Whey protein



Whey protein is a mixture of globular proteins isolated from whey, the liquid material created as a by-product of cheese production. Some preclinical studies in rodents have suggested that whey protein may possess anti-inflammatory or anti-cancer properties; however, human data is lacking. The effects of whey protein on human health are of great interest and are currently being investigated as a way of reducing disease risk, as well as a possible supplementary treatment for several diseases.

Whey protein is commonly marketed and ingested as a dietary supplement, and various health claims have been attributed to it in the alternative medicine community. Although whey proteins are responsible for some milk allergies, the major allergens in milk are the caseins.

Production
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. It is removed after cheese is processed. The fat is removed and then is processed for human foods. Processing can be done by simple drying, or the protein content can be increased by removing lipids and other non-protein materials. For example, spray drying after membrane filtration separates the proteins from whey.

Whey 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. Heat-denatured whey can still cause allergies in some people.

Composition
Whey protein is the collection of globular proteins isolated from whey, a by-product of cheese manufactured from cow's milk. The protein in cow's milk is 20% whey protein and 80% casein protein, whereas the protein in human milk is 60% whey and 40% casein. 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.

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 &mdash; they are 90%+ protein by weight. Both of these types are mild to slightly milky in taste.
 * Hydrolysates are whey proteins that are predigested and partially hydrolyzed for the purpose of easier metabolizing, but their cost is generally higher. Highly-hydrolysed whey may be less allergenic than other forms of whey. They are very bitter in taste.

Benefits for muscle building
Research indicates that the use of supplementary whey or soy protein combined with resistance training offers some benefit over no protein supplementation. However, the timing of protein supplement ingestion has no effect on strength, power, or body-composition.

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. Whey is an abundant source of branched-chain amino acids (BCAAs), which are used to fuel working muscles and stimulate protein synthesis. In particular, leucine plays a key role in initiating the transcription pathway that fires up protein synthesis. 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).

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. However, another study suggested that large amounts of whey protein can increase cellular glutathione levels. 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.