Whey protein

[sarasoso]

Main article: Whey
Whey is left over when milk coagulates* and contains everything that is soluble from milk. It is a 5% solution of lactose in water* with some minerals and lactalbumin.[7] It is removed after cheese is processed. The fat is removed and then is processed for human foods.[7] Processing can be by simple drying* or the protein content can be increased by removing lipids and other non-protein materials.[8] For example* spray drying after membrane filtration separates the proteins from whey.[9]
Whey protein can be denatured by heat. High heat (such as the sustained high temperatures above 72 °C associated with the pasteurization process) denatures whey proteins. While native whey protein does not aggregate upon renneting or acidification of milk* denaturing the whey protein triggers hydrophobic interactions with other proteins* and the formation of a protein gel.[8] Heat-denatured whey can still cause allergies in some people.[10]


Composition

Whey protein is the collection of globular proteins isolated from whey* a by-product of cheese manufactured from cow's milk. Cow's milk is 20% whey protein and 80% casein protein*[11] whereas human milk is 60% whey and 40% casein.[12] Whey protein is typically a mixture of beta-lactoglobulin (~65%)* alpha-lactalbumin (~25%)* and serum albumin (~8%)* which are soluble in their native forms* independent of pH. The protein fraction in whey (approximately 10% of the total dry solids within whey) comprises four major protein fractions and six minor protein fractions. The major protein fractions in whey are beta-lactoglobulin* alpha-lactalbumin* bovine serum albumin and immunoglobulins.[13]

Major forms

Whey protein typically comes in three major forms: concentrate* isolate* and hydrolysate.
Concentrates contain a low level of fat and cholesterol but* in general* have higher levels of bioactive compounds* and carbohydrates in the form of lactose — they are 29%–89% protein by weight.
Isolates are processed to remove the fat* and lactose* but are usually lower in bioactivated compounds as well — they are 90%+ protein by weight. Both of these types are mild to slightly milky in taste.
Hydrolysates are predigested* partially hydrolyzed whey proteins that* as a consequence* are more easily absorbed* but their cost is generally higher.[8] Highly-hydrolysed whey may be less allergenic than other forms of whey.[10] They are very bitter in taste.

Function

Whey is essential in the bodybuilding world today because of its ability to be digested very rapidly.[14] This allows the protein to become available for muscle building very quickly. Most commonly it is used after workouts to help increase levels of amino acids in the blood* which are taken up by the muscles to ultimately increase mass. In addition* during exercise* whey helps open up blood flow by inhibiting an angiotensin-converting enzyme which originally constricts blood vessels; this allows better flow of nutrients to necessary areas to help repair and rebuild muscle tissues.[15]

Health effects

The use of whey protein as a source of amino acids and its effect on reducing the risks of diseases such as heart disease and cancer is the focus of ongoing research.[3] Whey is an abundant source of branched-chain amino acids (BCAAs)[16] which are used to fuel working muscles and stimulate protein synthesis.[17] In particular* leucine plays a key role in initiating the transcription pathway that fires up protein synthesis.[18] When leucine is ingested in high amounts* such as with whey protein supplementation* there is greater stimulation of protein synthesis* which may speed recovery and adaptation to stress (exercise).[19]
Whey protein contains the amino acid cysteine which can be used to make glutathione. However* this amino acid is not essential for the synthesis of glutathione and some studies have suggested that the amount of cysteine in the diet may have little effect on glutathione synthesis.[20] However* another study suggested that large amounts of whey protein can increase cellular glutathione levels.[21] Glutathione is an antioxidant that defends the body against free radical damage and some toxins* and studies in animals have suggested that milk proteins might reduce the risk of cancer.[22]
Consumer Reports testing found that due to contamination* some bodybuilding protein shakes purchased online* and in the New York metro area* exceeded USP standards for exposure to heavy metals when three servings a day were consumed. Depending on each product’s individual serving-size recommendations* some three-serving samples involved as much as 210 grams (7.4 oz) of powder being tested. [23]