Whey protein powder

Whey protein powder:

A complete A-Z guide to all types of whey protein supplements

Whey protein is considered a basic supplement used by athletes, bodybuilders and fitness enthusiasts to support muscle recovery, lean muscle mass gain and overall health.

This guide will teach you the following:

• What whey protein is and where it comes from.
• Who can benefit from using whey protein supplements.
• How to choose the right whey protein supplement.
• How much whey protein you should use and what the best times are.

What is whey protein?

Whey protein is a term used to describe a group of milk proteins that are isolated from whey, which is a by-product of the coagulation of milk during the cheese-making process. Most people think that whey protein is simply a mixture of the typical amino acids we know, but in reality whey protein contains many more molecules.

The mixture of proteins usually contains about 65% beta-lactoglobulin, 25% alpha-lactalbumin, 8% bovine serum albumin and small amounts of immunoglobulins, lactose and fat.

How is whey protein produced?

Whey protein can be made directly from milk or even cheese, but almost all known brands of whey protein are made directly from milk.

First, the whey protein is separated from the milk using a sieving process. The result is a liquid whey product. Then the first step is pasteurization using an ultra-high, short heating process.

Basically, the product is heated to the required minimum temperature of 161 °F for 15 seconds. Milk is pasteurized to kill any harmful bacteria that may be present in the milk.

The next step is to isolate the protein from the liquid whey. This can be achieved by ion exchange or mechanical filtration.

The ion exchange process often requires the use of acids (e.g. hydrochloric acid) or bases (e.g. sodium hydroxide), which can lead to denaturation of the protein.

While the chemical-based process of ion exchange is cheaper and often allows more amino acids to be isolated, the disadvantage of this process is that some of the other important compounds contained in whey protein, such as lactoferrin and many of the immunoglobulins, are lost.

The mechanical filtration process, often known as cross-flow filtration, is a physical process that often results in a better product. However, this process can be more expensive and laborious.

The type and sizes of filters used and the number of successive filtration steps are key to what type of whey protein is produced. The finer the filter and the more frequently the product is filtered, the purer the end product will be. With each filtration step, the amount of lactose, fat, ash and other small impurities in the final product decreases.

The type of filter and the number of filtration steps are the primary difference in the production of different types of whey protein (primarily isolates and concentrates)

Types of whey protein

There are three main types of commercially available whey proteins: Whey protein isolate, whey protein concentrate and whey protein hydrolysate. Let's look at these in detail:

Whey protein isolate

Whey protein isolate is considered to be the purest form of whey protein available. It contains between 90 and 95% whey protein, very little fat (0.5 to 1%) and very little lactose (0.5 to 1%). This makes whey protein isolate a good source of protein for people who suffer from lactose intolerance or other lactose digestion issues.

One thing that should be mentioned is that whey protein isolate often lacks a lot of the other beneficial compounds of whey protein including immunoglobulins and other small molecules that have beneficial properties for health. So if you choose whey protein isolate, you may be missing out on some of the magic.

Whey protein concentrate

Whey protein concentrate has a lower protein content, typically ranging from 25 to 98%, with most commercially available concentrates containing between 70 and 80% protein. Whey protein concentrate often contains between 4 and 8% lactose, fat and other minerals.

This type of whey protein is also commonly found in protein bars and other food products.

Whey protein hydrolysates

Whey protein hydrolysates - also known as hydrolyzed whey protein - consist of whey protein that has been enzymatically treated to break down long protein chains into shorter ones. This process makes the whey protein easier to absorb by the body and often reduces the potential for allergic reactions and digestive problems. As such, it is often used in infant products, sports products and medical nutrition products.

A direct comparison of the primary types of whey protein

Type of whey protein	Protein concentration	Other compounds	Allergens
Whey protein isolate	90 - 95% whey protein	Only traces of fat, lactose or other minerals	Low in case of lactose intolerance, high in case of milk protein allergy
Whey protein concentrate	25-89% whey protein. Typical concentrations found in commercial products are 80%	Contains some fat, lactose and other minerals. Typically, the amount of these ingredients decreases as the protein concentration increases.	High for lactose intolerance, high for milk protein allergy
Whey protein hydrolyzate	80 - 90% whey protein, whereby the concentration varies greatly from product to product	Highly variable from product to product	High for lactose intolerance, low for milk protein allergy

The benefits of whey protein

Whey protein supplementation is very popular among athletes as it has been reported to increase athletic performance. Whey protein is a popular protein supplement designed to provide increased muscle strength and improved body composition due to its high content of essential amino acids and branched-chain amino acids, resulting in a higher biological value (1-4).

In addition, whey protein supplementation has been shown to reduce oxidative stress by increasing endogenous glutathione production and improve compromised digestive health associated with intense exercise (5-8).

While most of the topics discussed in this article are specific to whey protein supplementation, I would like to remind everyone that whole food sources of whey protein may be superior to whey protein supplementation in terms of nutritional synergy.

Increased strength and lean body mass

Most sporting events rely on muscle force production, and a greater ability to produce force is associated with increased performance. Since force equals mass times acceleration (F = M * A), increasing muscle mass is the most common way athletes aim to increase their force production.

Skeletal muscle hypertrophy requires proper resistance training and nutritional status in which muscle protein synthesis exceeds muscle protein breakdown.

One of the main concepts in the literature dealing with skeletal muscle hypertrophy is the idea of net protein balance. Net protein balance is defined as muscle protein synthesis minus muscle protein breakdown. Thus, skeletal muscle hypertrophy will occur if muscle protein synthesis is higher than muscle protein breakdown (9).

One of the critical factors influencing muscle protein synthesis and muscle protein breakdown is the availability of amino acids (10, 11). Whey protein supplementation is a source of amino acids with high biological value and is said to increase muscle mass and strength.

There is a large body of scientific research that has investigated the effectiveness of whey protein supplementation in increasing strength and muscle mass. The results of these studies are not completely consistent, but a large body of evidence suggests that whey protein supplementation increases both strength and muscle mass (12-15).

In addition, scientists have recently shown that whey protein ingredients upregulate cell signaling pathways - specifically mTOR - that are responsible for muscle protein synthesis and muscle hypertrophy (16).

Whey protein and glutathione

Oxidative stress represents an imbalance between the antioxidant defense system and the production of reactive oxygen species (17). Oxygen consumption during heavy exercise can increase up to 100 times normal levels at rest, increasing free radical production, resulting in oxidative stress.

Although the data is inconclusive, existing studies show increased free radical production and increased cellular damage after heavy resistance training (18).

Athletes are at higher risk of oxidative stress than their physically inactive counterparts due to the increased pro-oxidant processes they expose themselves to (19). The increased levels of oxidative oxygen species produced during heavy exercise must be reduced by the body's own antioxidant system to maintain an oxidative balance.

Glutathione, the most abundant and important antioxidant in the body, is a tripeptide synthesized from the amino acids L-cysteine, L-glutamic acid and glycine (20). Glutathione plays a crucial role in antioxidant defense, nutrient metabolism and the regulation of pathways essential for the body's homeostasis (21).

In addition, glutathione serves as a regulatory compound in the activation of lymphocytes of the immune system (22).

It is evident that glutathione is a crucial compound for maintaining health and a deficiency of glutathione has been linked to numerous pathological conditions including cancer, neurodegenerative disorders, cystic fibrosis, HIV and aging (23). Glutathione is of particular interest to athletes as glutathione concentrations vary greatly as a result of dietary restrictions, training and oxidative stress.

The immense physical demands of sport expose the athlete's body to a high level of physiological stress. Glutathione plays a crucial role in maintaining a normal redox status during exercise (24, 25). Furthermore, it has been shown that exhaustive exercise reduces glutathione status (24, 25, 26).

This points to the need for increased glutathione levels in athletes. Scientists have shown that the amino acid cysteine is the rate-limiting factor in glutathione synthesis (27, 28). For this reason, the inclusion of a cysteine-rich protein source in the diet may prove effective in increasing the rate of glutathione resynthesis through the availability of sufficient amounts of cysteine in the amino acid pool.

However, supplementation with free cysteine is not recommended as it is spontaneously oxidized and such supplementation has been shown to be toxic (29). Dietary sources of cysteine in the form of cystine (two cysteine molecules linked by a disulfide bond) are more stable than free cysteine and are digested correctly. Whey protein supplements, including whey protein isolate and whey protein concentrate, are rich in cysteine and deliver cysteine to the body's cells via normal metabolic pathways (30, 31).

By providing a sufficient amount of cysteine, whey protein supplementation allows cells to synthesize glutathione and replenish glutathione reserves without undesirable side effects (31). (Thus, whey protein supplementation may serve to increase endogenous production of glutathione and alleviate oxidative stress in athletes).

The use of whey protein supplementation to alleviate exercise-induced decreases in blood glutathione levels has been extensively studied. Research has shown that whey protein supplementation is helpful in maintaining normal physiologic glutathione levels in athletic and non-athletic populations in response to exercise (32-24).

In addition, scientific research has shown that whey protein improves an athlete's ability to cope with acute oxidative stress and whey protein may therefore serve as a safe and effective alternative source of antioxidants for the prevention of sports injuries and illnesses caused by excessive levels of reactive oxygen species (35).

The research regarding whey protein supplements and glutathione status supports the use of whey protein to improve health status in athletes by enhancing the endogenous antioxidant system.

Whey protein and immune function

Strenuous exercise and heavy training programs have been associated with suppression of immune cell function (36-40). In addition, an inadequate or inappropriate diet can exacerbate the negative impact of heavy exercise on immune function. Suppression of immune function exposes the individual to an increased risk of infection.

Athletes increase both the volume and intensity of their training during certain phases of the season, which can result in a state of overreaching or overtraining. Recent research suggests that immune function is indeed sensitive to increases in training volume and intensity.

Although these studies have not shown that athletes are clinically immunocompromised during these periods of suppressed immune function, this condition may still be sufficient to increase the risk of widespread infections.

Since the components of the immune system are highly dependent on amino acids, endogenous and dietary amino acids can influence the status of the immune system.

Scientific research shows that whey protein is unique compared to other protein sources in its ability to promote strong immune function via numerous beneficial compounds including glutamine, α-lactalbumin and β-lactoglobulin and small protein fractions such as serum proteins, lactoferrin and a range of immunoglobulins (41 - 43).

Whey protein and the health of the digestive tract

Intense exercise leads to reduced blood flow to the internal organs, reduced blood flow to the digestive tract and increased temperatures in the gut (4). Reduced blood flow to the intestine and high temperatures in the intestine during exercise can lead to intestinal barrier dysfunction due to increased permeability of the impermeable junctions (5, 8).

This increased permeability of the intestinal wall leads to an invasion of gram-negative intestinal bacteria and/or their toxic components (endotoxins) into the blood circulation (45 - 47). Endotoxins are highly toxic lipopolysaccharides of the outer cell wall of gram-negative bacteria. Lipopolysaccharides are a primary trigger for an immune response in vivo via induction of the cytokine network (45). (Jeukendrup, et al., 2000).

This process, known as enditomexia, may result in increased susceptibility to infection and autoimmune disease due to absorption of pathogens/toxins into the bloodstream and tissues (48).

The research area of gut wall permeability is still relatively new and prospective long-term studies have yet to identify the potential health risks of chronic low-grade gut wall permeability.

However, recent studies have established a link between gut wall permeability and a number of autoimmune diseases including Chron's disease, Hashimoto's disease, lupus erythematosis, psoriasis and rheumatoid arthritis (49 - 53). In addition, gut wall permeability has been linked to mental illnesses including schizophrenia and depression (54, 55).

As previously mentioned, impermeable compounds are a major component of intestinal barrier function, acting as a physical and functional barrier against paracellular penetration by macromolecules from the lumen (56, 57). Therefore, regulating the permeability of impermeable compounds is critical for maintaining integrity and reducing the entry of endotoxins into the body.

The amino acid glutamine is critical for maintaining these impermeable junctions (56). Glutamine is the most abundant amino acid in the blood and is considered a conditionally essential amino acid (56). Under normal circumstances, glutamine is produced by the body in sufficient quantities to maintain normal physiological functions.

In stressful situations such as physical training, endogenous glutamine production may be insufficient, so the body must rely on exogenous (externally supplied) sources of glutamine to meet its needs.

Glutamine supplementation has been shown to normalize the permeability of the intestinal wall, which has been compromised by a number of physiological stressors, by restoring the integrity of impermeable junctions (58-60). In addition, glutamine supplementation has been shown to be effective in reducing exercise-induced increased intestinal wall permeability (61).

Whey protein is a rich source of glutamine and researchers have shown that whey protein supplementation is able to reduce increased intestinal wall permeability (62, 63). Therefore, whey protein may be useful in reducing exercise-induced increased intestinal wall permeability and the risk of endotoxemia and autoimmune disorders.

Summary

Whey protein is an excellent source of a wide range of amino acids and additional nutrients that have a beneficial effect on health. Whey protein has been shown to increase lean body mass, improve glutathione status, have immunomodulatory effects and improve digestive health when combined with resistance training.

A healthy and balanced diet can be enhanced with whey protein either through whole food sources or occasional use of whey protein supplements.

How and when should you use whey protein?

There are no hard and fast rules for how and when you should use whey protein, as whey protein is essentially a food product, just like cheese and yogurt. However, there are some smart ways to use whey protein!

Whey protein is often used post-workout as it is quickly digested and has been shown to promote muscle protein synthesis and inhibit post-workout muscle protein breakdown. The typical amount consumed after training is between 20 and 40 grams.

You can achieve the same effect with lower doses, but these do not appear to maximize this effect and more than 40 grams will not significantly increase this effect. You can consume your whey protein mixed with water or milk after training. You can also prepare it with frozen fruit as a smoothie or add it to other foods to increase the protein content of your post-workout meal.

Whey protein can also be used as a protein source for a meal or as an on-the-go snack. For example, if you mix whey protein into your oatmeal in the morning, you can increase the protein content of your breakfast or you can take whey protein to work and drink it as a snack.

Side effects of whey protein

Whey protein can have a number of minor digestive side effects including constipation, bloating and a bloated feeling. People who are allergic to milk protein may experience allergic reactions after consuming whey protein and should therefore consult their doctor before consuming whey protein or if they experience any signs of allergic reactions.

As the lactose content of whey protein varies from product to product, people who suffer from lactose intolerance may experience intolerance symptoms. These people should use a high-quality isolate with the lowest possible lactose/carbohydrate content or avoid whey protein altogether.

Foods that contain whey protein

Dairy products such as milk, cheese, butter and yogurt contain whey protein. (Fun fact: the liquid that collects on a yogurt contains whey protein - so don't pour your gains down the sink!)

Whey protein is also used in the manufacture of industrially produced food products as it is a very versatile ingredient. It is often used as an emulsifier in baked products, in ice cream mixes and in dressings. It is also used to improve the solubility of preparations and can also be found in frozen desserts and even soups and sauces.

Typically, the amount contained in these products will not help you build muscle mass, but whey protein is almost certainly included.

Other protein sources compared to whey protein

Soy protein

Soyprotein is a protein source that is made from soybeans. The ability of soy protein to provide amino acids to the body's amino acid pool is well documented and it is considered a fast digesting protein. In addition, soy protein has been shown to increase muscle protein synthesis more than a placebo.

Unfortunately, soy protein appears to be an inferior protein source compared to whey protein. For example, consumption of 30 grams of whey protein or soy protein resulted in equivalent p70S6K phosphorylation (a molecule involved in protein synthesis) 2 hours after exercise, but soy protein, unlike whey protein, failed to maintain long-lasting phosphorylation of p70S6K for up to 4 hours after exercise.

In another study, the thermic effect of whey protein was 14.54% higher than that of soy protein, suggesting that whey protein is more suitable for weight loss. In the same study, the average maximum oxygen uptake was 29.94% for whey protein and only 23.98% for soy protein. Soy protein appears to be faster to digest, but may be inferior in terms of muscle protein synthesis.

Casein

Milk protein consists of whey protein and casein protein. Casein is often considered the "other" protein. Like whey protein, casein is a rich source of amino acids and provides a biologically complete amino acid profile.

Casein is digested more slowly than whey protein and therefore releases amino acids into the bloodstream over a longer period of time. This has led to the hypothesis that casein may be superior for muscle building as it provides a longer supply of amino acids, which is particularly useful when used in the evening before going to bed.

Although there are substantial claims regarding the superiority of casein, these do not stand up to closer scientific scrutiny. What we can really rely on, however, is that casein is probably a better choice than whey protein before going to bed, whereas whey protein is probably better after training.

From a weight loss perspective, casein may have a slight, albeit indirect, edge over whey protein. A potential advantage of casein over whey protein is that casein has a better satiating effect. As it is slower to digest, it often results in longer lasting satiety after consumption. This could help to reduce overall calorie intake and promote fat loss better than whey protein.

Whey protein compared to other types of protein

The two most popular methods for determining the quality/efficiency of a protein source are the biological value (BV) and the Protein Digestibility corrected Amino Acid Score (PDCAAS). Biological value refers to a practical measurement that determines the degree to which an animal is able to utilize the protein in question. It is calculated by analyzing nitrogen retention after consumption of the protein being tested.

The PDCAAS is a number between 0 and 1 and evaluates the protein quality based on its amino acid content relative to the human requirement for these amino acids. Basically, the higher the biological value or PCDAAS of a protein source, the better it can be used by the animal (yes, we humans are animals too). The table below gives an overview of the biological value and PDCAAS of various widely used protein sources:

Protein sources
Protein	BV	PDCAAS
Whey protein concentrates and isolates	104 to 159	1,00
Whole egg	100	1,00
Milk	91	1,00
Egg white	88	1,00
Cottage cheese	84	1,00
Tuna	83	?
fish	82	?
Beef	80	0,92
Chicken	79	?
Soy	74	0,91
Casein	71	1,00
Peanuts	68	0,52
Yoghurt	68	?
Oat flakes	58	0,57
Wheat	54	0,42

FAQ

How much whey protein should I use?

There is no real guideline for how much whey protein you should consume. Having said that, there are a few things you should consider. There seems to be a good case for aiming for 20 to 30 grams of whey protein post-workout to improve the muscle growth response after training. Some people will need more or less whey protein to optimize this, but there is no set value. The optimal amount will always depend on the type of protein, as the leucine content of the protein will determine the muscle growth response.

In the context of daily consumption, it would be wise to use whey protein as a supplement and not to cover the entire daily protein requirement with whey protein. 1 to 2 servings of whey protein per day would be a general guideline.

I suffer from lactose intolerance. Can I still use a whey protein supplement?

The degree of gastrointestinal reactions to whey protein can vary greatly from person to person. Typically, whey protein isolate contains the least amount of lactose and therefore has a lower likelihood of a person with any digestive discomfort reacting to this protein source. If you are unable to find a whey protein that is suitable for your individual lactose intolerance, then rice protein may be the next best alternative for you.

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

The type of allergy to milk and the degree of allergic reaction to milk varies from allergy sufferer to allergy sufferer. If you are allergic to the milk proteins, then you may be able to consume hydrolyzed whey protein or pure whey protein isolate as this removes many of the allergenic compounds.

If you are lactose intolerant, you can try whey protein isolate, which is often virtually lactose free and is not a problem for many people who are lactose intolerant. It is of course wise to consult your doctor first and consume small portions of whey protein isolate or hydrolyzed whey protein and observe how your body reacts to it.

Is it true that whey protein is bad for the kidneys?

There is no scientific evidence that whey protein has any measurable negative effect on the kidneys in healthy people who have no history of kidney disease and have normal kidney function.

Is it true that whey protein is bad for my bones?

This is a good question. One of the most common arguments against high-protein diets - specifically high-protein diets that include a lot of animal protein - is that they are devastating to bone health. So let's take a look at what science has to say on the subject.

Did you know that high-protein diets increase calcium absorption in the digestive tract and that there is ample evidence to support the hypothesis that the increased intestinal calcium absorption of high-protein diets may actually improve bone health?

In a recently published paper by the leading scientists in the field of protein and bone health, the authors conclude "Recent epidemiologic, isotopic, and meta-analysis studies suggest that dietary protein synergistically interacts with calcium to improve calcium retention and bone metabolism.

The recommendation to reduce dietary protein intake to improve bone health is unwarranted and even potentially dangerous for individuals who consume inadequate amounts of protein." (64).

I think the idea that high-protein diets have a negative impact on bone health due to the net acid load has been adequately refuted. High-protein diets are not only safe for bone health, but may actually be very beneficial, especially for the elderly and those at risk for osteoporosis.

This has been my somewhat long-winded way of saying that whey protein is actually good for your bones!

Can I combine whey protein supplements with my other supplements in powder form such as creatine, glutamine, etc.?

Of course! You can mix creatine with your whey protein, whereas adding glutamine would be something of an overkill, as whey protein already contains a substantial amount of glutamine. Powdered greens are also an excellent addition, providing additional micronutrients.

Does it matter what liquid I use to mix my whey protein with?

Yes and no. The liquid will change the composition and texture of your shake. Water often results in a very thin shake, whereas milk makes the shake thicker and creamier.

From an absorption perspective, it could be argued that consuming whey protein with milk or other carbohydrates and sodium could increase the rate of absorption, but this is unlikely to make a large or even noticeable difference to the total amount of protein absorbed and its impact on muscle protein synthesis.

Does cooking or baking denature protein?

Yes, cooking or baking denatures the protein. However, this has virtually no effect on the muscle building capacity of the protein as this lies in the amino acids themselves. The denaturation process may reduce some of the bioactivity of the other components of whey protein, but this is not something worth worrying too much about.

Are there any dangers associated with consuming whey protein?

There are a few dangers associated with taking whey protein. The first is an allergic reaction to milk-based proteins. Some people are allergic to milk protein and these people may experience allergic reactions to whey protein.

There are also potential dangers if a whey protein is used from a non-reputable source or a company with poor quality control. Like any food product, whey protein can pose dangers if it is poorly manufactured or processed. However, these potential dangers are so insignificant that for most people the potential benefits far outweigh the risks.

Is whey protein safe for teenagers?

Based on the data currently available (and there is an almost obscene amount of research done on whey protein), there is no evidence that whey protein could be harmful to teenagers. It may even be beneficial for teenagers, as many of the components of whey protein support the body's growth.

Should women use whey protein differently to men?

There is no real reason why women should use whey protein differently to men. As women often weigh less than men, they may have a lower total daily protein requirement, which means they may need slightly less whey protein, but there are no specific needs for women in terms of how and when they should consume whey protein.

Should I only use whey protein isolate as it contains the highest amount of protein?

Whey protein isolate does indeed have the highest purity and the highest amount of protein per serving, making it an excellent choice for muscle building.

However, the production of whey protein isolate also filters out some of the other important bioactive compounds such as alpha-lactalbumin, beta-lactalbumin, immunoglobulins, glycomacropeptides and lactoferrin, to name but a few. So it might be a good idea to integrate both whey protein isolate and whey protein concentrate into your supplement program.

References

1. Burke, D. G., Chilibeck, P., Davison, K., & Candow, D. (2001). The effect of whey protein supplementation with and without creatine monohydrate combine with resistance training on lean tissue mass and muscle strength. International Journal of Sport Nutrition and Exercise Metabolism, 11, 349-364.
2. Coburn, J. W., Housh, D., Malek, M., Beck, T., Cramer, J., Johnson, G., et al. (2006). Effects of leucine and whey protein supplementation during eight weeks of unilateral resistance training. Journal of Strength and Conditioning Research, 20 (2), 284-291.
3. Frestedt, J. L., Zenk, J., Kuskowski, M., Ward, L., & Bastian, E. (2008). A whey-protein supplement increases fat loss and spares lean muscle in obese subjects: A randomized human clinical study . Nutrition & Metabolism , 5 (8), 1-7.
4. Willoughby, D. S., Stout, J., & Wilborn, C. (2007). Effects of resistance training and protein plus amino acid supplementation on muscle anabolism, mass, and strength. Amino Acids , 32 (4), 467-477.
5. Lambert, G. P. (2009). Stress-induced gastrointestinal barrier dysfunction and its inflammatory effects. Journal of Animal Science , 87 (E. Supplement), E101-E108.
6. Low, P. L., Rutherfurd, K., Gill, H., & Cross, M. (2003). Effect of dietary whey protein concentrate on primary and secondary antibody responses in immunized BALB/c mice . International Immunopharmacology , 3 (3), 393-401.
7. Micke, P., Beeh, K., Schlaak, J., & Buhl, R. (2001). Oral supplementation with whey proteins increases plasma glutathione levels of HIV-infected patients. European Journal of Clinical Investigation , 31 (2), 171-178.
8. Pals, K. L., Chang, R., Ryan, A., & Gisolfi, C. (1997). Effect of running intensity on intestinal permeability. Journal of Applied Physiology , 82, 571-576.
9. Hulmi, J. J., Lockwood, C., & Stout, J. (2010). Effect of protein/essential amino acids and resistance training on skeletal muscle hypertrophy: A case for whey protein . Nutrition & Metabolism , 7 (51).
10. Dickinson, J. M., & Rasmussen, B. (2011). Essential amino acid sensing, signaling, and transport in the regulation of human muscle protein metabolism. Current Opinion in Clinical Nutrition & Metabolic Care , 14 (1), 83-88.
11. Li, J. B., & Jefferson, L. (1978). Influence of amino acid availability on protein turnover in perfused skeletal muscle .Biochimica et Biophysica Acta , 544 (2), 351-359.
12. Esmarck, B., Andersen, J., Olsen, S., Richter, E., Mizuno, M., & Kjaer, M. (2001). 18. timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. Journal of Physiology , 535, 301-311.
13. Cribb, P. J., Williams, A., Carey, M., & Hayes, A. (2006). The effect of whey isolate and resistance training on strength, body composition, and plasma glutamine. International Journal of Sports Nutrition and Exercise Metabolism, 16 (5), 494-509.
14. Buckley, J. D., Thomson, R., Coates, A., Howe, P., DeNichilo, M., & Rowney, M. (2010). Supplementation with a whey protein hydrolysate enhances recovery of muscle force-generating capacity following eccentric exercise . Journal of Science in Medicine and Sport, 13, 178-181.
15. Tipton, K. D., Elliot, T., Cree, M., Wolf, S., Sanford, A., & Wolf, R. (2004). Ingestions of casein and whey proteins result in muscle anabolism after resistance exercise. Medicine and Science in Sports and Exercise, 36, 2073-2081.
16. Hulmi, J. J., Tannerstedt, J., Selanne, H., Kainulainen, H., Kovanen, V., & Mero, A. (2009). Resistance exercise with whey protein ingestion affects mTOR signaling pathway and myostatin in men. Journal of Applied Physiology, 106, 1720-1729.
17. Sachdev, S., & Davies, K. (2008). Production, detection, and adaptive responses to free radicals during exercise. Free Radical Biology & Medicine, 44 (2), 215-223.
18. Adams, A. K., & Best, T. (2002). The role of antioxidant in exercise and disease prevention. The Physician and Sports Medicine, 30 (5), 2002.
19. Lowery, L. (2001). Antioxidants supplements and exercise. In J. Antonio, & J. Stout (Eds.), Sport Supplements (pp. 260-278). Philidelphia, PA: Lippincott, Williams and Wilkins.
20. Thomas, J. A. (1999). Oxidative stress and oxidant defense. In M. Shils, J. Olson, M. Shike, & A. Ross (Eds.), Modern Nutrition in Health and Disease (pp. 751-782). Baltimore, MD: Lippincott Williams & Wilkins.
21. Wu, G., Fang, Y., Yan, S., Lupton, J., & Turner, N. (2004). Glutathione metabolism and its implications for health.Journal of Nutrition, 134, 489-492.
22. Droge, W. (1996). Modulation of the immune response by cysteine and cysteine derivatives. Italian Society for Parenteral and Enteral Nutrition, 14, 1-4.
23. Townsend, D. M., Tew, K., & Tapiero, H. (2003). The importance of glutathione in human disease. Biomedicine & Pharmacotherapy, 57, 145-155.
24. Li, J. J., & Fu, R. (1992). Responses of glutahtione system and antioxidant enzymes to exhaustive exercise and hydroperoxide. Journal of Applied Physiology, 72 (2), 549-554.
25. Kerksick, C., & Willoughby, D. (2005). The antioxidant role of glutathione and n-acetyl-cysteine supplements and exercise-induced oxidative stress. Journal of the International Society of Sports Nutrition, 2 (2), 38-44.
26. Gohil, K., Viguie, C., Stanley, W., Brooks, G., & Packer, L. (1988). Blood glutathione oxidation during human exercise. Journal of Applied Physiology, 64 (1), 115-119.
27. Lyons, J., Rauh-Pfeiffer, A., Yu, Y., Lu, X., Zurakowski, D., Tompkins, R., et al. (2000). Glood glutathione synthesis rates in health adults receiving a sulfur amino acid-free diet. Proceedings of the National Academy of Sciences of the United States of America, 97 (10), 5071-5076.
28. Rathbun, W. B., & Murray, D. (1991). Age-related cysteine uptake as rate-limiting in glutathione synthesis and glutathione half-life in the cultured human lens. Experimental Eye Research, 53 (2), 205-212.
29. Meister, A. (1984). New aspects of glutathione biochemisty and transport selective alterations of glutathione metabolism. Nutrition Reviews, 42, 397-410.
30. Chitapanarux, T., Tienboon, P., Pojchamarnwiputh, S., & Leelarungrayub, D. (2009). Open-labeled pilot study of cysteine-rich whey protein isolate supplementation for nonalchoic steatohepatitis patients. Hepatology , 24, 1045-1050.
31. Sindayikengera, S., & Xia, W. (2006). Nutritional evaluation of caseins and whey proteins and their hydrolysates from Protamex. Journal of Zhejian University Science B , 7 (2), 90-98.
32. Mariotti, F., Simbelie, K., Makarious-Lahham, L., Huneau, J., Laplaize, B., Tome, D., et al. (2004). Acute ingestion of dietary proteins improves post-exercise liver glutathione in rats in a dose-dependent relationship with their cysteine content. Journal of Nutrition , 134, 128-131.
33. Middleton, N., Jelen, P., & Bell, G. (2004). Whole blood and mononuclear cell glutathione response to dietary whey protein supplementation and trained male subjects. International Journal of Food Science Nutrition , 55 (2), 131-141.
34. Vatani, D. S., & Golzar, F. (2012). Changes in antioxidant status and cardiovascular risk factors of overweight young men after six weeks supplementation of whey protein isolate and resistance training. Appetite , 59, 673-678.
35. Xu, R., Liu, N., Xu, X., & Kong, B. (2011). Antioxidative effects of whey protein on peroxide-induced cytotoxicity.Journal of Dairy Science , 94 (8), 3739-3746.
36. Gleeson, M. (2007). Immune function in sport and exercise. Journal of Applied Physiology , 103, 693-699.
37. Gleeson, M., McDonald, W., Cripps, A., Pyne, D., Clancy, R., & Fricker, P. (1995). The effect on immunity of long-term intensive training in elite swimmers . Clinical & Experimental Immunology , 102 (1), 210-216.
38. Baj, Z., Kantorski, J., Majewska, E., Zeman, K., Pokoca, L., Fornalczyk, E., et al. (1994). Immunological status of competitive cyclists before and after the training season. International Journal of Sports Medicine , 15 (6), 319-324.
39. Bury, T., Marechal, R., Mahieu, P., & Pirnay, F. (1998). Immunological status of competitive football players during the training season. International Journal of Sports Medicine , 19 (5), 364-368.
40. Shepard, R. J., Rhind, S., & Shek, P. (1994). Exercise and the immune system. Natural killer cells, interleukins and related responses. Sports Medicine , 18 (5), 340-369.
41. Cribb, P. J. (2005). U.S. whey proteins in sports nutrition. U.S. Dairy Export Council.
42. Cribbs, P. J. (2004). Whey proteins and immunity. U.S. Dairy Export Council.
43. Walzem, R. M., Dillard, C., & German, J. (2002). Whey components: millennia of evolution create functionalities for mammalian nutrition: What we know and what we may be overlooking. Critical Reviews in Food Science and Nutrition , 42 (4), 353-375.
44. Qarnar, M. I., & Read, A. (1987). Effects of exercise on mesenteric blood flow in man. Gut , 28, 583-587.
45. Jeukendrup, A. E., Vet-Joop, K., Sturk, A., Stegen, J., Senden, J., Saris, W., et al. (2000). Relationship between gastro-intestinal complaints and endotoxaemia, cytokine release and the acute-phase reaction during and after a long-distance triathlon in highly trained men. Clinical Science , 98, 47-55.
46. Lambert, G. P. (2008). Intestinal barrier dysfunction, endotoxemiz, and gastrointestinal symptoms: the 'canart in the coal mine' during exercise-heat stress? Medicine and Sport Science , 53, 61-73.
47. Van Deventer, S. J., & Gouma, D. (1994). Bacterial translocation and endotoxin transmigration in intestinal ischaemia and reperfusion. Current Opinions in Anaesthiology , 7, 126-130.
48. Lamprecht, M., Bogner, S., Schippinger, G., Steinbauer, K., Fankhauser, F., Hallstroem, S., et al. (2012). Probiotic supplementation affects markers of intestinal barrier, oxidation, and inflammation in trained men; a randomized, double-blinded, placebo-controlled trial . Journal of the International Society of Sports Nutrition , 9 (45), 1-13.
49. Sasso, F. C., Carbonara, O., Torella, R., Mezzogiomo, A., Esposito, V., deMagistris, L., et al. (2004). Ultrastructural changes in enterocytes in subjects with Hashimoto's thyroiditis . Gut , 53 (12), 1878-1880.
50. Caradonna, L., Amati, L., Magrone, T., Pellegrino, N., Jirillo, E., & Cacavvo, D. (2000). Invited review: Enteric bacteria, lipopolysaccharides and related cytokines in inflammatory bowel disease: biological and clinical significance .Journal of the International Endotoxin Innate Immunity , 6 (3), 205-214 .
51. Apperloo-Renkema, H. Z., Bootsma, H., Mulder, B., Kallenberg, C., & van der Waajj, D. (1994). Host-microflora interaction in systemic lupus erythematosus (SLE): colonization resistance of the indigenous bacteria of the intestinal tract. . Epidemiiology and Infection , 112 (2), 367-373.
52. Hamilton, I., Fairris, G., Rothwell, J., Cunliffe, W., Dixon, M., & Axon, A. (1985). Small intestinal permeability in dermatological disease. QJM , 56, 559-567.
53. Smith, M. D., Gibson, R., & Brooks, P. (1985). Abnormal bowel permeability in ankylosing spondylitis and rheumatoid arthritis. The Journal of Rheumatology , 12 (2), 299-305.
54. Wood, N. C., Hamilton, I., Axon, A., Khan, S., Quirke, P., Mindham, R., et al. (1987). Abnormal intestinal permeability. An aetiological factor in chronic psychiatric disorders? . The British Journal of Psychiatry , 150, 853-856.
55. Maes, M., Kubera, M., & Leunis, J. (2008). The gut-brain barrier in major depression: Intestinal mucosal dysfunction with an increased translocation of LPS from gram negative enterobacteria (leaky gut) plays a role in the inflammatory pathophysiology of depression. Neuroendocrinology Letters , 29 (1), 117-124.
56. Rao, R. K., & Samak, G. (2012). Role of glutamine in protection of intestinal epithelial tight junctions. Journal of epithelial biology and pharmacology , 5, 47-54.
57. Mitic, L. L., & Anderson, I. (1998). Molecular architecture of tight junctions. Annual Review of Physiology , 60, 121-142.
58. Wilmore, D. W., Smith, R., O'Dwyer, S., Jacobs, D., Ziegler, T., & Wang, X. (1988). The gut: A central organ after surgical stress. Surgery , 104, 917-923.
59. Peng, X., Yan, H., You, Z., Wang, P., & Wang, S. (2004). Effects of enteral supplementation with glutamine granules on intesinal mucosal barrier function in severely burned patients. Burns , 30, 135-139.
60. Kozar, R. A., Schultz, S., Bick, R., Poindexter, B., DeSoignie, R., & Moore, F. (2004). Enteral glutamine not but alanine maintains small bowel barrier function after ischemia/reperfusion injury in rates. Shock , 21, 433-437.
61. Hoffman, J. R., Ratamess, N., Kang, J., Rashti, S., KElly, N., Gonzalez, M., et al. (2010). Examination of the efficacy of acute L-alanyl-L-glutamine ingestion during hydration stress in endurance exercise . Journal of the International Society of Sports Nutrition , 7 (8).
62. Kotler, B. M., Kerstetter, J., & Insogna, K. (2013). Claudins, dietary milk proteins, and intestinal barrier regulation.Nutrition Reviews , 71 (1), 60-65.
63. Benjamin, J., Makharia, G., Ahuja, V., Rajan, K. D., Kalaivani, M., Gupta, S. D., et al. (2012). Glutamine and whey protein improve intestinal permeability and morphology in patients with Chron's disease: A randomized controlled trial. Digestive Diseases and Sciences, 57 (4), 1000-1012.
64. Kerstetter, J., Kenny, A., Insogna, K. Dietary protein and skeletal health: a review of recent human research. (2011). Current Opinions in Lipidology. 22(1), 16-20.

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