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.
Whey is left over when milk is coagulated during the process of cheese production, and contains everything that is soluble from milk after the pH is dropped to 4.6 during the coagulation process. It is a 5% solution of lactose in water, with some minerals and lactalbumin. The fat is removed and then 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.
Whey protein is the collection of globular proteins isolated from whey. 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. The protein fraction in whey constitutes approximately 10% of the total dry solids in whey. This protein is typically a mixture of beta-lactoglobulin (~65%), alpha-lactalbumin (~25%), bovine serum albumin (~8%)(see also serum albumin), and immunoglobulins. These are soluble in their native forms, independent of pH.
Being a by-product of the cheese making process, and likelihood of animal rennet use, whey protein as well as casein products may not be suitable for consumption by lacto-vegetarians or observers of kosher dietary laws. There are, however, specialty producers of vegetarian-approved whey protein products produced using non-animal "rennet" (enzymes). These products are often also labeled as kosher and halal approved.
The amino acid cysteine in whey protein is a substrate for the synthesis of glutathione in the body which is an ubiquitous cellular antioxidant; laboratory experiments have suggested that whey protein and its components might reduce the risk of cancer in animals, suggesting an avenue for future medical research.
- Concentrates have typically a low (but still significant) level of fat and cholesterol but, in general, compared to the other forms of whey protein, 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. Like whey protein concentrates, whey protein isolates 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.
- Native whey protein, the purest form of whey protein which has been extracted from skim milk and not a by product of cheese production, produced as a concentrate and isolate.
The use of whey protein as a source of amino acids and its effect on reducing the risks of diseases such as heart disease, cancer and diabetes has been the focus of ongoing research as of 2007[update]. Whey is an abundant source of branched-chain amino acids (BCAAs), which are used to stimulate 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).
Scientific evidence has shown that proteins high in essential amino acids (EAA), branched chain amino acids (BCAA), and particularly leucine (Leu) are associated with increased muscle protein synthesis, weight loss, body fat loss, and decreased plasma insulin and triglyceride profile. Whey has approximately three grams of leucine per serving and the threshold for optimal protein synthesis is three grams.
- Marshall, K (2004). "Therapeutic applications of whey protein". Alternative Medicine Review 9 (2): 136–156. PMID 15253675.
- Wal JM (November 2004). "Bovine milk allergenicity". Ann. Allergy Asthma Immunol. 93 (5 Suppl 3): S2–11. doi:10.1016/S1081-1206(10)61726-7. PMID 15562868.
- Burks W, Helm R, Stanley S, Bannon GA (June 2001). "Food allergens". Curr Opin Allergy Clin Immunol 1 (3): 243–8. doi:10.1097/01.all.0000011021.73682.01. PMID 11964696.
- Spurlock, D. "Isolation and Identification of Casein From Milk Course Notes". Retrieved 27 June 2014.
- "Whey." The Encyclopædia Britannica. 15th ed. 1994
- Foegeding, EA; Davis, JP; Doucet, D; McGuffey, MK (2002). "Advances in modifying and understanding whey protein functionality". Trends in Food Science & Technology 13 (5): 151–9. doi:10.1016/S0924-2244(02)00111-5.
- Tunick MH (2008). "Whey Protein Production and Utilization.". In Onwulata CI, Huth PJ. Whey processing, functionality and health benefits (ABSTRACT). Ames, Iowa: Blackwell Publishing; IFT Press. pp. 1–13.
- Lee YH (November 1992). "Food-processing approaches to altering allergenic potential of milk-based formula.". J. Pediatr. 121 (5 Pt 2): S47–50. doi:10.1016/S0022-3476(05)81406-4. PMID 1447634.
- Jay R. Hoffman and Michael J. Falvo (2004). "Protein - Which is best?". Journal of Sports Science and Medicine (3): 118–130.
- Luhovyy BL, Akhavan T, Anderson GH (2007). "Whey proteins in the regulation of food intake and satiety". Journal of the American College of Nutrition 26 (6): 704S–712S. doi:10.1080/07315724.2007.10719651. PMID 18187437.
- Haug A, Høstmark AT, Harstad OM, A; Høstmark, AT; Harstad, OM (25 September 2007). "Bovine milk in human nutrition – a review". Lipids Health Dis 6: 25. doi:10.1186/1476-511X-6-25. PMC 2039733. PMID 17894873.
- P.W. Parodi (2007). "A Role for Milk Proteins and their Peptides in Cancer Prevention". Current Pharmaceutical Design 13 (8): 813–828. doi:10.2174/138161207780363059. ISSN 1873-4286.
- [old info]Krissansen GW (December 2007). "Emerging health properties of whey proteins and their clinical implications". J Am Coll Nutr 26 (6): 713S–23S. doi:10.1080/07315724.2007.10719652. PMID 18187438.
- Rieu I, Balage M, Sornet C et al. (April 2007). "Increased availability of leucine with leucine-rich whey proteins improves postprandial muscle protein synthesis in aging rats". Nutrition 23 (4): 323–31. doi:10.1016/j.nut.2006.12.013. PMID 17367997.
- Kimball Scott; Jefferson, LS (2006). "Signaling Pathways and Molecular Mechanisms through which Branched-Chain Amino Acids Mediate Translational Control of Protein Synthesis". The Journal of Nutrition 136 (1): 227S–31S. PMID 16365087.
- Ha E, Zemel MB (May 2003). "Functional properties of whey, whey components, and essential amino acids: mechanisms underlying health benefits for active people (review)". J. Nutr. Biochem. 14 (5): 251–8. doi:10.1016/S0955-2863(03)00030-5. PMID 12832028.
- Phillips SM (February 2011). "The science of muscle hypertrophy: making dietary protein count". Proc Nutr Soc (Review) 70 (1): 100–3. doi:10.1017/S002966511000399X. PMID 21092368.
- Etzel. "Manufacture and use of dairy protein fractions". J. Nutr. 134: 996S–1002S.
- Hulmi, J. J.; Kovanen, V.; Selänne, H.; Kraemer, W. J.; Häkkinen, K.; Mero, A. A. (2009). "Acute and long-term effects of resistance exercise with or without protein ingestion on muscle hypertrophy and gene expression". Amino Acids 37 (2): 297–308. doi:10.1007/s00726-008-0150-6.
- Whey protein resources, National Dairy Council
- Whey Protein Healthnotes, University of California, San Diego
- What does science say about whey protein and muscle building?, European Food Safety Authority on whey protein claims