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Developed in conjunction with The American Academy of Family
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Dairy Council Digest Archives
Health-Enhancing Properties of Dairy Ingredients
Emerging Health Benefits of Whey Proteins
The traditional role of whey proteins in foods has been to provide dietary nitrogen and amino acids (7). However, in recent years, several additional beneficial physiological roles for whey proteins have been defined or suggested, as discussed below. This scientific field is so new that most of the evidence supporting biological roles for whey proteins has been derived from experimental animal and in vitro studies.
Laboratory animal and in vitro studies indicate that whey proteins have anticarcinogenic and hypocholesterolemic effects, as well as other potential health benefits.
Antibacterial and Antiviral Properties. Lactoferrin consumed in food has been reported to be effective against pathogens such as bacteria, viruses, and fungi (1,7,8,10,24). For example, lactoferrin has been demonstrated to protect against pathogens such as Haemophilus influenzae which causes otitis media (ear infections) in children (25). The antimicrobial effect of lactoferrin was originally linked to its iron-scavenging activity (12), but more recent evidence indicates that at least some of its antimicrobial activity is independent of iron. Bovine lactoferrin, as its peptide fragment lactoferricin (lactoferricin B), directly damages the structure and alters the permeability of gram negative bacterial outer cell membranes (26). As a result, the microbial cells lose their integrity and are killed. The question of whether lactoferricin is produced in the human stomach following intake of food supplemented with bovine lactoferrin has been positively answered in at least one adult (14).
The antimicrobial activity of lactoferricin B is greater than that of lactoferrin (14,27,28). Lactoferricin B has been demonstrated to markedly inhibit the growth of several susceptible organisms including E. coli, Salmonella enteritidis, Klebsiella pneumoniae, Campylobacter jejuni, and Listeria monocytogenes (7,27,29). In vitro studies indicate that bovine lactoferrin and lactoferricin may help to protect against E. coli 0157:H7 which has been associated with large outbreaks of food-borne haemorrhagic colitis (28).
Interestingly, lactoferrin has also been found to protect against a number of different viruses, including cytomegalovirus, influenza, rotavirus, human immunodeficiency virus (HIV), herpes simplex types 1 and 2, and hepatitis C (1,8,30,31).
Immune System Stimulation. Even transient alterations in the immune system can predispose individuals to increased risk of infections and diseases such as cancer, as well as exacerbate existing diseases. Cell culture studies and in vivo investigations of experimental animals have demonstrated that whey proteins enhance non-specific and specific immune responses (7-9,32). The high concentration of cysteine and glutamate in whey proteins, which are precursors for the synthesis of glutathione, is believed to contribute to these immuno-enhancing effects (32-34).
Individual whey proteins such as lactoferrin also have the ability to modulate immune functions (7,8,35). As reviewed by German (7), investigations in laboratory animals indicate that lactoferrin stimulates humoral immune response to sheep red blood cells, promotes appropriate intestinal and peripheral specific antibody response, and modulates the production of lymphokines. A recent investigation found that lactoferrin protected mice against the lethal effects of bacterial lipopolysaccharide (LPS), a powerful endotoxin produced by gram-negative bacteria (36). Consuming lactoferrin increased the survival of mice exposed to LPS by six-fold (36). Potential immunomodulating roles for other whey proteins such as immunoglobulins and GMP have also been demonstrated (8,12).
Antioxidant Action. By supporting antioxidant functions, whey proteins could potentially help to reduce the risk of numerous diseases including cancer and atherosclerosis (9). Whey protein is rich in cysteine and glutamate, precursors for glutathione which, in turn, mitigates oxidative stress (7,8,12,33,34). Glutathione levels in the thymus of rats are higher in animals fed a whey protein diet than in those fed either meat or soy diets (37). Individual whey proteins such as lactoferrin also inhibit oxidation by scavenging free iron, thereby limiting its availability to catalyze oxidative reactions (8).
Anticarcinogenic Activities. Whey protein has been reported to protect against some cancers (7-9,37). In laboratory rats fed whey protein diets, fewer chemically induced colon tumors developed than in rats fed experimental diets containing casein, meat, or soy proteins (38). This effect was attributed to increased tissue concentration of glutathione, which was stimulated by the whey protein diet (33,34,38,39). However, other mechanisms may be involved (37,40).
Individual whey proteins may be anticarcinogenic. When alpha-lactalbumin was incubated with two different mammalian intestinal cell lines, cell division decreased, whereas peptides from fermented casein had no effect on cell division (41). Bovine lactoferrin may also be beneficial in the prevention of some cancers (37,42-46).
Hypocholesterolemic Effect. The effects of dietary whey protein and casein on plasma and liver cholesterol concentrations were investigated in female weanling rats fed a cholesterol-containing diet for three weeks (47). At high protein intakes, whey protein significantly lowered plasma and liver cholesterol, as well as plasma triacylglycerol levels (47).
In another investigation, standard yogurt fortified with condensed whey or lactose-hydrolyzed condensed whey and bifidus yogurts reduced total and low density lipoprotein cholesterol levels in laboratory rats (48). In contrast, whole milk and standard yogurt had no hypocholesterolemic effect (48). One in vivo investigation found that lactoferrin may act as an anti-atherogenic agent by inhibiting the accumulation of cholesterol esters in macrophages (i.e., precursors of foam cells found in early atherosclerotic lesions) (49).
Other Potential Benefits. Whey proteins may potentially provide other health benefits including support of growth, bone health, and weight control. Whey contains several known growth-supporting factors including lactoferrin which may be beneficial for the recovery of tissues following metabolic stress resulting from illness, surgery, or chemotherapy treatment (6,7,50,51). Whey minerals such as calcium, phosphorus, and magnesium support bone growth and maintenance (9). In addition, whey proteins may be beneficial for bone health (52,53). The whey peptide GMP has been reported to stimulate the release of cholecystokinin (CCK). However, further research is necessary to establish whether GMP added to food products enhances postprandial satiety and has a role in weight control.
Dairy ingredients, such as whey proteins, may be particularly beneficial for infants, older adults, some patients, and athletes. However, more research is necessary to substantiate their health benefits in humans.
Importance of Whey Proteins for Special Populations. Hydrolyzed whey protein-based formulas are beneficial for infants with an intolerance to cow's milk protein (7). Also, extensively hydrolyzed whey formula may help reduce excessive crying in infants (i.e., infantile colic) (54). In an effort to develop infant formulas that more closely resemble human milk, researchers are examining the potential of whey protein fractions rich in specific proteins, such as lactoferrin, for their use in infant formula (1,6,8). Lactoferrin, the main whey protein in human milk, is present at a low level in cow milk (8,13,24).
Whey proteins' unique advantages may be particularly appropriate in the diets of older adults. In laboratory mice, intake of a whey-rich diet increased the animals' longevity or survival, as well as liver and heart glutathione levels (33). Whey protein may help maintain health during later years by providing growth-supporting factors which aid the recovery of tissues damaged by injury or surgery, enhance immunity, and regulate smooth muscle cell function which favors gastrointestinal health.
Patients with acute or chronic conditions may benefit from the biological activities of whey proteins (12). Because of the ability of immunoglobulins, lactoglobulins, and bovine serum albumin to enhance immunity, intake of these whey proteins may be beneficial for patients with cancer or AIDS (12). Also, branched chain amino acids found in whey proteins are readily used by muscle for energy during stress which is important for malnourished patients or those who require a protein-restricted diet (e.g., end-stage renal disease) (12).
Branched chain amino acids in whey proteins are beneficial for athletes by helping to minimize muscle wasting under conditions of increased protein catabolism, as occurs with sustained intense exercise (e.g., a marathon) (55). Intake of branched chain amino acids prevented loss of body mass and muscle in 16 athletes who participated in a 21-day hike at high altitude (56). Also, consuming a moderate energy restricted diet rich in branched chain amino acids allowed wrestlers to lose abdominal visceral adipose tissue without compromising their high level of performance (57). These observations support the performance value of whey proteins in sports nutrition foods and beverages (7).
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