The soy protein guide

This guide examines the benefits and dosages of soy protein and will show you the different types of soy protein available and how they can help you achieve your goals.

This guide will cover the following topics:

• What is soy protein and where does it come from?
• The four types of soy protein
• Soy protein concentrate
• Soy protein Isola
• Soy flour
• Soy protein hydrolyzate
• Why is it beneficial to consume soy protein?
• Is soy protein a viable option compared to other protein sources?
• How and when should you use a soy protein supplement?
• Which soy protein supplement is right for which needs?

Soy protein is a fairly esoteric supplement for many competitive bodybuilding and figure class athletes, weight trainers, athletes and even general health & fitness enthusiasts. Soy protein often gets the short end of the stick compared to other protein sources as it has lower bioavailability and lower essential amino acid content than whey protein, casein and egg proteins. Nevertheless, soy protein is a useful alternative protein source that has a place in everyone's diet to some extent, especially for vegans.

Scientific research continues to provide further evidence that protein requirements are generally higher in active people, particularly those who train with weights. For understandable reasons, many people see the use of protein supplements as a convenient and useful way to meet their protein needs.

The following guide will show you exactly what soy protein is, where it comes from, how it is produced, how you can benefit from its use and what side effects it may have. You will also find answers to some frequently asked questions about this protein source.

What is soy protein and where does it come from?

The term "soy" generally refers to the soybean, a common legume originally from East Asia. Soy protein powder is made from defatted soy flakes/defatted soybean meal and is available in four forms:

• Soy protein concentrate
• Soy protein isolate
• Soy flour
• Soy protein hydrolyzate

Soybeans contain a whole range of different protein fractions, of which globulins make up the largest proportion (1). For the sake of simplicity, we will simply use the term soy protein as a collective term for all the protein fractions contained in soy in the rest of this article.

Unlike other plant proteins, soy protein is a complete protein source, meaning that it contains all 9 essential amino acids (more on why this is important later). Soy protein is extremely heat stable and is highly soluble in warm water. Due to its relatively neutral taste, it can be used as a substitute or addition to a variety of different food products.

The production of soy protein

The production of soy protein from soybeans can be achieved using different extraction and filtration methods, depending on the desired protein content. Like other protein powder supplements, the extracted product is spray-dried together with soy lecithin to achieve the desired product in powder form, which can then be further modified by supplement manufacturers by adding flavors, colors and more.

Different types of soy protein

Soy protein concentrate

Soy protein concentrates contain around 70 to 80% protein, while the rest consists of carbohydrates and fats. This product is made from coarse soy grits by extraction through heat treatment or mixing with organic solvents (2)

Soy protein isolate

Soy protein isolate is produced from defatted soy flakes by means of alkaline extraction. The finished product often has a protein content of over 90%, whereby most of the carbohydrates and fats contained in soy have been removed.

Soy flour

Soy flour consists of defatted, coarsely ground soy flakes. Of the four types of soy protein described here, soy flour contains the lowest proportion of protein. The typical protein content of soy flour is in the range of 40 to 60% (3).

Soy protein hydrolyzate

Soy protein hydrolyzate is produced from soy protein concentrate or soy protein isolate by means of enzymatic hydrolysis. Basically, this treatment "pre-digests" the protein by breaking down peptide bonds in the protein. This makes soy protein hydrolysate faster and easier to absorb in the small intestine due to the shorter amino acid chain length (4).

How does soy protein work and what are its benefits?

Proteins are essentially macromolecules that play a crucial role in muscle development and maintenance (and many other physiological processes). Proteins are made up of amino acid peptides that are linked together. So basically, amino acids are the building blocks of proteins.

Proteins act as building blocks for muscle tissue and muscle tissue is the richest reservoir of amino acids in the human body (5). From a physiological perspective, amino acids play a role in a myriad of processes, including neurotransmission, energy production, brain metabolism, cardiovascular function, immune system function and many others (6).

The consumption of soy protein has a variety of benefits associated with the biological role of the amino acids and phytochemicals contained in soy protein.

As mentioned above, soy protein is a complete protein (i.e. it contains all 9 essential amino acids) with a nominal content of L-leucine, which is critical for stimulating the mTor pathway, which regulates protein synthesis, among other things. Thus, soy protein plays a role for individuals who want to improve their muscle development, fitness or just the general function of their body (7).

In addition, it has been suggested that a nominal dose of soy protein (approximately 25 grams) per day may play a role in reducing the risk of heart attack, lowering cholesterol levels, lowering blood pressure and protecting against osteoporosis (8, 9, 10). This is probably related to the isoflavones contained in soy protein.

An overview of the benefits of soy protein:

• It is a complete protein source that is also suitable for vegans
• It is easily absorbed and digested
• It can be conveniently added to the diet and is suitable for baking/cooking
• It increases the anabolic response to training with weights
• It improves the function of the immune system, especially in physically active people (11)
• Helps maintain muscle mass and prevent age-related muscle atrophy
• It may reduce the risk of heart disease and high cholesterol levels (8, 9)
• It could prevent degeneration of bone tissue/osteoporosis (10)

A comparison of the quality of soy protein with the quality of other protein sources

The two most important and popular indicators for determining the overall quality and efficiency of a protein source are the biological value and the Protein Digestibility Corrected Amino Acid Score (PDCAAS).

The biological value of a protein source refers to a practical measurement that determines the degree to which an organism is able to utilize a protein. This value is calculated by analyzing the nitrogen retention in the living organism after consumption of the protein source being tested (12).

The PDCAAS is a number between 0 and 1, which evaluates the protein quality based on the amino acid content in relation to the human requirement for these amino acids. Basically, the higher the biological value and PDCAAS of a protein source, the more efficiently it can be used by a living organism.

Who can benefit from using soy protein supplements?

Those who can most obviously benefit from supplementing with soy protein are those who are physically active and looking for an alternative to animal protein sources. Soy protein is also definitely a useful addition to whey protein and casein supplements. Here is a short list of people who may consider supplementing with soy protein (always assuming they are not allergic to soy products):

• Bodybuilders & strength athletes
• Competitive athletes
• Vegetarians/vegans
• People who suffer from a milk allergy or lactose intolerance
• Recreational athletes
• Anyone looking for an easy way to increase the protein content of their diet

Are there other foods that contain soy protein?

Yes, a whole range of foods contain soy protein. These include soy flour, soy sauce, soybeans, soy nuts, soy milk, tofu, edemame, tempeh, miso and more.

If you are not sure whether a food contains soy, a quick look at the list of ingredients will tell you.

Does soy protein have any side effects?

Soy protein is generally a safe and well-tolerated food as long as you do not suffer from a soy allergy. However, under certain circumstances there may be some risk of the following side effects:

• A bloated feeling, stomach cramps and stomach upset
• Nausea
• Increased intestinal activity/flatulence
• Allergic reactions
• Increased estrogen receptor activity and lower testosterone levels (14)

Note: The significance of the hormonal impact of regular soy consumption is a topic that requires further investigation.

These side effects can generally be easily alleviated by controlling overall soy consumption. If a nominal dose of soy protein consistently results in digestive discomfort, then the use of another protein supplement or possibly another protein source should be considered.

How and when should I use a soy protein supplement?

Soy protein supplements are usually a little more bitter and grainy than whey protein supplements. However, with a little creativity, it is still possible to prepare some delicious protein-rich shakes and foods with soy protein powder.

Soy protein supplements, like other protein sources, do not have to be restricted to certain times of the day. Soy protein is a protein source like any other: it can and should be used whenever you are looking for a protein source to add to your diet.

How much soy protein should I use?

There is no definitive answer to this question, as protein requirements vary from person to person. The first thing you should do is determine your protein and nutrient requirements, which you can do with the help of numerous calorie calculators available on the internet.

In addition, your soy protein consumption will likely vary based on what type of diet you follow. A vegan may need more soy protein to meet their daily protein requirements.

For other people - and especially men - the officially recommended daily amount of about 25 grams of soy protein per day should be a safe and healthy dose that should not have significant effects on endocrine function.

Choosing the right soy supplement

It should be noted that soy protein, like any other protein source, is technically a food source. Choosing the right soy protein supplement depends on a number of factors, including your budget, protein quality, taste, desired nutrient content and intended use. Below you will find a list of the different types of soy protein supplements with additional information that will help you decide which of these protein types best suits your needs:

Pros and Cons of Soy Protein Concentrate:

Soy protein concentrate is usually the most cost-effective soy protein supplement that can be used in a variety of situations. Depending on the protein concentration of the powder (generally 70 to 80%), soy protein concentrate can be an excellent option for those on a budget who don't mind a little more fat and carbohydrates in their soy protein supplement. Soy protein concentrate is also great for cooking and baking.

Advantages and disadvantages of soy protein isolate:

Soy protein isolate has high bioavailability, is easily digestible, low in fat and carbohydrates and contains a high protein content (generally over 90%). The main disadvantages of soy protein isolate are that it is more expensive and slightly "grittier" in texture than soy protein concentrate. Just like soy protein concentrate, soy protein isolate is also an excellent ingredient for various recipes.

Advantages and disadvantages of soy protein hydrolyzate:

Even though soy protein hydrolysate is the purest form of soy protein, it is more expensive and less available than soy protein concentrate and isolate. The main advantage of soy protein hydrolysate is that it is very well tolerated and easy to digest. In fact, many infant formulas contain soy protein hydrolysate because it is so easily absorbed. If you're willing to pay the higher price, soy protein hydrolysate is certainly worth the money, especially if you don't tolerate soy protein concentrate and isolate as well.

Soy protein - frequently asked questions:

Q: Does soy protein really increase estrogen levels in men while lowering testosterone levels?

A: As mentioned above, the significance of soy protein consumption on hormonal status in men has not been fully researched. Most studies have examined consumption of 50 to 60 grams of pure soy protein per day, which is twice the officially recommended amount. Therefore, if you are worried about effects on your endocrine system, it is recommended that you stick to a conservative amount of 20 to 30 grams of soy protein per day.

Q: I suffer from lactose intolerance. Can I still use soy protein supplements?

A: Soy protein powder does not contain milk sugar (lactose) and is therefore a suitable source of protein for people who suffer from lactose intolerance.

Q: I am allergic to milk. Is a soy protein supplement safe and harmless for me?

A: Soy protein does not contain milk ingredients and should therefore be a safe alternative to milk protein sources.

Q: Is it true that a high protein diet is bad for the kidneys?

A: This misconception is related to the problems that people with impaired kidney function suffer from when they chronically consume high amounts of protein. Assuming you don't go way over your protein requirements on a daily basis and have healthy kidneys, you don't need to worry about your kidneys.

Q: Can I combine a soy protein supplement with other supplements in powder form such as creatine, glutamine, etc.?

A: Yes, that is perfectly fine.

Q: Does it matter what liquid I mix my soy protein powder with?

A: No, but I would try to use matching flavors unless you are trying to create some "Frankenstein" shakes like cinnamon flavored protein mixed in grapefruit juice.

Q: Will cooking/baking denature protein?

A: Yes, but this has no significant effect on how your body uses the protein because a denatured protein is basically a hydrolyzed protein: You're still consuming all the amino acids that were in the protein to begin with.

References:

1. Derbyshire,E. et al.1976. review: Legumin and vicilin, storage proteins of legume seeds" Phytochemistry 15:3.
2. Lawhon JT, Mulsow D, Cater CM & Mattil KF. 1977. production of protein
3. Isolates and concentrates from oilseed flour extracts using industrial ultrafiltration and reverse osmosis systems. Journal of Food Science 42(2):389-394.
4. Lennon AM, Ramsey HA, Alsmeyer WL, Clawson AJ & Barrick ER. 1971. soy flour as a protein source for early-weaned pigs. J Anim Sci 33(2):514-519.
5. Zorin SN & Baiarzhargal M. 2009. preparation of food proteins enzymatic hydrolysates of dietary proteins using some commercial enzyme preparations and various schemes of hydrolysis. Biomed Khim 55(1):73-80
6. Timmerman KL, Volpi E. Amino acid metabolism and regulatory effects in aging. Curr Opin Clin Nutr Metab Care. 2008 Jan;11(1):45-9.
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8. Drummond MJ, Dreyer HC, Pennings B, Fry CS, Dhanani S, Dillon EL, Sheffield-Moore M, Volpi E, Rasmussen BB. Skeletal muscle protein anabolic response to resistance exercise and essential amino acids is delayed with aging. J Appl Physiol. 2008 May;104(5):1452-61.
9. Zhou JR, Yu L, Zhong Y & Blackburn GL. 2003. soy phytochemicals and tea bioactive components synergistically inhibit androgen-sensitive human prostate tumors in mice. J Nutr 133(2):516-521.
10. Anderson JW, Johnstone BM & Cook-Newell M. 1995. Meta-analysis of the effects of soy protein intake on serum lipids. New Engl. J. Med 333:276-282.
11. Anthony MS, Clarkson TB, Hughes CL, Jr, Morgan TM & Burke GL. 1996.
12. Soybean isoflavones improve cardiovascular risk factors without affecting the reproductive system of peripubertal rhesus monkeys. J Nutr 126(1):43-50.
13. Cassidy A. 2003. Potential risks and benefits of phytoestrogen-rich diets. Int J Vitam.
14. Martin CJ, Robison R. The Minimum Nitrogen Expenditure of Man and the Biological value of various Proteins for Human Nutrition. Biochem J. 1922;16(3):407-47. PubMed PMID: 16743096; PubMed Central PMCID: PMC1259089.
15. Nutr Res 73(2):120-126.BV of Protein Sources. N.d. NA, Online. Cut and Jacked. Web. 1 Apr. 2013.
16. Hamilton-Reeves, J. M., Rebello, S. A., Thomas, W., Slaton, J. W., & Kurzer, M. S. (2007). Isoflavone-rich soy protein isolate suppresses androgen receptor expression without altering estrogen receptor-β expression or serum hormonal profiles in men at high risk of prostate cancer. The Journal of nutrition, 137(7), 1769-1775.

Source: https://www.muscleandstrength.com/expert-guides/soy-protein