be fried, baked, or sautéed
TofuSoy milk curdled into soft white blocksMeat substitute, a source of probiotics, used in stir-fries and sandwiches
TempehCooked, fermented whole soybeansPlant-based meat substitutes can be fried, baked, or sautéed

In addition to isolates, there are a few other common types of soy protein

Soya Chunks Protein

DescriptionDefatted soy flakes that have been compressed to form a chunky, meaty texture
Protein ContentTypically 52-55% protein per 100g serving
ManufacturingSoybean oil is extracted from soybeans, then the defatted flakes are moistened, extruded, and cut into chunks
TypesAvailable plain or preseasoned with flavors like chili garlic, curry, etc.
Benefits– High protein – Low fat – Takes on flavors of dishes – Meat substitute – Source of dietary fiber – Provides isoflavones
Uses– Curries, stir fries, and gravies – Soups, salads, and rice dishes – Kebabs, tikka masala, etc. – Hydrated in place of TVP chunks
PreparationUsually soaked in warm water to rehydrate before cooking to absorb sauces and seasonings.
StorageStore dried in an airtight container. Refrigerate once reconstituted.

Soya chunks (nutria) are pieces of compressed, dehydrated soy flour. They must be soaked in hot water or broth to rehydrate before cooking. Rehydrated soya chunks contain 11.5 grams of protein per 100-gram serving.

Soya chunks have a chewy, meaty texture and absorb surrounding flavors. They are a staple ingredient in vegetarian dishes, particularly in South Asian cuisine. They provide an easy, nutritious plant-based replacement for meat.

Soy Protein Concentrate

Soy protein concentrate contains 65-70% protein. It is made by removing a portion of the carbohydrates — mainly sugar molecules — from dehulled and defatted soybeans.

Retaining more fiber and nutrients than isolates gives soy protein concentrate greater nutritional value. It also maintains more of the characteristic bean-like flavor, which can be desirable in some recipes. Soy concentrates work well in blended meat products, nutritional bars, cereals, bakery items, and dairy alternatives.

Textured Soy Protein

Textured soy protein takes on a meat-like, chewy texture when hydrated and cooked. Forms like soy crumbles, granules, chunks, and strips absorb flavors and can mimic ground beef, chicken, pork, or other meats.

Textured soy protein contains approximately 50% protein by weight. As it retains more soybean nutrients and flavor, it is a hugely popular recipe ingredient for vegetarian and vegan dishes. It is also added to some meat products.

Hydrolyzed Soy Protein

Hydrolyzed soy protein consists of soy protein that has been broken down into smaller peptides for better solubility and amino acid absorption. The process uses enzymes and/or acids to “pre-digest” the proteins.

Bodybuilders favor hydrolyzed soy protein supplements as the peptides can be utilized for muscle protein synthesis more rapidly than intact proteins. However, evidence is mixed on whether hydrolyzed forms are truly more effective than regular soy protein powder for muscle gain.

Other Forms

There are also a variety of soy protein blends, soy flour, and products like soy nuts, soy milk protein, yogurts, cheeses, tofu, and more. Each has varying protein levels depending on preparation methods. For example, firm tofu blocks contain about 20 grams of protein per 100-gram serving.

Soy Protein vs Whey Protein

CategorySoy ProteinWhey Protein
SourceMade from soybeansMade from milk whey (liquid part of milk that separates from curds)
Protein ContentAround 50-90% protein depending on exact typeUsually 80-90% protein
Amino AcidsNot a complete protein – lacks sufficient methionine. But high in lysine.Complete protein – contains all essential amino acids. High in leucine.
Muscle BuildingDecent for building muscle due to high lysine. But absorption can be slower.Excellent for building muscle. Whey is quickly absorbed. Stimulates growth.
Weight LossGood for losing weight. Keeps you full. Not high calorie.Also good for losing weight by building and maintaining muscle tissue.
DigestionConsidered easily digestible by most people. Some get gas or bloating.Usually digested quickly and comfortably.
AllergiesGenerally not a common allergyOne of the more common food allergen triggers.
CostTypically more affordable than whey proteinOften costs more than soy protein
UsesProtein powders, bars, cereals, baked goods, meat substitutesMost popular in protein shakes and supplements

The two most popular protein supplements are soy and whey protein. But which is better? Here’s how they compare:

  • Amino Acid Profile: Whey protein has higher levels of branched-chain amino acids like leucine which are important for muscle protein production. Soy contains lower overall levels of BCAAs.
  • Leucine Content: Whey concentrates contain about 50-60% more leucine per serving compared to soy isolate. However, both are still quality complete proteins.
  • Digestion Rate: Whey protein isolate is considered the fastest-digesting protein powder, while soy isolate digests more moderately. Faster absorption can be beneficial post-workout.
  • Allergies/Intolerances: Whey is unsuitable for those with milk allergies or lactose intolerance. Soy should be avoided by those with soy allergies.
  • Taste and Mixability: Whey protein typically tastes better and mixes more smoothly than soy protein according to most consumers. However, unflavored soy isolate is relatively neutral tasting.
  • Cost: Soy protein powders tend to be significantly less expensive than whey protein. This makes it more economical, especially for daily use.

For most training goals, both soy-based supplements like isolated soy protein and whey protein supplements can support muscle growth. Those without allergies or food sensitivities may wish to consume a blend. However, whey has a slight edge for maximizing workout recovery and muscle gains.

Is Soy Protein Bad For You? Safety Concerns

Hormone Effects– Some studies link high soy intake to thyroid changes. But human data does not support these risks for those with healthy thyroids.
Thyroid Effects– Some studies link high soy intake to thyroid changes. However human data does not support these risks for those with healthy thyroids.
Digestive Issues– Soy can cause gas or bloating due to oligosaccharides. Usually is well-tolerated but some experience sensitivities.
Allergies– Soy is one of the 8 major allergenic foods. Allergy risk is low but possible, especially for young kids.
Nutrient Blocking– Theories that compounds in soy block nutrient absorption (minerals, protein, etc.) but robust human data does not substantiate these claims.
Cancer Risk– Isoflavones may act like estrogen, raising questions about hormonal cancer risk. However, most research shows soy does not increase cancer risk in humans.
Cognitive Issues– Some animal studies link high soy intake to cognitive decline. However, population studies show soy consumption may lower dementia risk.

Some people wrongly claim soy protein is bad for you due to misinformation about soybeans. However, all major regulatory bodies and nutritional organizations consider both whole soy foods and soy protein supplements safe.

Here are the facts regarding common soy protein concerns:

  • Hormone Effects: Early research raised uncertainty over soy’s effects on hormone levels in both men and women. However, two decades of extensive studies conclude that normal dietary soy intake — even fairly high levels — does not alter key sex hormones.
  • Thyroid Function: Goitrogens in raw soy can disrupt thyroid function if consumed in great excess. However, cooking and modern processing eliminate this concern. No evidence shows soy protein powder negatively impacts thyroid hormones.
  • Digestive Problems: As with most legumes, some individuals experience digestive discomfort from soy. While gassiness or bloating can occur, soy has fiber and oligosaccharides that may improve gut health for most people. Those with irritable bowel syndrome (IBS) should introduce soy cautiously.
  • Allergies: Like any food, soy can cause allergic reactions in those with soy sensitivities. This can usually be identified from a food allergy skin prick test or blood test. Thankfully soy allergies are far less common than many other allergens.
  • GMOs: There are no GMO safety issues verified by research. However, those wishing to avoid genetically engineered soy for personal reasons should choose organic, non-GMO-certified soy products.
  • Toxin Concerns: Raw soy can contain anti-nutrients like trypsin inhibitors that impact digestion and nutrient absorption. Modern processing methods eliminate any toxin concerns. No evidence demonstrates that processed, supplemental soy protein poses health risks.

Overall, decades of extensive research indicate that consuming normal amounts of soybeans, soy foods like tofu and tempeh, and soy protein supplements is perfectly safe for human health. Switching some dietary protein intake from animal to plant sources like processed soy offers significant health advantages.

Unless you have a known soy allergy or sensitivity, there is no reason to avoid supplementing your diet with quality soy protein isolate, textured soy protein, soy milk protein, or other bean-based protein products because of safety concerns.

Is Soy Protein a Complete Protein?

Yes, soy protein is considered a high-quality complete protein as it contains ample levels of all nine essential amino acids.

The amino acid profile of processed soy protein isolates and concentrates is particularly impressive. 100 grams provides comparable quantities of essential amino acids relative to common animal proteins.

Both the Food and Drug Administration (FDA) and the World Health Organization (WHO) recognize soy protein as equivalent to other high-quality proteins. As long as your diet provides sufficient energy and nutrients, soy protein can reliably meet all your body’s protein needs.

The Protein Digestibility Corrected Amino Acid Score (PDCAAS) is the gold standard for evaluating protein quality. Isolated soy protein ranks among the highest alongside casein, egg white protein, whey, and beef protein with a maximum PDCAAS score of 1.0.

Therefore, people do not need to combine soy protein with grains or other plant proteins. Consuming adequate soy protein in your diet is enough to maximize muscle growth and recovery.

Pea Protein vs Soy Protein

CategoryPea ProteinSoy Protein
SourceExtracted from yellow split peasExtracted from soybeans
Protein ContentTypically 80-90% proteinRanges from 50-90% depending on variety
Amino Acid ProfileLow in methionine, high in lysine so not a complete proteinAlso not a complete protein, low in methionine
AllergiesGenerally hypoallergenicSoy is one of the 8 major allergenic foods
DigestibilityVery easy to digest, less likely to cause gas/bloating issuesFairly easily digested but some experience gas/discomfort
EnvironmentRequires less water to grow pea plants than soybeansMost soy grown uses unsustainable farming practices
TasteNeutral flavor that takes on tastes of foods it’s incharacteristic “beany” flavor
CostOften more expensive than soy proteinTypically more affordable option
UsesProtein powders, shakes, bars, veggie meatsSimilar uses to pea protein as powders, meat substitutes

Alongside soy, pea protein is another popular plant-based supplement choice. Both are quality vegan protein options, but here’s how they differ:

  • Pea protein made from yellow split peas contains comparable protein content per serving to soy powders. However, PDCAAS scores show soy protein has a slightly higher quality amino acid balance.
  • Unflavored pea protein tends to have a more noticeable taste and gritty/chalky texture compared to neutral soy protein isolate. However, flavored pea proteins can taste quite good.
  • Clinical studies demonstrate soy protein isolate effectively supports muscle protein synthesis for both men and women. More long-term trials are needed for pea protein.
  • Since peas do not contain allergenic compounds found in soybeans, pea protein may be better tolerated by those with soy allergies. Cross-contamination is still possible though during manufacturing.

Both pea and soy protein make excellent vegan protein sources. Soy boasts a slight edge for muscle benefits according to existing research. Those sensitive to soy may wish to opt for a highly digestible pea protein isolate instead.

Recommended Intake

Most healthy adults should aim for a minimum of 0.8 grams of protein per kilogram of body weight daily to meet needs, per FDA guidelines. Active individuals or athletes require even more.

As long as your total daily protein intake from both whole food and supplements is adequate for your needs, substituting some animal protein for quality soy protein comes with no reduction in muscle-building effects. Most individuals can safely consume soy protein servings in place of animal protein for up to 50% of total intake, or approximately 1 gram per pound body weight.

Consuming higher amounts of soy protein powder is unlikely to cause issues for healthy persons. However, very high intakes above 2 grams per pound daily in conjunction with intense training may negatively impact testosterone levels over months or years. Moderation with any single protein source is wise.

Those with kidney disease should speak with their doctor about appropriate soy protein intake, as more protein from all sources may be detrimental to renal function if intake is not regulated appropriately.

The Bottom Line

Hopefully, this guide has helped explain all the key details about the various soy protein options available. When shopping, look for products clearly labeled with the protein percentage to understand what you are getting.

Isolated soy proteins provide an extremely pure, easy-to-digest vegan protein source that works excellently in shakes, smoothies, and high-protein prepared foods. Soy protein concentrates retain more nutritional value with moderate protein content. Textured soy proteins replicate meat extremely well while providing ample protein nutrition.

Research conclusively shows that consuming soy protein instead of some animal sources provides comparable muscle-building and workout recovery benefits for most goals. There are no health or safety issues associated with food-grade soy protein products. Incorporating more plant-based protein sources like soy into your diet can be an easy way to boost nutrition.

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