Protein Powder: An Ultimate Buyers Guide (2019)

Protein Powder

Protein powder is one of the most popular supplements used today. Even the supermarkets are catching on and are promoting protein shakes. With so many to choose from, it can be a minefield trying to pick the best one.

So which protein powders really are the best?

Well today you are going to learn exactly what protein powders are, the different types of protein powder, how you can use them for maximum benefit, which protein powders to avoid, along with a ton of other stuff such as how the quality of a protein is actually measured.

Regardless of your goal, whether you want to build lean muscle, or simply want a good vegan friendly protein shake to boost your protein intake, this article will take the guess work out of choosing the best protein powder that suits your needs.

Let’s get started.

What are protein Powders?

Protein powders are condensed protein based supplements that are derived from a number of various different animal and plant-based sources, and of course are very high in protein.

There are 3 basic forms of protein powder supplements:

1. Intact proteins (undigested)

Intact proteins are protein structures that haven’t been broken down or pre-digested by using chemical and enzymatic processing. Rather, the proteins remain ‘intact’, made of many chains of polypeptides. Intact proteins are proteins that have kept their original and complete protein structures.

Protein Concentrates

Protein concentrates are a type of intact protein. Simply put, concentrates are the proteins from a particular food source, such as milk, which are then extracted to achieve 60-80% protein content by weight.

The remaining 40-20% (by weight) of the powder comes from other macronutrients such as fats and carbohydrates.

Protein Isolates

Protein isolates are again a form of intact proteins. The difference between a protein concentrate and isolate is that the isolate has a higher percentage of protein. Further processing and filtration of proteins is what achieves a higher percentage protein in isolates relative to concentrates.

Typically an isolate will contain 90-95% protein by weight. As you can imagine, isolate protein powders are lower in fat, carbohydrate and anything else. If a protein isolate is derived from milk, it will also be significantly lower in lactose.

2. Hydrolysates (pre-digested)

Hydrolysates are manufactured using a process called protein hydrolysis, whereby intact proteins are run through an enzyme digester bath. Proteolytic enzymes are added to the protein, usually in a cold-processed mix, that typically target specific peptide cleavage bonds.

The end product yields a pre-digested protein mix of dipeptides and tripeptides (2 or 3 amino acids joined together).

Because hydrolysates are pre-digested, as you can imagine, they are absorbed far quicker and easier than intact proteins. This is also the basis to argue that hydrolysates are the same as intact proteins after they have been digested, and are therefore more bio-available.

3. Free-Form Amino Acids  (unbound)

Protein is made from long chains of amino acids in various different sequences and ratios. As I explained above, regarding protein hydrolysates, protein can be synthetically ‘digested’ into its amino acid counterparts.

Free form amino acids are processed one step further than protein hydrolysates, whereby the dipeptides and tripeptides found in hydrolysates are broken down into individual free-from amino acids.

Technically free form amino acids aren’t proteins, as they don’t have a protein structure. However, due to their nitrogen content, a basic laboratory protein assay test would show amino acids as protein.

This has recently caused controversy when it came to light that unscrupulous supplement companies used ‘amino spiking’ (adding amino acids to a low protein content protein powder) to claim on their labels, 80% or more protein content.

Needless to say, this technique would enable companies to save money but at the cost to the customer. Amino spiking allows less intact protein to be used, this shortfall in protein is then replaced with non-essential amino acids. Make no mistake; if you were to rely on a protein supplement that did not contain enough of, or all of the 9 essential amino acids, muscle protein synthesis could not occur.

Free form amino acids do have one distinct advantage over and above intact proteins and protein hydrolysates. Both of these have fixed amino acid ratios that are pre determined by the peptide sequences of the proteins.

Whereas, with free form amino acids, you can make any mix and ratio; you can determine the exact amino acid profile.


LEARN MORE > What Are Amino Acid Supplements? (AND WHY YOU NEED TO USE THEM)


When is the best time to use each type of protein powder?

Protein Shakes

There are 3 key times that you may want to consume some type of protein powder.

  1. As a meal replacement
  2. During your workout
  3. After your workout (Post workout)

Intact proteins and intact protein blends are the best type of protein powder for meal replacements. The reason for this is simple; they need to be digested and therefore will maintain blood levels of amino acids for several hours, feeding your body until your next meal.

If you are considering using a protein powder during your workout to help speed up recovery and boost your performance, you can use either a whey protein hydrolysate or free-form amino acids.

Both of these are absorbed faster than intact proteins, are completely pre-digested and won’t sit around in your stomach demanding blood flow for digestion. These types of protein powders will get straight to your working muscles right at the time when you most need them.

Hydrolysed whey protein (HWP) is perfect to use post workout. HWP is absorbed faster than intact proteins (1), and is efficient at stimulating muscle protein synthesis (MPU) (2) and is therefore great for boosting recovery.

Paying enough consideration to nutrient timing and when you plan to consume a particular protein is crucial in maximising its absorption.

Take whey isolate for example; research shows that whey isolate is rapidly digested, so much so, that whey-amino’s entering the bloodstream can be metabolised into glucose via a process called gluconeogenesis.

To reap maximum benefit from your protein powder, it is best to consume rapid digesting protein powders at times when your energy demands and protein requirements are elevated, i.e post workout.

7 most common protein sources that protein powders are derived from

Whey Protein Powder

Whey protein is a diary protein that derived from the manufacture of cheese. In fact, other than native whey (which is derived directly from from milk), all whey protein powders are manufactured as part of the production of cheese. Enzymes and other substances are added to milk to separate the whey part of the milk, which yields curds and whey.

The whey protein is then collected and processed using various types of cross flow micro filtration, ultra filtration, and membrane filtration systems that filter out the proteins from the remaining fat and carbohydrate. This produces a very high protein content whey protein powder.

However, due to cost, whey is most commonly sold as whey protein concentrate (WPC) which is cheaper than whey protein isolate (WPI). Whey protein isolate is a higher protein product and takes longer to filter.

Whey protein powder can also be bought as a combination of both concentrate and isolate, or hydrolysed whey is also another option but is also more expensive than whey protein concentrate.

The benefits of whey protein

  • High in the amino acid Cysteine which appears to increase levels of the antioxidant Glutathione (3).
  • High in BCAAs which have been shown to stimulate muscle protein synthesis (MPS) (4).
  • Whey protein is easily digested and readily absorbed
  • Whey contains various other protein fractions that positively affect immune system function.

Whey protein fractions

The term “whey protein” simply refers to a protein powder that is derived from the whey part of milk. However, whey protein actually contains various different protein structures and bio-active peptides, known as fractions, which collectively, form your whey protein powder.

Each protein fraction has a different structure, a different amino acid sequence, and therefore the properties of each protein fraction can vary.

Here is a list of the most common protein fractions that are contained in whey protein powder:

Lactoferrin (LF)

Lactoferrin is a 703 amino acid glycoprotein with a high affinity for iron, and binds to it with ease. lactoferrin helps in the transport and absorption of iron. This is because your small intestine has lactoferrin receptors and therefore facilitates the uptake of iron through the intestines (5).

Other health benefits are also associated with the consumption of lactoferrin proteins. Clinical studies show that it has antiviral, antibacterial, antifungal, anti-inflammatory and immunomodulatory functions (6).

Furthermore, lactoferrin is high in essential and branch chained amino acids, which is one of the main reasons why the use of whey protein in sports is now common place.

Glycomacropeptide (GMP)

Glycomacropeptide is a milk-derived bioactive peptide. GMP is of particular benefit to individuals who suffer from phenylketonuria (PKU) disease, as it does not contain the amino acid phenylalanine.

Aside from its nutritional value, GMP has a wealth of potential health-enhancing benefits due to its biological properties. Research shows that GMP displays a number of regulatory functions that signal various physiological activities such as endocrine and immune system function (7).

Immunoglobulins

Immunoglobulins are a class of proteins which function as antibodies (8) that bind to various different pathogens such as bacteria and viruses. Immunoglobulins therefore exhibit anti-bacterial and anti-viral properties. Whey protein includes a bunch of these immunoglobins in the form of; IgG1, IgG2, IgA and IgM.

α-lactalbumin (Alpha-lactalbumin or Alpha-lac)

Laboratory testing shows that α-Lactalbumin accounts for approximately 22% of total protein, and approximately 36% of the whey proteins in human milk (9).

α-lactalbumin has an amino acid profile that is beneficial to human nutrition. This is because it is high in essential amino acids (EAAs) including tryptophan & lysine, and contains relatively high amounts of the conditionally essential amino acid cysteine, along with the branched chain amino acids (BCAAs) leucine, isoleucine, and valine.

β-lactoglobulin (Beta-lactoglobulin or Beta-lac)

β-Lactoglobulin is the most abundant whey protein fraction in cow’s milk, where it constitutes around 50% of the total protein content. Research shows that β-Lactoglobulin exhibits an immunomodulatory effect by promoting cell proliferation via a receptor-mediated pathway and therefore can strengthen immune system function (10).

Lactoperoxidase

Lactoperoxidase is believed to be an antimicrobial protein which is why it is often added to milk to increase its shelf life.

Summary of whey protein fractions

Whey protein is a collection of different dairy proteins and bioactive peptides. Collectively these whey protein fractions are of great benefit to human nutrition; they are high is essential amino acids and exhibit other beneficial immunomodulatory functions that can help improve your immunity and contribute toward good health.

Whey protein that you should avoid

All whey protein is high in protein essential amino acids and branched chain amino acids. However, not all whey proteins are equal. Both the quality of the milk that whey protein is derived from, and how it is processed ultimately affects the quality of the end product.

The best whey is derived from cows that are hormone and anti-biotic free and are 100% grass-fed. Milk from these types of cows is inarguably the best.

Be aware of the subtle difference between a protein powder claiming to be from “grass-fed” cows rather than 100% grass-fed cows.

This can be misrepresentative because it is possible that “grass-fed” cows may only feed on grass a portion of the time. If in doubt, I’d suggest contacting the company directly and asking them to clarify the position or look for 100% grass-fed produce.

Cold Filtered Whey Protein vs. Ion Exchange.

An important variable to look for when buying a whey protein powder is to make sure that it has been cold-filtered and/or cold processed, rather than ion exchanged.

Filtration systems use the finest gauge filters to separate the molecules of protein from the fats, carbohydrates and lactose. Whereas ‘ion-exchange’ uses acids and other chemicals that make changes in PH to separate the macronutrients.

Although ion-exchange whey is exceptionally high in protein, it lacks some of the valuable protein fractions that are found in filtered versions, and because ion-exchange processing doesn’t filter, bacteria can also be left in the final product.

Acid and heat processing such as pasteurising can also denature proteins. If a protein becomes denatured its structure changes which means that it isn’t as bio-available and therefore your body cannot use it as effectively as it can with an undenatured whey protein.

The bottom line

Look for a cold-processed whey protein powder that is derived from milk produced in Ireland, or specific regions of Europe such as Germany, Belgium, France, and the Netherlands. These countries all have first class dairy industries and their reputations for producing the world’s finest grass-fed meat and dairy products are second to none.

Casein Protein Powder

Casein protein powder is also derived from milk, yet it is much slower digesting than whey protein (11). Once ingested the PH of your stomach causes the casein protein to form a gel like substance which essentially slows down the transit time from the stomach by increasing the time it takes for your stomach to empty.

Due to its longer digestion time casein yields a more steady influx of amino acids into your bloodstream, making it ideal to consume as a meal replacement or before you go to bed.

Casein is high in branched chain amino acids which is why studies show that it can stimulate muscle protein synthesis, albeit not as effectively as whey protein does. It is also referred to as being a complete protein because it contains all 9 of the essential amino acids.

Egg Protein Powder

Of all the protein containing foods, whole egg is one of the most complete (in terms of its amino acid profile) and bio-available proteins. In fact, whole egg is one of the highest scoring foods across all protein quality evaluation methods (PDCAAS, BV, NPU, PER).

Unfortunately protein powders derived from eggs are not typically the same quality as their whole food counterpart. This is because egg protein powders are ordinarily made from the egg whites , while the egg yolks are excluded due to their fat content.

The yolk of an egg also contains high quality proteins and therefore if removed, lowers the value of the protein.

Even though egg whites aren’t as complete as a whole egg, egg whites do contain all 9 essential amino acids and are a great source of nutrition.

Another consideration when buying an egg protein powder, just as with whey, is to determine what type of animal the eggs came from. Where the hens caged or were they free to roam? What did they feed on? Did they eat GMO grains or follow their natural diet of insects, worms, and other natural foods? Were the hen’s antibiotic and hormone free?

All of these factors affect the quality of the eggs produced. Fundamentally nutrients are passed down the food chain and not only do you literally become what you eat, to a certain degree, you are also what your food ‘ate’.

Pea Protein Powder

Pea protein is a plant-based protein and is therefore suitable for a wider variety of people to consume relative to that of dairy and animal derived proteins. Pea protein powder is popular with vegetarians and vegans, and is also great for people who are allergic to dairy produce and/or lactose intolerant.

The most common form of pea protein powder is derived from the yellow split pea variety. There are claims that pea protein powder does not contain all of the 9 essential amino acids, however this claim is completely unfounded and untrue.

Laboratory analysis of the protein content of plant-based proteins, have indeed determined that pea protein is complete in all 9 of the essential amino acids (12). The brilliant work of McCance and Widdowson who have become a world authority on food composition, also confirms the same.

However pea protein powder is not as high in BCAAs and EAAs as for example whey protein, which is why it consistently scores less in every method of protein quality evaluation.

Hemp Protein Powder

Protein powder made from hemp has recently taken the protein market by storm. Hemp appears to be synonymous with marijuana, and although the two plants are of the same genius, hemp naturally contains only a miniscule amount of the psychoactive compound THC (tetrahydrocannabinol).

You could say that hemp is marijuana without the THC. Furthermore, hemp is perfectly legal.

Hemp protein powder is made by pulverising hemp seeds into a fine powder. In terms of its protein content, hemp protein powder is typically lower in quantity and lower in quality than other protein powders such as whey or pea.

However hemp protein powder isn’t filtered or made into a concentrated or isolated protein, and therefore contains other macronutrients.

Therefore hemp invariably offers some unique benefits such as being high in fiber and high in quality omega 3 & 6 fatty acids.

While hemp scores lower on protein evaluation tests, it is a complete protein and does contain all 9 essential amino acids, albeit in lower quantities than other protein powders.

You can definitely supplement with it to boost your protein intake.

If you are thinking of switching to a plant-based hemp protein powder look for one that is organic/NON-GMO. Do not be fooled into thinking just because something is plant-based, it is somehow healthier.

Unfortunately, the use of genetic modification, synthetic fertiliser and pesticides, have worked their way into every crack and crevice of the commercial food supply.

Brown Rice Protein Powder

Of all the protein sources that are used to manufacture protein powders, brown rice protein is the lowest quality in terms of human nutrition. Some may argue that rice feeds around half the population of the world.

This may be the case, yet rice protein in general doesn’t contain amino acids in the right ratios to support any substantial amount of lean athletic muscle mass.

In fact, almost all predominant rice-eaters are small and sparsely muscled people.

In terms of protein evaluation scoring, brown rice protein is always on the lower end of the scale, it is too low in lysine and tryptophan for efficient muscle building.

Protein Blends

A blended protein powder contains proteins from various different sources. These tend to be either a mix of dairy protein sources or plant-based protein sources. In either case, a protein powder blend has a couple of distinct advantages over single source protein powders.

  1. Blends have a more complete overall amino acid profile. Amino acids that one protein source may lack, can be compensated by another protein source that may be higher in that particular amino acid.
  2. Protein blends usually contain a mixture of proteins that vary in the rate of digestion. By combining slow and fast digesting proteins can yield a quick influx of amino acids that is then sustained by slower digesting proteins.

Typically protein blends are better suited for meal replacements rather than post workout.


LEARN MORE > Creatine Loading: A Definitive Guide (LATEST RESEARCH 2019)


How is protein quality measured?

Protein Powder Used By Male Athletes

Over the years scientists have developed a number of protein quality evaluation methods that assess protein digestion, bioavailability and absorption.

Protein Digestibility Corrected Amino Acid Score (PDCAAS)

Using PDCAAS, proteins are tested then assigned a score, the highest value being (1.0) which means that a particular food provides high quality protein that contains all 9 of the essential amino acids.

This scoring system is based on the amino acid requirements of “humans” and their ability to digest a particular protein.

PDCAAS compares the concentration of the first limiting essential amino acid in the test protein (the test protein is the protein that is being evaluated) with the concentration of that amino acid in a reference (scoring) pattern.

The formula used to calculate PDCAAS is as below:

(mg of limiting amino acid in 1 g of test protein / mg of same amino acid in 1 g of reference protein) x fecal true digestibility percentage.

Although the Food and Agriculture Organization (FAO) and World Health Organization (WHO) along with the US FDA have allotted PDCAAS as their preferred best method of measuring protein quality, PDCAA scoring does have its limitations and does not take in to account some important factors.

For example, the reference pattern is based on the minimum amino acid requirements for tissue growth and maintenance and does not necessarily reflect the optimum intake.

Furthermore these values relate to preschool-age child amino acid requirements. Needless to say, protein requirements of adults and athletes and people as individuals can vary tremendously.

Biological Value (BV)

In contrast to PDCAAS, Biological Value doesn’t directly examine the amino acid content of a protein food. Rather, BV evaluates the percentage of protein that has been absorbed from a particular food, which then becomes incorporated into your structure (% of absorbed nitrogen retained in the body). BV is based on the assumption that protein foods are the only source of nitrogen.

The formula used to calculate Biological value (percentage evaluation) is as below:

BV = ( Nr / Na ) * 100

Where:

Nr = nitrogen incorporated into the body on the test diet
Na = nitrogen absorbed in proteins on the test diet

Needless to say, the maximum score achievable by any protein food is 100%. You cannot possibly absorb more protein than you consumed.

That said, due to the limitations of BV protein testing, (direct measurement of Nr is almost impossible), sometimes BV is evaluated relative to that of a readily utilisable index protein (usually whole hens egg), which is given the score of 100.

The formula used to calculate Biological value (relative evaluation) is as below:

To calculate the relative biological value, two tests are performed on the same person; one with the test protein source and one with a reference protein.

Relative BV = ( BV(test) / BV(egg) ) * 100

Where:

BV(test) = percentage BV of the test diet for that individual
BV(whole egg) = percentage BV of the reference (whole egg) diet for that individual

In relative BV evaluation, protein values can exceed 100. For example, the percentage BV of whole egg scores 93.7%. This opens the door for any protein food with a percentage BV of 93.7% or more, to score a relative BV value of over 100. This is apparent with whey protein which scores a relative BV of 104, while its percentage BV is under 100%.

Protein Efficiency Ratio (PER)

PER works on a similar basis to BV whereby the weight gain of a test subject is divided by their intake of a particular protein containing food during a set amount of time (the test period ), in order to determine how much protein the test subject absorbed.

The formula used to calculate Protein Efficiency Ratio is as below:

PER = Gain in body mass (g) / Protein intake (g)

The logic behind PER is that it evaluates how much of a protein has been absorbed.

Net Protein Utilisation Index (NPU)

NPU is the ratio of amino acids supplied from a particular protein food that are incorporated into proteins in the human body, relative to the ratio of amino acids supplied from the protein food; hence the total amount of protein absorbed from a particular food.

After NPU testing a protein food is assigned a score ranging from 0 to 1 (or 100), with a value of 1 (or 100) respectively.

However this figure can almost never be 100% accurate because it does not allow for things such as the concept of labile protein reserves and your body’s ability to ‘salvage’ amino acids which were not provided from the tested protein food, yet could contribute toward protein synthesis.

Theoretically NPU values can be calculated by measuring dietary protein intake minus the recorded value of total nitrogen excretion.

Most governing health bodies now use PDCAAS over NPU.

Protein quality rankings:

Protein TypePERBV (relative)NPUPDCAAS
Beef 2.9 80 73 0.92
Black Beans 0 0 0.75
Casein 2.5 77 76 1.00
Egg 3.9 100 94 1.00
Milk 2.5 91 82 1.00
Peanuts 1.8 0.52
Soy protein 2.2 74 61 1.00
Wheat gluten 0.8 64 67 0.25
Whey protein 3.2 104 92 1.00

Table Data Source: PubMed

What are your protein requirements – do you need to use a protein powder supplement?

Protein Powder Used By Female Athletes

According to Public Health England, the Government dietary recommendations for protein intake has been assigned a dietary reference value of 55.5 grams and 45.0 grams per day, for men and women aged between 19 – 64 years old, respectively.

However this guideline is nowhere near accurate for athletes. There are no end of studies that prove athletes who regularly partake in resistance training and other forms of strenuous exercise, require more protein.

For example a recent study (13) led by Dr Oliver Witard from the University of Sterling, has set out new international guidelines for protein intake in track and field athletes.

Dr Witard, of the Physiology, Exercise and Nutrition Research Group at Stirling University, stated:

“Track and field athletes engage in vigorous training that place stress on physiological systems requiring nutritional support for optimal recovery. In this paper, we highlight the benefits of dietary protein intake for training adaptation, manipulating body composition and optimising performance in track and field athletes.”

In his final conclusion, Dr Witard recommended that athletes whose goal is to increase muscle mass ought to consume around 1.6 grams of protein per kilogram of body mass, every day.

If you are an athlete, and I don’t necessarily mean a competitive one, and regularly engage in resistance training and/or vigorous exercise, it’s a sure bet that you will require more protein than the governmental dietary reference values.

Eating up to 1.6 grams of protein per kilogram of body weight from whole food can certainly be tough. Aside from that, gobbling down several chicken breasts followed by cans of dry tuna every day can also be tedious. A high quality whey protein powder can definitely come in handy, while boosting recovery and promoting muscle protein synthesis.

Can you consume too much protein powder?

It is absolutely possible to consume too much protein powder, and furthermore, too much protein in general – irrespective of the source. A sedentary person does not have the same protein requirements as that of an athlete.

Regardless of your own personal protein requirements, if you consistently consume excessively high amounts of protein (which can significantly vary from individual to individual), there could be some serious health implications.

When the protein foods you eat are digested, your blood levels of amino acids increase. Excess amino acids (caused from consuming too much protein) are metabolised into carbon dioxide and water, along with ammonia (14) which is toxic to all tissues. The good news is your body has an in-built safety mechanism whereby it converts the ammonia in to the less toxic urea.

Urea is then excreted from your body by your kidneys. However, if you consistently consume protein beyond your kidneys capacity to handle these toxins, you will eventually overload them, causing them to become inflamed and poison your blood.  

If you are concerned that you may be consuming too much protein, look out for lower back pain and a general feeling of discomfort. These are both tell-tale signs of chronic elevated urea. You can also have your blood tested by your doctor; they will look at a blood urea nitrogen biomarker (BUN) to determine if you have any problems.

Conclusion

Protein powders can be used to supplement a whole food diet and have various health benefits. Although there are many different types of protein powder, whey proteins have the highest biological value in human nutrition. Whey proteins are also quite unique as they also offer other added immune boosting benefits.

Consuming the right protein at the right time is crucial in gaining maximum benefit from your protein powder. Whey proteins are quick digesting and are therefore best consumed post workout, while casein and protein blends are preferable for meal replacements or pre bed.

Plant-based protein powders don’t provide the amino acids in the same ratios and quantities as diary proteins do, but these can still be effectively used to boost your protein intake.

The choice is yours.

So now it’s you turn, what is your favourite protein powder, and when do you use it?

Scientific Reference Data:

  1. Protein hydrolysates in sports and exercise: a brief review.
    https://www.ncbi.nlm.nih.gov/pubmed/24482579/
  2. Whey Protein Hydrolysate Increases Amino Acid Uptake, mTORC1 Signaling, and Protein Synthesis in Skeletal Muscle of Healthy Young Men in a Randomized Crossover Trial.
    https://www.ncbi.nlm.nih.gov/pubmed/31095313
  3. Effect of whey protein isolate on intracellular glutathione and oxidant-induced cell death in human prostate epithelial cells.
    https://www.ncbi.nlm.nih.gov/pubmed/12537959
  4. Whey Protein Ingestion Activates mTOR-dependent Signalling after Resistance Exercise in Young Men: A Double-Blinded Randomized Controlled Trial
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257597/
  5. Lactoferrin: A Natural Glycoprotein Involved in Iron and Inflammatory Homeostasis
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5618634/
  6. Immunomodulatory effects of lactoferrin
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4814036/
  7. Glycomacropeptide Bioactivity and Health: A Review Highlighting Action Mechanisms and Signaling Pathways
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6471465/
  8. Perspectives on Immunoglobulins in Colostrum and Milk
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257684/
  9. Applications for α-lactalbumin in human nutrition
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5934683/
  10. β-Lactoglobulin Influences Human Immunity and Promotes Cell Proliferation
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5124466/
  11. Casein Protein Supplementation in Trained Men and Women: Morning versus Evening
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5421981/
  12. Protein content and amino acid composition of commercially available plant-based protein isolates.
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6245118/
  13. Dietary Protein for Training Adaptation and Body Composition Manipulation in Track and Field Athletes
    https://journals.humankinetics.com/view/journals/ijsnem/29/2/article-p165.xml
  14. Protein turnover, ureagenesis and gluconeogenesis.
    https://www.ncbi.nlm.nih.gov/pubmed/22139560

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