Whey Protein

Whey is one of two protein fragments of dairy protein, the other being casein. Whereas casein consists of approximately 70-80% of bovine protein, whey protein makes up the remaining 20-30%. Whey is the water-soluble fragment, and is extracted from casein during the process of coagulation and syneresis (explained on the casein processing page, the two fragments separate after a coagulant is added). Whey is the liquid portion that is seen as 'by-product' from the process of making cheese that consists of mostly caseins, and the technical definition of the whey is "the group of milk proteins that remain soluble in milk serum or whey after precipitation of CN at pH 4.6 and 20°C".^[6] Thus 'Whey' is not one protein but a class of proteins grouped collectively based on their solubility and production method.

Whey can be found in milk in general. Although the majority of commercially sold whey is derived from cows (bovine whey), whey can also be derived via any animal that produces milk through breast tissues: buffalo,^[7] camels,^[8] llamas,^[9] kitties,^[10] and humans^[11] to name a few.

When milk is met with a coagulating agent, the part that coagulates is cheese; the part that does not (liquid part) are the wheys. The phrase "The curds and the wheys" refer to this process, and the curds are mostly casein proteins while the wheys are whey protein

The amino acids in whey protein can be formed into different orders, and create unique bioactive peptides. Beyond differences in amino acid composition, different protein sources can have different effects through their bioactive peptides. The peptides in whey are the following, and the four (4) bolded peptides are those with most practical relevance (due to their high contents in whey).

• β-Lactoglobulin (A and B) with about two-fold more A than B, 1290mg and 2280mg per liter of whey^[12] and 2-4g (combined A and B) per liter of milk^[6] β-Lactoglobulin is the major bioactive peptide in whey, and the B fragment is a 162 amino acid sequence with a molecular weight of 18,227kDa and is leucine rich (13.5%); A is the other most well known variant, but β-Lactoglobulin has recently been shown to possess H,^[13] I and J,^[14] and W variants^[15] β-Lactoglobulin has the ability to bind fat soluble and amphiphilic molecules and can enhance absorption of fat soluble nutrients^[6] This protein itself is approximately a quarter (25.1%) Branched Chain Amino Acids and, along with Bovine Serum Albumin, may aid in hydrophobic (fat-soluble) nutrient uptake^[16]

• Alpha-Lactalbumin, at about 0.6-1.7g per litre of whole milk^[6] with more precise estimates at 1.2-1.5g per liter of whey.^[6] Alpha-Lactalbumin is a 123 amino acid sequence with two variants (A and B) and the reference variant (B) is high in all Leucine (10.6%), Aspartic Acid (10.6%) and Cysteine (6.5%) and has a molecular weight of 14,178kDa.^[6] It is seen as good nutrition for infants due to having 72% homology to human alpha-lactalbumin, a nutrient found in breast milk^[17]

• Bovine Serum Albumin (BSA), which is at about 0.4g per liter of milk.^[6] This is about 1.5% of total milk proteins, but due to its lack of occurrence in casein protein it shoots up to 8% of total whey proteins. It is the largest protein in whey at 583 amino acids with a molecular weight of 66,399kDa^[18] that, when in the pH range of 4.5-8, forms a heart shaped molecule.^[19] BSA allows binding to hydrophobic molecules, and can potentially increase uptake of fat-soluble (hydrophobic) molecules^[16]

• Immunoglobulins, which comprises 1% of total milk protein but is elevated to 8% of total whey proteins. A category of small Y-shaped proteins (4 peptide chains) bound by disulfide bonds, with the (2) light chains weighing approximately 22.5-27.3kDa each.^[6] There are a variety of immunoglobulins in whey (IgGI, IgG2a(A1 and A2), IgG2b and IgG3; IgA, M, E, and D). One immunoglobulin classified as β₂-microglobulin is also referred to as lactollin.^[6] Due to these immunoglobulins being small in size and bound by disulfide chains, they are whey protein's largest source of the amino acid Cysteine (to induce glutathione synthesis) and can interact with the immune system

• Glycomacropeptides (GMPs) that are technically casein proteins but are lost into the liquid whey during separation (stage of processing); GMPs are researched for their interactions with hunger and the hormone Cholecystokinin (CCK).^[20][21][22] GMPs are one of the bioactives investigated for the ability of whey to suppress appetite^[23]

• Lactoferrin, an iron-binding peptide with thrice the affinity relative to transferrin^[24] that has anti-cancer effects;^[25] present at around 56-164mcg/mL when diluted at 1:10 for analytic purposes.^[26] This gives a concentration of 0.56-1.64mg/g whey protein (concentrate), or about 0.5-1.6% by weight of whey; 0.02-0.1g per liter of whole milk^[6] It is 689 amino acids in length, and equally high in leucine (9.58%) and alanine (9.72%)

• Lactoperoxidase

• NOP-47, a nitric oxide dependent quaternary protein that has been shown to increase blood flow^[27][28]

• Lactostatin (Ile-Ile-Ala-Glu-Lys) produced from β-Lactoglobulin^[29]

Amino acids in whey are grouped into protein structures or float as 'free' amino acids. Those that are grouped as protein structures are 'peptides' and may have unique properties based on the sequence (order) of amino acids that make them up. Bioactive peptides in whey are one of the two possible reasons for differences between protein sources (the other being total amino acid composition)

The bioactive peptides in whey (strings of small-chained amino acids that are left over when larger proteins are digested) tend to be more involved with immunity when compared to other protein sources, mostly through the immunoglobulins and other large proteins

All of the aforementioned peptides are constructed from a collection of amino acids, and the amino acid profile of whey can confer some benefit after bioactive peptides are digested. The numbers below are averaged from multiples sources found here for Whey Protein Concentrate.^[30][31]

• Isoleucine at 49.7-57.3mg/g

• Leucine at 79.8-106.6mg/g

• Valine at 18.4-59.3mg/g

• Lysine at 76.1-88.1mg/g

• Methionine and Cysteine (Sulfur containing) at 79.7mg/g combined, approximately equal ratios

• Phenylalanine and Tyrosine (Aromatic) at 58.2mg/g combined, approximately equal ratios

• Threonine at 61.1-68.7mg/g

• Tryptophan at 17.3mg/g

• Histidine at 7.8-18.7mg/g

• Alanine at 42.1-55.5mg/g

• Arginine at 22.0-27.1mg/g

• Glutamine at 141.4-158.4mg/g

• Glycine at 13.8-53.2mg/g

• Proline at 46.7-66.6mg/g

• Serine at 38.8-53mg/g

• Aspartic Acid at 94.1mg/g

During the process of hydrolysis, the composition of some amino acids change. At 5% hydrolysis the levels of Sulfur containing amino acids drop from 79.7mg/g to 40.7mg/g and stabilize in that range until 20% hydrolysis (the highest tested hydrolysis level in this study). Differing trends are also seen with Glycine, which drops from 53.2mg/g to 19.1mg/g; Valine, which spikes from 18.4mg/g to 53.5%, and Histidine which rises from 7.8mg/g to 17.8mg/g. All other amino acids tend to fluctuate around their normal levels, and this study used an enzymatic hydrolysis via Protamex (Bacillus proteinase, broad specificity for hydrophobic amino acids) at 1.5AU/g.^[30]

Some other molecules can be found in whey protein. These are commonly referred to as impurities if the person labeling them sees them as bad and as additions if no bias is attached. This list has things inherently included with the whey fraction of dairy, and excludes any additions that a company may add to their proprietary blends or personal Whey Protein products. Molecules that may be found in the Whey fraction that are not amino acids in nature are:

• Hippuric Acid at 22.4-23.1mg/kg in Rennet Whey (0.0023%)^[32]

• Orotic Acid at 74-75.5mg/kg in Rennet Whey (0.0075%)^[32]

• Possible microRNA (miRNA) with unknown bioactivity^[33]

• TGF-β₁ (Transforming Growth Factor-beta 1) in mostly human milk,^[34] but Bovine whey as well^[35]

Glutathione is an endogenous (made and stored in the body) anti-oxidant enzyme that is made of amino acids, with L-Cysteine being the rate-limiting enzyme.

Populations that may be deficient in glutathione levels and show promise with either whey or isolated L-Cysteine supplementation include cancer patients,^[36] patients with HIV infection,^[37][38] and the elderly (aging is associated with reduced glutathione synthesis, which can be reversed with L-Cysteine).^[39] Increased glutathione via whey protein supplementation has been associated with longevity in at least one study in mice, where Whey outperformed casein and promoted survival.^[40]

Some other conditions that are characterized by oxidative stress, but not specifically a glutathione deficiency, may also be implicated. These include Cystic Fibrosis^[41] of which supplementation of whey can increase glutathione stores.^[42][43]

Glutathione stores can be increased in otherwise healthy persons, with whey protein (in this study, pressurized whey) increasing glutathione by up to 24% in 2 weeks with approximately 2 regular scoops (45g) of protein daily.^[44] This increase is additive with the increase seen with resistance training.^[45]

Whey can be a convenient and cheap vessel of dietary L-Cysteine, which can be elevated to vitamin-like importance in certain conditions of oxidative stress. A cysteine deficiency is not universally recognized due to it being an non-essential amino acid (can be synthesized from methionine, an essential amino acid) but appears to have some manner of deficiency syndrome associated with it, at least indirectly via glutathione

Hydrogen Sulfide (H₂S) is a gaseous byproduct (frequently remarked to be the causative smell of eggs^[46]) that appears to act as a signalling molecule, similar to Nitric Oxide in the sense that it promotes vasorelaxation of blood vessels (although the mechanism is by stimulating K_ATP channels^[47][48]) and has anti-oxidative capabilities. A circulating H₂S pool of 10-100uM exists in the human body^[49][50] although higher (130uM) has been reported in healthy persons.^[51]

H₂S is produced endogenously mainly by the action of two enzymes, cystathionine-β-synthase and cystathionine-?-lyase.^[48] The former enzyme (cystathionine-β-synthase) is highly localized to the central and peripheral nervous system while the latter is expressed in the thoracic aorta, portal vein, ileum, heart, liver, kidney, and vascular smooth muscle.^[48][50] Two other enzymes may also contribute to a circulating H₂S pool, namely 3-mercaptopyruvate sulfurtransferase and cysteine aminotransferase, both of which are active in the brain and the endothelium.^[52][53][54] Abolishing cystathionine-?-lyase and reducing the circulating H₂S pool induce hypertension in rats and reduce the abilities of the blood vessels to respond to vasorelaxation^[50] as well as increasing homocysteine levels, indicative of heart and neurovascular diseases.^[55] Conversely, adding in a H₂S donor to increase circulating levels can, in ApoE deficient mice, reduce artherosclerotic build-up and promotes blood flow.^[56]

At the outset, H₂S (Hydrogen Sulfide) appears to be a heart healthy (cardioprotective) signalling molecule that is derived from a circulating Cysteine pool; Cysteine remains in storage in the body, and serves to buffer a pool of H₂S that preserves physiological functions

Circulating Hydrogen sulfide levels appear to be lower in Type II Diabetics (110uM) relative to age-matched non-diabetic controls (130uM) when weight was not measured,^[51] and are lower in non-diabetic obese persons relative to non-diabetic lean persons.^[57]

Theoretically, maintaining a sufficient Cysteine pool should be cardioprotective; some populations appear to be lower in H₂S but no evidence currently exists that supplementing Cystine in these populations can increase H₂S

Concentrate is the least processed form, and is 35-80% protein by weight.^[1] The wide range is applicable to all whey, as some is used in food products as well; supplemental whey protein concentrate is referred to as WPC 80 and tends to be standardized at 80% protein by weight.

Isolate is defined as being more than 90% protein by weight.^[1]

Hydrolysate is protein that is enzymatically and acid pretreated to reduce the particulate size even further and is the fastest absorbed. Hydrolyzed protein is protein that cleaves peptide bonds, and reduces large quaternary proteins down to peptides and free amino acids. Due to this, special bioactive effects of quaternary protein structures in whey (immunoglobulins, bovine serum albumin, lactalglobulin and lactalbumins) may not apply to hydrolyzed whey, depending on the di- and tripeptides left over.^[58] An excess of free amino acids, particularly the Branched Chain Amino Acids and Proline (the latter more of a concern to casein hydrolysate) can produce a large adverse bitter taste.

The process of hydrolyzation can reduce the allergic potential of whey and milk protein, due to removing allergenic epitopes; a reason for the usage of hydrolyzed proteins in infant formula^[58] which, according to meta-analysis and systemic reviews, is effective in reducing the occurrence of atopic dermatitis (an inflammatory condition) when compared against cows milk; although breast milk for infants is still advised.^[59][60][61] Hydrolysis, even partially, can improve the solubility and improve in vitro digestability.^[30]

In a study comparing the effects of whey protein hydrolysate to casein hydrolysate (a fast absorbed form of casein), whey protein resulted in more muscle protein synthesis over 8 hours after 20g in older individuals (74+/-1yrs) at rest.^[62] Whey hydrolysate had a mixed fractional protein synthesis rate of 0.15+/-0.02%, while casein hydrolysate and regular casein had 0.10+/-0.01% and 0.08+/-0.01% respectively.^[62] A correlation (r=0.55) was noted with plasma C_max values of essential amino acids, and a slightly higher correlation (r=0.66) with leucine in particular.^[62]

In instances where a faster protein source is desired (perhaps pre-fuel for fasted training, or protein synthesis in the elderly), then a hydrolyzed whey protein may confer additional benefits when compared to a whey concentrate. They have either equal health benefits, or hydrolysate may confer less (or at least different) health benefits due to breaking of large peptides prior to digestion

One study that gave participants Whey Isolate or Whey Hydrolysate and tested performance at baseline and then 6 hours later noted that only the Hydrolysate group recovered power in such a short time frame, although no differences existed in muscle soreness.^[63] Protein in general appears to enhance recovery, but most studies are done on subsequent days; this suggests Hydrolyzed Whey may be of benefit to two-a-day workouts.

Ultrafiltration is another filtration through a physical gradient, where whey passes through and smaller compounds are allowed to pass and larger molecules get caught.^[64] Standard ultrafiltration uses a transmembrane pressure (pressure used to 'push' molecules through the gradient) of 275kPa and tend to use polyethersulfone barriers, which allows molecules of 5-10kDA to pass.^[65] Bovine Serum Albumin, a-lactalbumin, and β-lactoglobulin are significantly larger than this and excluded, while most immunoglobulins are closer but still above this threshold. Exclusion of a-lactalbumin in the whey is actually a cost-effective way of isolating a-lactalbumin for usage in infant formulas, research, or for fortification purposes.^[65][66]

When Whey Concentrate is subject to ultrafiltration, the amount of vitamins per gram of protein increases slightly relative to the whey it was derived from. Amino acid ratios remain the same, but are much higher per gram of product due to the act of concentration. Mineral and ash content are reduced.^[67]

Microfiltration is the same process of ultrafiltration, but with a more restrictive gradient. Rather than a polyethersulfone barrier, microfiltration tends to use a polyvinylidene fluoride (PVDF) membrane which allows molecules between 0.1-0.5uM through, a more restrictive membrane relative to ultrafiltration.^[65]

Whey appears to resist coagulation in the stomach and pass on relatively quickly to the intestines.^[16] This is notable due to casein proteins (the other component of milk) emptying slower from the stomach,^[68] via precipitation in an acidic medium which slows gastric passage due to the solid inducing a duodenal 'lag phase'.^[69] Interestingly, enzymes found inherently in milk (Alkaline Phosphatase) can dephosphorylize casein and enhance solubility and gastric passage.^[70][71]

When measuring beta-lactalbumin (largest component of whey) in the intestines, this specific component does not appear to be subject to much hydrolysis in the stomach as it appears intact in the intestines.^[72] Due to lack of hydrolysis inherently, there do not appear to be many differences in gastric emptying time between Whey Isolate and Whey Hydrolysate, when consumed at 45g under fasted conditions in healthy males.^[73]

A general rule of thumb is that whey is emptied from the stomach faster than casein, although the addition of enzymes in milk makes the food product a grey area. Coingested nutrients may also influence gastric emptying rates

In one intervention where nitrogen content, energy density, osmolarity, liquid volume, and caloric content were all matched; there were no apparent differences in gastric emptying between whole whey and casein as well as their hydrolysates.^[74]

Whey protein appears to be less effective, relative to casein protein, at slowing intestinal motility rates.^[72]

Whey protein seems to spike in the blood approximately 40-60 minutes after ingestion, as assessed by measuring the leucine spikes in the blood.^[75] During this time an increased insulin release is also seen of which both the C_max and the AUC exceed that of an equal dose of casein protein.^[76][77] Whey tends to be spiked in the blood quicker than common food sources of protein such as tuna, turkey, and egg.^[78]

When measuring leucine kinetics after ingestion of 20g protein (seen as a biomarker for potential muscle protein synthesis), the peak levels (C_max) of leucine reach a positive net balance of 347+/-50nmol/min/100mL from whey protein while casein protein has a lesser peak value at 133 +/- 45nmol/min/100mL.^[76] When looking at long-term leucine balance in the body, casein protein appears to have greater retention than whey protein.^[75][79]

While whey protein appears to be more potent at stimulating protein synthesis (68% above baseline by whey, 31% by casein) whey protein fails to inhibit protein breakdown while casein can reduce protein oxidation by 31%.^[75] The net result is either similar accumulations in muscle tissue content after ingestion of equal amounts of whey or casein protein,^[76] or better retention with casein over 7 hours if nothing else is ingested;^[76] this is despite 30% greater leucine uptake into muscle cells when measured at 2 hours post ingestion relative to casein.^[76] One study that divided protein synthesis rates into a 60-210 minute period and a 210-360 minute period noted that whey increased protein synthesis significantly more than casein in the first period only, with the opposite result occurring in the latter period and no overall difference over the 5 hours tested, although casein trended towards being more effective.^[77]

Whey protein has been investigated for its ability to reduce blood pressure due to the presence of several ACE-inhibiting peptides derived from both alpha-lactalbumin and beta-lactoglobulin.^[80][81] These peptides appear to be effective in lowering blood pressure in spontaneously hypertensive rats^[82] and similar ones have been reported for casein protein.^[83][84]

One particular small peptide of Valine-Proline-Proline (Val-Pro-Pro) is derived from sour milk and sold in Japan under the brand name Ameal.^[85] Isoleucine-Proline-Proline (Il-Pro-Pro) also appears to be another bioactive peptide small enough to be absorbed in vivo through tripeptide transports.^[85] [86] Val-Pro-Pro has been shown to reduce the anti-hypertensive benefits of Green Tea Catechins somewhat.^[87]

Via digestive proteins (larger proteins being broken down into small peptide chains that happen to be bioactive) whey protein may be able to reduce blood pressure

In a long-term study on elderly women consuming whey protein (30g protein, 600mg calcium; control group had sugar), it was found that an estimated increase of 18-22g total dietary protein daily was unable to significantly benefit blood pressure over the course of 2 years; this study had persons using antihypertensive medications with unknown interactions with Whey protein.^[88] Another study on persons with hypertension consuming a whey drink with enhanced ACE inhibitory fragments for 12 weeks also reported no significant effects on blood pressure relative to control^[89] although a similar study protocol used previously has noted significant reductions in blood pressure over 21 weeks (-6.7mmHg systolic, -3.6mmHg diastolic; relative to control).^[90] while whey protein in general has been shown to reduce blood pressure in obese subjects relative to casein and glucose controls.^[91]

Some acute studies do note a decrease in blood pressure, but 45g whey isolate was not significantly different than 45g sodium caseinate (casein) or from 45g of glucose as a control^[92] (it should be noted that ingestion of almost anything, acutely, can reduce blood pressure slightly,^[93] whey just outperformed casein and glucose when calories were controlled). Changes in lipoproteins with this study design are also insignificantly different, although there was a significantly lesser release of triglycerides after the consumption of whey relative to both casein and glucose.^[94]

Studies on Whey protein being added to the diet to reduce blood pressure in hypertensive persons are mixed

Consumption of a meal with whey protein (relative to gluten, cod, or casein protein) appears to result in a lesser spike in CCL5,^[95] which is a recent biomarker for artherosclerosis where lower levels are seen as desirable.^[96] A lower spike in triglycerides are also seen in diabetic patients when comparing these four protein sources.^[97]

An intervention pairing whey protein with resistance exercise in obese males found that the addition of whey (relative to a resistance training and placebo group) found increases in HDL cholesterol and total antioxidant capacity (secondary to glutathione) while exercise per se was able to reduce LDL cholesterol.^[45] The combination was seen as most cardioprotective.

One intervention in rats using Whey protein hydrolysate noted that, relative to concentrate and isolate as well as Branched Chain Amino Acids, that hydrolysate was more effective in increasing glycogen when measured 2 hours after ingestion^[98] which was later credited to increasing the protein levels of Glycogen Synthase, which reached 153% of control after hydrolysate yet only 89.2% of control after mixed amino acids mimicking whey.^[99] 

This may be due to dipeptides in whey hydrolysate consisting of differing BCAAs being able to stimulate glucose uptake, with their efficacy at 1mM ranging from 1.61-1.88nmol/10 minutes, where insulin at 100nM concentration used as a positive control was 2.12nmol/m.^[100] These peptides can be absorbed from the gut via the Pept-1 transporter.^[101]

L-Cysteine, the amino acid present in whey's immunoglobulins, is seen per se as potential adjunct therapy for Diabetes type II.^[47] The theory is that increased dietary L-Cysteine content will improve glutathione stores in cells (demonstrated in unhealthy^[102] and healthy persons^[44]) and this can alleviate the risk for diabetes when the risk is caused by oxidative stress, which is a potential predisposing agent that can perturb insulin signalling.^{[103][104][105]}

In animal models, pairing L-Cysteine with a meal can acutely improve postprandial glucose tolerance^[106][107] and improve long-term glucose control when a part of the diet.^{[108][109][110]} This pairing also applies to the addition of Cysteine vicariously through whey or alpha-lactalbumin.^[106][107] Other effects that can be seen as beneficial to the state of Type II Diabetes have also been noted with Whey or Cysteine supplementation in these animal models, such as anti-inflammatory effects,^[111][110] protecting against endothelial dysfunction,^[112] a lowering of HbA1c and insulin resistance,^[110] cellular glucose toxicity,^[113][114] and in general most studies record a reduction in parameters of oxidative stress.^[110][105]

When looking at exclusively human studies, Whey Protein added to a meal (with no comparative protein source) appears to increase insulin secretion and reduce the post-prandial (after meal) exposure to glucose by 21%.^[115] Adding 4.4g of Branched Chain Amino Acids to 25g of a glucose drink can decrease the exposure to glucose (AUC) by up to 44% while adding 18g of whey can reduce it by 56%.^[31]

Whey appears to be somewhat effective as a diabetic adjunct treatment, being able to reduce post-prandial glucose levels and possibly confer benefits to pancreatic function secondary to L-Cysteine

In a study on diabetics, who tend to have elevated triglycerides after a meal (due to higher glucose) whey protein can reduce meal-induced spikes in triglycerides.^[97]

In general, whey protein is seen as beneficial to the lining of the intestines, especially in clinical settings where intestinal function is impaired.^[116] One study in rats found that whey, to a greater extent than soy or casein, could promote GLP-2 activtiy in the intestines and subsequent intestinal cell growth.^[117] Anabolism of gut tissue may only apply to higher quality proteins (those with complete amino acid profiles) as at least one study found an absence of anabolism after gelatin protein.^[118]

At least one human intervention has noted that whey protein at 0.5g/kg bodyweight for 2 months in persons with Crohn's Disease was approximately as effective as Glutamine at 0.5g/kg bodyweight in reducing intestinal permeability; this study actually used whey as an active control before concluding its efficacy.^[119]

A pilot study has been conducted on whey protein supplementation and its interactions with non-alcoholic fatty liver, and 20g whey protein for a period of 12 weeks in addition to a standard diet was able to reduce liver enzymes (ALT down from 64.89U/L to 45.89U/L; similar reductions in AST and GGT) and reduce liver fat deposits while improving glutathione (an endogenous anti-oxidant enzyme) status.^[102] These improvements were credited to the Cysteine fragment of Whey protein, which has been demonstrated previously in a sample of HIV positive persons to increase glutathione status.^[37] A significant reduction in body weight and waist circumference was also seen, but there was no control group to compare it to (pilot study).^[102] High doses of whey protein (60g daily) in obese women with high liver fat content was able to reduce fat build-up in the liver by 20.8+/-7.7% over 4 weeks and secondary to that reduce triglycerides and total cholesterol, with no influence on insulin sensitivity.^[120]

One study in humans with Hepatitis C noted that whey protein concentrate was able to reduce inflammatory markers and improve liver enzymes over a period of two months relative to control group.^[121]

These protective effects have been seen in rats alongside improved histological results and improved oxidative status^[122] which also confers an anti-oxidative buffer during exericse, known to induce oxidative damage.^[123]

Probably via the cysteine content of whey, Whey protein appears to be quite protective and rehabilitative of the liver and may improve some lipid parameters (triglycerides mostly)

Although not specific to whey, protein in general (and most commonly an excess of protein) has been said to cause renal (kidney) damage to healthy humans. This claim has been the subject of many reviews, and conclusions tend to cluster around 'no adverse effect of protein' with intakes up to 2.8g/kg (1.27g/lb) intake in athletes with higher levels not tested,^[124] obese persons with normal renal function having no apparent harm from a high protein diet for a year,^[125][126]. The one study to specifically isolate whey protein is confounded with Conjugated Linoleic Acid and Creatine (also usually said to harm kidneys yet hasn't been shown to) but found no abnormalities over 5 weeks with 36g whey protein in addition to a normal diet.^[127]

When protein is acutely increased in the diet, glomerular filtration rate (a biomarker of renal health) and renal blood flow can be increased (in the range of 10-15%) with no apparent harm to the kidney^[128][129] and seems to spike more after acute ingestion of animal proteins relative to plant protein.^[130] Over a longer period of time, glomerular filtration rate (GFR) appears to be higher (seen as better) and less renal vascular resistance with animal protein than with plant protein, with dairy protein (whey) as an intermediate;^[130][131] extending this logic shows that vegans and vegetarians have lower GFRs than do omnivores, although neither population inherently has better or worse renal function (merely reflective of dietary protein intake).^[132] In general, GFR is higher on high protein diets when compared to lower protein diets.^{[133][134][135][132]}

This apparent lack of harm is due to a highly variable excretion rate from the kidneys that correlates with dietary intake,^[134] and these physical adaptations do not inherently signal kidney damage.^[136]

In otherwise healthy individuals, and to specify, this section refers to those without kidney impairment, protein intake does not appear to adversely affect kidney function. There is an apparent increase in glomerular filtration rate (GFR) with higher protein diets and acute protein ingestion, with an inverse decrease in GFR with low protein diets; these fluctuations of GFR are not associated with kidney abnormalities if the kidneys were healthy to begin with; but signify adaptation to new dietary intake

Although there are "no clear renal-related contraindications to HP diets in individuals with healthy kidney function",^[137] protein intakes and whey protein may be contraindicted in persons with kidney impairments. The most commonly cited is acceleration of chronic kidney disease, where an inherent reduction of glomerular filtration rate seen during disease pathology (indicative of the failing potential of the kidney) appears to be accelerated when dietary protein is raised.^[138][139]

In persons with impaired kidney function, additional protein can exacerbate the decline in kidney function. These populations may be already placed on a low protein diet by a Medical Doctor, and should speak to a physician before using Whey Protein

A component of whey protein known as Alpha-Lactalbumin has been investigated for its neurological roles due to its high tryptophan content^[140] and apparent bioactivity in improving mood secondary to the tryptophan content;^[140] in rats has shown protective effects and better seizure control as assessed by myoclonus (involuntary muscle twitch) onset rates.^[141]

One pilot study in epilepsy noted that the addition of alpha-lactalbumin to whey (as a vessel for tryptophan) was able to improve seizure control in persons with drug-resistant epilepsy.^[142] A proof-of-concept study using alpha-lactalbumin supplementation from whey had 13 persons experiencing myoclonus twitches due to medical conditions taking isolated alpha-lactalbumin at doses of 1.5g daily, working up to 4.5g daily by the third week. This study reported that there was no significant effect on myoclonus movements while anti-depressive effects and improved sleep quality were seen, with half the patients opting to remain on treatment after the study concluded.^[143]

The two main whey proteins, a-lactalbumin and β-lactoglobulin, appear to enhance innate immunity by enhancing neutrophil function.^[144]

Macrophages have been found to have enhanced function via a tripeptide of Glycine-Leucine-Phenylalanine derived from a-lactalbumin^[145] as well as by low concentrations of glycomacropeptide (GMP), another component of whey.^[146]

An enhanced production of spleen^[147] and lamina propia^[148] lymphocytes has been noted with β-lactoglobulin

Lactoperodixase as well as Lactoferrin appear to have suppressive actions on lymphocyte proliferation, but these effects are not observed in a whey protein concentrate mixture.^[149]

Glycomacropeptide has been shown to influence immunity in the intestines, exerting anti-inflammatory effects in a rat model of colitis.^[150]

Whey protein, relative to cod and gluten protein in obese subjects, appears to cause less of a suppression of MCP-1 (a cytokine needed for immune cell infiltration of tissues) after a meal that is inherently anti-inflammatory; suggesting it may be less anti-inflammatory than cod or gluten protein.^[95] Dairy in general appears to be better at suppressing MCP-1 than does soy protein according to a 28-day crossover trial in obese adults,^[151] and this general anti-inflammatory trend of dairy (as assessed by cytokines) appears to extend to lean individuals as well, although this latter study was not a controlled intervention.^[152]

Many of Whey protein's effects with cancer are due to the Cysteine rich fragments enhancing Glutathione production.^[36]

Interestingly, a study conducted in tumor cells that expressed high levels of glutathione (hindering the efficacy of chemotherapy) found that 30g of whey protein for 6 months as a Cysteine-delivery system in 5 persons with metastatic cancers (7 persons total) seemed to reduce tumor size in 2 persons (28%), stabilize tumor size in two persons, and had no effect on the other three.^[153]

Lactoferrin is a bioactive peptide with an ability to bind iron, and it has been shown to be anti-cancer which may not be related to its iron binding properties; that being said, when it becomes saturated with iron molecules it can become a potent anti-cancer protein^[154] and can modulate oxidation.^[155] In vitro studies suggest certain peptides as well, usually lactoferrin, may induce cell death in tumor cells and exert cancer-protective mechanisms in melanoma cells,^[156][157] breast cancer cells,^[25] stomach cancer cells,^[158] lung cancer cells,^[159] lymphoma cells,^[160] and colorectal cancer cells and polyps.^[161] This last cell line has been shown to be effective in humans with isolated bovine lactoferrin at 3g daily,^[161] establishing its role as a colonic anti-tumor agent.^[162] Translating the 3g bovine lactoferrin used in the aforementioned colon cancer study and assuming a 0.5-1.6% lactoferrin content of whey, this corresponds to 187.5-600g whey protein (rather high).

Lactoferrin appears to be endogenously produced in humans and is an aspect of the immune system, while lactoferrin in when (bovine lactoferrin) can mimic its actions somewhat.^[163]

Although a promising whey-derived anti-cancer molecule, the content of lactoferrin in whey may be too low to exert appreciable effects

Whey protein has been associated with improvements of cancer-related cachexia in at least one case study,^[164] although this case used testosterone enanthate at low doses and highly confounds the results. The usage of whey in this case was for a surplus of amino acids, and the benefit may not be isolated to whey protein per se.^[164] At least one blinded trial using leucine-enriched whey and casein proteins increased protein synthesis rate in cancer patients and suggested modifying hospital foods may aid in cancer cachexia.^[165]

Whey and casein hydrolysates seem to induce greater gastric acid secretions relative to whole proteins, and induce more secretion of glucose-dependent insulinotropic polipeptide.^[74]

One study comparing whey protein against a non-caloric placebo found that whey protein, in middle-aged and older men, was associated with an increase in Myostatin binding protein FLRG but that a decrease in Myostatin itself was observed only in placebo; suggesting that protein intake and exercise influences myostatin function.^[166] A later study in otherwise healthy men also noted that the exercise-induced suppression of Myostatin occurred only in placebo with whey apparently suppressing this action^[167] and has been replicated elsewhere.^[168]

At least in rats, the increase of Myostatin associated with immobility is not suppressed by protein supplementation either.^[169]

Counter-intuitively, may prevent the suppression of Myostatin induced by exercise relative to control groups; this seems to apply to protein in general

Pairing protein ingestion and exercise stimulates muscle protein synthesis to a greater extent than does ingestion of protein alone over the course of 6 hours (measured), suggesting time-dependent pairing.^[170] One study comparing resting protein synthesis rates against protein synthesis rates after exercise (same participants and protein content) noted a variable increase of 30-100% higher protein uptake into muscle tissue when exercise preceded, with protein synthesis being 291+/-42% higher than baseline when amino acids and exercise were paired and 141+/-45% after amino acids only^[171] (although when comparing isolated amino acids, only the essentials seem to be needed)^[172]. At least one study noted that this increased sensitivity of muscle tissue to amino acids can last up to 24 hours,^[173] so once daily exercise can theoretically suffice. In older individuals, some damage to the muscle cell (via resistance training) may be needed to achieve protein synthesis rates similar to youth, and even then at a slightly higher intake of 40g^[174] to a youth's 20g.^[175]

Many other studies note significantly more muscle protein synthesis relative to control, with higher levels of Myofibrillar FSR relative to nothing,^[77][76] higher acute levels of amino acid uptake into muscle paired with amino acid retention,^[5] a higher net nitrogen retention relative to a non-intervened group (independent of timing),^[176] 

Protein is better than nothing when it comes to Muscle Protein Synthesis acutely, and Protein's benefits are augmented with resistance exercise. The importance of the combination may be further elevated in the aging person

A study conducted on resistance-trained males already following a 4-day weekly split intervened with both whey paired with casein (40g, 8g) and whey paired with additional BCAAs and Glutamine (40g, 5g, 3g) against placebo (40g carbohydrate) and found that, over the course of 10 weeks and with an overall dietary intake of 2.1g/kg protein in the two protein groups, that whey plus casein was able to enhance lean mass gains over 5 weeks with no further effect over 10 weeks relative to placebo.^[177] The results of this study may have been influenced by less initial body weight in this group, which seemed to normalize.^[177] In young untrained men, whey protein is significantly more effective than carbohydrate at inducing muscle protein synthesis and accumulating lean mass over a period of 14 weeks, when the average protein intake prior to intervention was 97+/-5.3g (1.2g/kg); muscle growth seen as 18% and 26% for type I and type II fibers.^[178] Consumption of fat-free milk (17.5g protein, 25.7g carbohydrate) has also been shown to increase lean mass over a period of 12 weeks, and did so to a greater degree than soy protein when all subjects consumed 1.2-1.4g/kg protein before intervention^[179] and in addition to an ad libitum (no dietary controls) diet.^[168]

Many studies do note that the addition of protein does not confer additional benefits, however, in both youth^[180] and older subjects^[181][182] localizing protein intake around workouts. One study increasing protein intake from 1.4-1.8g/kg up to 2.16-2.28g/kg in highly trained athletes^[176] found that the addition of 40g whey protein to elevate overall protein intake, regardless of timing, failed to induce changes in lean mass or fat mass over 12 weeks.

Another study that found no effects of whey protein used 10, 20, or 30g taken twice daily in overweight and obese persons for 9 months, and in conjunction with a thrice-weekly workout regimen (2 weight training sessions, 1 aerobic) found no improvements on any metabolic parameter including body composition.^[183] This study also experienced a 42% dropout rate over the study period, and although benefits were seen to lean mass and fat mass they were attributed to weight training due to not significantly differing between the three test groups.^[183]

The addition of protein to a diet does not inherently increase Muscle Protein Synthesis, studies that have the subjects consuming higher protein levels (as part of their normal diets) tend to show less promising results than those who underconsume protein (which tend to be studies done in the elderly, confounding the research for athletes quite a bit)

Two studies have been conducted assessing at what point protein synthesis is maximized after resistance training when ingesting protein, one in youth^[175] and one in older individuals.^[174] In younger adults (n=6) with previous resistance training experience being tested with 5, 10, 20, and 40g egg proteins it was found that dose-response existed up until 20g protein for 4 hours post exercise, with no added benefit with 40g despite increasing circulating amino acids higher than 20g; this study was conducted with a diet of 1.4g/kg bodyweight and exercise was conducted in a fasted state.^[175] When tested in older men (n=37) 20g of protein was again found to increase muscle protein synthesis, but when paired with resistance training exercise 40g appeared to be more effective in increasing muscle protein synthesis (95% more than baseline, relative to a 60% increase seen with 20g;^[174] the youth experienced a 93% increase with 20g^[175]). Interestingly, elderly persons are also more responsive to fast protein sources and acute spikes in amino acids relative to younger persons.^[184]

Maximal protein synthesis rates seem to be met at lower circulating amino acid levels in youth relative to elderly persons. Due to the protein synthesis rates being similar at 20g in youth and 40g in elderly persons, it suggests inefficiency of amino acid utilization in elderly persons. Not too much data on graded intakes, however

One study conducted in older persons (n=24) found that there was no significant difference in protein synthesis rates when comparing casein protein 30 minutes before or after exercise (2 different groups) and whey after a workout when measured for 6.5 hours after exercise, although all three groups outperformed placebo.^[185] This study used 15.6-30.4g protein (0.45g/kg lean body mass) and did note a higher C_max of plasma leucine, insulin, and AA concentration with whey after about 2-3 hours.^[185]

When comparing protein sources against each other, in regards to consuming them near the workout, there may not be any significant difference between protein sources if looking at the entire day or a longer period of time. Whey protein may have higher protein synthesis rates if measured for the subsequent 2-3 hours after ingestion, however; other protein sources catch up

One of the more well-conducted studies on the matter (10 weeks in duration, resistance trained young men, moderate to high level workout protocol) found that 42g whey protein (3.6g leucine) given to 33 men either as a morning and night shake (2 shakes, group A) or a pre and post workout shake (2 shakes, group B) ^[176] found that both groups supplemented protein (and bringing total protein intake up to 31.5-31.6% from 20.8-23%; or 1.4-1.8g/kg up to 2.16-2.28g/kg) had an increase in bench press strength with no difference between protein groups, and no difference between the two protein groups and control in regards to squat strength increases or body composition.^[176] The authors hypothesized that the lack of results were due to a plateau in protein-induced benefit at around 1.6g/kg in athletes. Similar results have been seen in a 16-week trial on diet induced weight loss in type II diabetics already placed on a high protein (33% of 6000-7000kJ, 1.2g/kg for obese persons) diet, where timing of a high protein snack (21g skim milk protein) prior to exercise relative to another time of day had no effect on body composition, energy expenditure, or all measured glycemic or lipid profiles (which all improved with weight loss).^[186]

Contrary to this, a 12-week resistance training program in previously sedentary elderly men (with a dietary intake of 1g/kg bodyweight protein before intervention) showed benefits on lean mass accrual when the protein supplement was consumed immediately after training (1.8 ± 0.7%) relative to 2 hours alter (1.5 ± 0.7%) as well as thigh circumference, with 1 rep max strength (but not 5 rep max) strength also improving.^[187] This study, however, used a skim milk/soybean blend at 10g protein (7g carb, 3.3g fats) and was the only source of nutrition for the 2 hours after exercise.^[187] Another study on sedentary older individuals (55-75) found that despite the same amount of protein ingestion per day over 3 days, timing 15.3g protein (milk protein, 4g of whey) after exercise (relative to carbohydrate) paired with a slightly caloric increase in both groups led to a 57% greater protein accumulation in the group that consumed protein after exercise.^[188] This study used a lead-in diet of 15% protein (30% fat, 55% carbs), and is a low overall intake.

The benefit of whey protein being timed around workouts may be dependent on low dietary intake of protein, with more efficient protein utilization occurring near a workout; these benefits may be 'washed away' by overconsuming protein, making the importance of timing inversely related to overall dietary protein intake. The notion that nutrient timing may be relevant to older individuals is also possible

One study on 6 healthy and untrained volunteers, an essential amino acid (EAA) solution of 6g taken alongside 35g carbohydrate in a fasted state was significantly more effective in improving muscle protein synthesis (as measured by phenylalanine incorporation) when taken immediately before when compared to immediately after.^[189] This study did not note any differences in workload, blood flow, or amino acid levels in the blood aside from timing.^[189] Another study using the same formulation, sample size, and in a fasted state but comparing 1 hour after against 3 hours after noted that no significant differences existed in insulin secretion, glucose uptake, or overall protein synthesis or breakdown up to 4 hours after intervention^[190] while another comparing immediately after and 3 hours after (exercise in a fasted state) using 10g protein, 8g carbohydrate, 3g fats found a 12% increase in muscle protein synthesis above baseline values in the 3-hour group yet a three-fold increase in the group consuming the drink immediately after cycling exercise.^[191]

Pre-loading some protein, if in a fasted state, may be better than consuming it after a workout with little to no pertinent need to consume the protein immediately after the workout. The 'one hour metabolic window' may apply only to fasted training where there is no pre-load, as some evidence suggests that sooner is better in this particular scenario only

Whey protein, and protein in general, may enhance recovery rates from exercise. In studies that induce muscular damage with weight training and subject participants to a form of protein or nothing, studies that ingest protein tend to recovery strength faster at subsequent workouts.^{[181][192][193]} When measured 6 hours after the first bout, the hydrolysate form of protein appears to be effective while Whey Isolate is not (previous studies done on subsequent days).^[63] The addition of amino acids or protein to an intentionally high volume workout plan can increase the amount of workload done over time.^[194]

In studies that measure delayed onset muscle soreness (DOMS), no significant effects are seen between carbohydrate,^[193] milk, or a combination of the two^[181] no significant differences between water, whey isolate, and whey hydrolysate when measured 6 hours later,^[63] The studies that do note less DOMS are those that have protein consumed 30 minutes before exercise, suggesting pre-loading may be of importance;^[195] this has also been noted with isolated Branched Chain Amino Acids, where taking BCAAs before exercise reduced DOMS.^[196]

Preloading protein, possibly via the BCAAs or Leucine, can reduce soreness induced from exercise; this effect is not seen when taking protein after a workout. Protein appears to enhance the rate of power recovery following exhaustive exercise, but no evidence exists to say that this applies to only whey protein (may work through protein inherently)

Supplementing with Whey protein during exercise does not significantly suppress fat oxidation during exercise despite the insulin release from select amino acids.^[197]

When investigating Whey protein against other common protein sources (skim milk, casein protein) no differences in energy expenditure post-consumption are noted.^[198]

However, one study (n=8) comparing protein (18g whey, 2g carbohydrate, 1.5g fats) against carbohydrate (19g carbs, 1g whey, 1g fat) when both are ingested before weight training found that both groups experienced an increase in metabolic rate due to weight training, but the increase was preserved in the protein group when measured at 24 hours.^[199] There was no significant difference in workload performed during the workouts or in the diets (proteins or calories), and although the difference in metabolic rate was measured at 5.1kJ/kg/d (a 5% increase) this difference disappeared by 48 hours; this study was not designed to compare pre and post workout protein timing.^[199]

Protein doesn't appear to inherently increase metabolic rate (as assessed by oxygen consumption) beyond the thermic effect of food, but may have some synergistic interactions with exercise

After consumption of 55g whey protein (in two doses of 27.5g with meals) it was found that T3 uptake was lower relative to soy protein (30.9+/-0.5 versus 32.5+/-0.4) and free T4 was lower in whey (13.7+/-0.1pmol/L) than in soy (14.5+/-0.3pmol/L), although this study noted weight loss with the Whey group (2.8kg over 23 weeks).^[200] Thyroid hormones tend to increase more in general when dietary protein increases (relative to carbohydrate^[200][201]) and it appears Whey is slightly less effective than Soy at this.

Due to whey protein's satiety value (ability to induce the sensation of fullness), it can reduce body fat over time through reduced overall food consumption.^[202] Glycomacropeptide and CCK influence this a bit, but it seems to have subtle influences rather than potent appetite suppression.^[203][204]

There is mixed human data on whether a pre-load of whey protein suppresses appetite in subsequent meals, one study found 20g whey administered 30min before food did not have an effect while casein and pea did^[205] whereas another study found the opposite effects with the same dose and timing (although it noted that hydroslates rather than concentrates did not have this suppression of appetite).^[206] Increasing the time between the pre-load and meal seems to reduce any potential appetite suppression^[207] and in this regard there appears to be a 'more-is-better' relationship^[206][208] as 50g of whey protein has shown appetite suppressing effects 4 hours after consumption in lean men.^[78]

Some studies report less food intake, yet no changes in subjective parameters of appetite.^[198] This particular study had whey showing benefit, but was outperformed by Skim Milk.^[198]

One intervention of 138 subjects given either 10g whey protein or 10g glucose over 12 weeks found that a 500kcal deficit was able to induce weight loss in both groups, but those consuming whey had 6.1% body fat loss compared to 5% in the glucose control; this study used an American Heart Association style diet (15% protein and 55% carbohydrates) and had funding from the company providing the protein.^[209]

One study comparing 52g whey protein isolate against soy and carbohydrate (2 different groups) found that, despite keeping calories static, whey protein outperformed soy protein and glucose control at reducing fat mass when combined with a caloric deficit (0.9kg more than soy and 1.8kg more than glucose over 23 weeks).^[200] The protein groups averaged 1.4g/kg bodyweight while the glucose control had 0.8g/kg protein consumption, and this study may be influenced by a reduction in carbohydrates seen in the whey protein group that reached significance.^[200]

Conversely, studies that do not find reductions in body weight exist. One intervention used whey against glucose and casein control groups in overweight/obese persons for 12 weeks and found improvements in cardiovascular health biomarkers (blood pressure) yet no significant weight loss.^[91]

Whey protein does not seem to induce fat loss when the diet is not controlled, and may not influence fat loss when substituted in the diet. For intentional weight loss purposes that have a low dietary intake of protein, whey protein supplementation appears to enhance fat loss and preserve lean mass (these effects are most likely due to protein inherently, and not whey protein specifically)

When compared to casein protein, whey shows higher levels of serum BCAAs and muscle protein synthesis at the same dose for the 1-6 hours following exercise^[77] and drastically elevated levels of muscle protein synthesis at both rest and post exercise when measured within an hour.^[215] This is hypothesized to be due to a combination of digestion speed and leucine levels, which appear to spike much more rapidly than casein protein despite no differences in overall exposure (as assessed by AUC).^[216][217] Despite this increased C_max of amino acids and higher peak of protein synthesis, studies are highly mixed when comparing whey against casein. Whey appears to effectively increase protein synthesis more in older individuals compared to casein,^[185][184] while in youth casein seems to cause slightly more overall nitrogen retention on the body.^[217] At least one study notes the most benefit with a combination, although this study used 40g whey to 8g casein (somewhat reverse of the ratio found in Milk).^[177]

In a study on COPD (Chronic Obstructive Pulmonary Disease), characterized by disturbed amino acid metabolism, casein appears better than whey at inducing protein retention and possibly building muscle mass (study was too short to conclude the latter statement).^[218]

To make a general statement on the comparison, it seems that most benefits associated with either Whey or Casein are due to them inherently being protein. Whey might benefit the elderly more than Casein, and vice-versa for youth. The degree that one is better than the other (in regards to protein synthesis) is minimal relative to the degree they are both better than a protein deficient diet

Against casein (as sodium caseinate) Whey protein seems better able to reduce spikes in Triglycerides seen after meals with fatty acids in them^[94] and can reduce triglycerides over a period of 6 weeks; outperforming casein but not reaching statistical significance in doing so.^[219] When paired against casein, whey protein seems to be better at reducing LDL cholesterol and Total cholesterol over a period of 6 weeks, and appears to more favorably influence insulin sensitivity and insulin AUC compared to casein.^[219] One study in rats failed to replicate the reduction in triglycerides with 100% of the diet as whey relative to a group with all casein, but demonstrated an increase in HDL-C over casein.^[220]

One study in rats found a significantly higher fasting glucose level relative to both casein and a 30/70 whey/casein blend, when they were the exclusive protein sources in the diet.^[220]

When measuring anti-oxidative abilities (in a clinical setting), whey protein confered greater anti-oxidative and anti-inflammatory effects as assessed by glutathione and IL-6; respectively.^[221]

Whey appears to be better able to normalize select blood biochemistry, and could potentially be called 'healthier' than casein protein; these may be vicarious through the L-Cysteine component

Soy protein (not to be confused with Soy Isoflavones) failed to change body composition in one study, when Whey protein was able to in obese adults.^[200] This study compared Whey against Soy (active control) and carbohydrate (control) and also controlled for caloric intake in 73 overweight or obese (but otherwise healthy) adults. Control subjects (glucose) gained gain weight and the subjects who took whey protein lost 1.8kg over 23 weeks despite an increase in total calories. Soy protein supplementation increased total dietary protein to similar levels as the whey protein, but did not cause a change in bodyweight. The whey had 1g more leucine and 1g less glutamine than soy and at the end of the trial the whey group had 2.3kg less body fat mass compared to glucose only despite consuming (insignificantly) more calories daily.^[200] These results have also been repeated in youth subjected to weight training, where in addition to a diet of 1.2-1.4g/kg bodyweight protein, the addition of 17.5g skim milk was able to add lean mass while reducing fat mass over 14 weeks and soy was ineffective at doing so.^[179] However, at least one study has noted that assigning larger amounts of protein (1.2g/kg) can make the differences between whey and soy insignificant, with both outperforming placebo.^[222]

After consumption of 55g whey protein (in two doses of 27.5g with meals) it was found that T3 uptake was lower relative to soy protein (30.9+/-0.5 versus 32.5+/-0.4) and free T4 was lower in whey (13.7+/-0.1pmol/L) than in soy (14.5+/-0.3pmol/L), despite the Whey group losing more fat.^[200] Thyroid hormones tend to increase more in general when dietary protein increases (relative to carbohydrate^[200][201]) and it appears Whey is slightly less effective than Soy at this.

In a crossover intervention in older women (n=9) comparing hydrolyzed collagen protein against whey isolate with the diet controlled to 0.4g/kg bodyweight (low amounts said to sensitize to changes in protein supplementation by the authors) and having the supplements bring the totals up to 0.8g/kg, it was found that hydrolyzed collagen was better able to preserve body weight with no significant differences in nitrogen balance.^[223] Over 15 days, weight decreased by 0.81±0.28kg in whey and 0.50±0.27kg in collagen, with no differences in percent of fat or lean mass lost.^[223]

Not much evidence to compare these two protein sources, and the one study is fairly low powered

A study comparing whey protein against carbohydrate as well as their combination found that relative to 1.6g/kg carbohydrate, 1.2g/kg carbohydrate paired with 0.4g/kg protein after cycling (same amount of calories) was better able to enhance muscle protein synthesis but did not significantly influence glycogen replenishment rates.^[224]

Another study investigating co-ingestion of whey and carbohydrate on protein synthesis found that, in 10 trained young cyclists exercising at 77% of their VO2 max for 90 minutes, the addition of 10g whey protein to 35g carbohydrate enhanced myofibrillar protein synthesis by 35% relative to carbohydrate alone with no apparent benefit above carbohydrate for mitochondrial protein synthesis.^[225] This enhancement was observed alongside increased phosphorylation of mTOR, p70S6K, and eEF2.^[225]

Leucine is the main amino acid found in Branched Chain Amino Acids, known as BCAAs.

At least one study has investigated whether the addition of leucine to a protein and carbohydrate drink (used as an active control) provided any more benefit to young (22.3+/-0.9yrs) untrained males subject to physical training, and it was found that the addition of 0.1g/kg leucine to the drink (0.2g/kg whey hydrolysate at 9.95% leucine already, 0.3g/kg glucose and maltodextrin) was able to further lower protein oxidation rates relative to just the protein and carbohydrates.^[226] A greater insulin response (AUC_0-6) was also seen after the addition of leucine, almost two-fold higher than the protein and carbohydrate combination,^[226] and protein synthesis rates were slightly higher with the addition of leucine.^[226] This study design was replicated in elderly (73+/-1yrs) men and it was found that the addition of leucine to protein and carbohydrate further decreased protein oxidation rates and increased the amino acid pool, but this study failed to show further improvements in muscle protein synthesis.^[227]

The influence of protein and leucine combinations does not appear to differ to significantly with age, although this study^[228] noted an increase in muscle protein synthesis rates while the aforementioned study^[227] failed to see these effects.

When comparing 3g of leucine against 25g of whey protein of which contains 3g leucine, it was found that leucine seems to be causative of most phosphorylation of p70s6k and mTOR (proteins that are activated to induce muscle protein synthesis) and rivaled whey's initial increase in muscle protein synthesis, but failed to further increase muscle protein synthesis in the 3-5 hour time period while whey further increased MPS.^[229]

The addition of leucine (0.1g/kg) to whey protein (0.2g/kg) might further enhance the benefits of whey protein; whether increasing the protein content to get more leucine (vicariously through whey) confers the same benefit is unknown

Zinc is an essential mineral involved in bone, hormone, and enzyme metabolism. The addition of 30mg zinc to a whey drink in the frail (hospitalized) elderly is able to enhance IGF-1 secretion from 22.4+/-4.7% to 48.2+/-14.3% (average 215% more secretion) and further better activities of daily living.^[230] Whey, as well as casein, are able to increase IGF-1 secretion and may be of benefit to older individuals in reducing frailty.^[231][232]

Protein digestive enzymes are sometimes paired with protein to 'enhance absorption'. One open labelled study has been conducted on the matter (funded by Triarco, supplier of patented enzymes used; conducted independently) found that pairing 2.5g or 5g of a proteolytic enzyme blend (Aminogen) with 50g whey protein concentrate found that the addition of enzymes increased the area-under-curve (AUC) of amino acids in the blood 2.2-fold with 2.5g Aminogen and 3.5-fold with 5g Aminogen.^[233] Serum amino acids were measured for 4 hours after ingestion, and 24-hour nitrogen excretion assessed by urine was lower in the Aminogen group.^[233]

Aminogen is a blend of enzymes from Aspergillus niger and Aspergillus oryzae, these results may apply to other compounds with protein digestive abilities such as Bromelain.

May accelerate the rate of absorption for whey concentrate, but more studies would need to be conducted for conclusions. The cessation of measuring at 4 hours after a 50g bolus of protein may favor the faster absorbing protein, when it is theoretically possible that there would be no significant AUC difference if measured at 8 hours

HAMLET is an acronym for Human a-lactalbumin made lethal to tumour cells, and is the quaternary protein a-lactalbumin from whey bound with oleic acid (found in olive oil as well as eggs).^[234] The binding of oleic acid to a-lactalbumin partially unfolds the protein, which is causative of the increased anti-cancer potential (via killing tumors) as native a-lactalbumin does not inherently attack tumors.^[234] It was first discovered in 1995^[235] and intentionally created in 2000 through an ion-exchange procedure in a medium with oleic acid^[236] and now has additional preparation methods.^[237] Beyond cancer cells, HAMLET appears to have potency in killing the bacteria Streptococcus pneumoniae.^{[238][236][239]}

HAMLET is the most well researched, but Oleic Acid has been shown to form complexes with bovine β-lactalbumin (component of Whey Protein)^[240] where binding of oleic acid induced thermal stabilization of β-lactalbumin and was as effective as HAMLET in inducing cell death in HEp-2 cells.^[240] Additionally, a-lactalbumin that is derived from cows milk (Bovine a-lactalbumin) is referred to as BAMLET.^[241] BAMLET and other variants of HAMLET such as the aforementioned complex of oleic acid and β-lactalbumin have comparable cytotoxicity to cancer cells.^[242][243]

One study investigating the effects of heat treatment noted that unfolding of the protein (denaturation) caused an enhanced subsequent production of BAMLET in vitro, but eventually the heat could cumulatively degrade the a-lactalbumin precursor and hinder BAMLET production.^[241] These results contrast earlier hypothesis' that changes to protein confirmation could abolish the effects of HAMLET/BAMLET.^[244] One the complex itself is formed, it has either equal to or lesser stability than the protein it was formed from; with one study noting that HAMLET was denatured at 15°C less than a-lactalbumin.^[245]

A promising anti-cancer complex of whey protein and olive oil components; no in vivo studies currently exist so beyond noting its potential no conclusions can be made as to efficacy or whether it can be digested or formed in vivo after consumption of the components

Whey is already a component of human breast milk,^[246][247] as are many of its bioactive peptides such as alpha-lactalbumin, which is seen as good for infant nutrition.^[17] Beyond that, whey is commonly added to infant formulaes due to its benefits associated with infant health (although usually in a hydrolyzed form, which might reduces the allergic potential yet has not been shown to have benefits over breast milk^[248]).

No human evidence exists directly assessing whether or not whey consumption per se is good or bad for infant health when consumed by a mother during pregnancy or lactation; one study in mice found that general overconsumption of protein (40% of the diet by calories) during pregnancy could slightly reduce birth weight of the pups, and during lactation it reduced the mRNA of bioactive proteins in the breast.^[249]

No compelling evidence to discourage usage in pregnancy, and whey as a naturally component of cheese and milk (consumed routinely during pregnancy) suggests moderate usage of whey protein is fine. Mothers should be aware of possible contaminants in poor brands of whey protein which has been reported in the media previously, although is seen as uncommon