Immunoglobulin is an important protein that usually has antibody activities. The main immunoglobulin IgG constitutes approximately 75% of the antibodies in human adults. IgG is transferred from mother to child in utero via cord blood and by breast‐feeding to serve as a child’s first line of immune defense.
Another type of immunoglobulin IgA is transferred from breast milk to the digestive tract of the newborns. Therefore, one advantage of breastfeeding is to provide more immune factors than that of a bottle‐fed child so to better prevent the intestinal colonization of gram‐negative enterobacilli(Bonang et al. 2000).
Interestingly, the whey fraction of milk contains a significant amount of immunoglobulins that account for approximately 10–15% of total proteins. Bovine milk derived immunoglobulins may have the potential to modulate immune responses in humans. Bovine milk IgG at concentrations as low as 300 μg ml−1 can completely suppress the synthesis of IgG, IgA, and IgM (96–98% suppression) as well as the mitogenic response in human cell cultures. Moderate heating (63 °C during 30 minutes) of IgG can increase its suppressive effect (Kulczycki and Macdermott 1985). Therefore, milk is likely to confer immunity in humans. Raw milk from non‐immunized or immunized cows contain specific antibodies that have sufficient immune activity against the lipopolysaccharides of bacterial pathogens (Losso et al. 1993). The IgG antibody in raw milk and pasteurized milk can protect from infection and diseases in mice of rotavirus infections (Yolken et al. 1985).
LF also plays a critical role in the immune system of the body. For example, seven‐day treatment by applying LF in addition to the widely used triple therapy (rabeprazole, clarithromycin, tinidazole) was effective in eradicating Helicobacter pylori (H. pylori)(Di Mario et al. 2003). Another good example is treatment of patients infected with group A streptococciusing LF, which has similar behavior as the other facultative intracellular bacterial pathogens that enter and survive within host cells without evidence of intracellular replication to avoid the host defense and contribute to the recurrence of infections when the surrounding conditions allow. The bovine LF has been shown to be able of decreasing group A streptococciinvasion both in vitroand in vivo(Ajello et al. 2002).
Two weeks’ supplementation of whey protein greatly increased lymphocyte proliferation of peripheral blood mononuclear cells that helped maintain an athlete’s health during heavy training or competition (Shute 2004). Whey protein has the capacity to enhance or “prime” human neutrophil responses to a subsequent stimulation through β‐LG and α‐LA (Rusu et al. 2009). From above, we conclude that whey protein also has great potential to modulate the immune system that is much helpful in the treatment for many patients with immunity related diseases.
In addition to whey protein’s strong functional properties, such as solubility, foaming, emulsification, and gelation, it also has demonstrated promising physiological activity such as antioxidant activity, antibacterial activity, immunomodulatory effects, antitumor activity, and muscle growth (Yadav et al. 2015). The antioxidant activity of whey protein is very popular at present, due to its ability to treat aging and enhance whole body immunity. In brief, biochemical reactions in the body generate reactive oxygen species (ROS) and free radicals, which can enhance oxidative damage to various biomolecules of DNA, proteins and small cellular molecules, and lead to several disease conditions if left untreated. The harmful action of the free radicals can be blocked by antioxidants, which scavenge the free radicals and eliminate their damaging effect on cellular constituents. Natural antioxidants from whey protein, including peptides and its modification products, have been shown to increase the antioxidant capacity of the plasma and reduce the risk of certain diseases such as cancer, heart disease, and stroke (Yao et al. 2016). Whey protein compounds have also been shown to modulate adiposity, and to enhance immune function (Schröder et al. 2017). Therefore, the antioxidant activity of whey protein presents new applications in prevention of disease. The antioxidant activity of total whey protein and its derivatives are described in the subsequent subsections.
Cardiovascular disease is a collection of diseases that involve the heart and/or blood vessels with various mechanisms. Food derived nutraceuticals hold promise in pharmaceutical treatment of the cardiovascular disease. Emerging research indicates that whey protein may reduce cardiovascular disease risk factors. For example, fermented milk supplemented with WPC improved the lipid profile and decreased the systolic blood pressure of humans, which indicated that whey protein had potential to reduce the risk of cardiovascular diseases (Kawase 2000). Major cardiovascular diseases are strongly associated with obesity (Lavie et al. 2009). Whey protein after hours’ ingestion reduced approximately 30% of the plasma triglycerides compared to the casein in over- weight post‐menopausal women (Pal et al. 2010). Whey protein preloads 30 minutes before ad libitum main meal for several weeks showed stronger beneficial effects than soy protein preloads on blood pressure, fast glucose level and lipid profile in overweight and obese men (Tahavorgar et al. 2015; Golzar et al. 2012).
Patients with elevated blood pressure are commonly treated pharmacologically by inhibiting angiotensin‐converting enzyme (ACE). ACE is a key enzyme in the regulation of blood pressure and thus is an important factor for cardio- vascular disease. Inhibition of ACE activity prevents the conversion from angiotensin I to angiotensin II. Therefore, the mechanism of whey protein to reduce cardiovascular risks is probably attributed to the peptides derived from whey protein that have ACE inhibitory effect (Pan et al. 2012; Cvander et al. 2002; Zhao et al. 2002). Future research is needed to focus on the molecular pathways involved.
Whey protein can protect the liver from damage and infections. Hepatitis C virus is a virus that causes hepatitis C and increases the risk of cirrhosis, some cancers and lymphomas in humans. Whey protein components have positive impact on patients with hepatitis C. The bovine LF – one member of the iron transporter family can effectively prevent hepatitis C virus infection in cultured human hepatocytes (Ikeda et al. 1998). A follow up study showed that eight weeks’ supplementation of LF decreased the serum alanine transaminase and hepatitis C viral RNA concentrations in patients with chronic hepatitis (Tanaka et al. 1999). Further research is needed to find out the optimum dose in combination with conventional treatments. Another study showed that whey protein can improve liver functions in patients with chronic hepatitis B, which further suggests its potential in clinical use as adjunctive therapy (Watanabe et al. 2000).
Glutathione deficiency can lead to liver injury and even cause steatohepatitis. As expected, whey protein can alleviate the liver damage by GSH generation due to its cysteine‐rich amino acid profile (Balbis et al. 2009). Whey protein ameliorates the oxidative stress that has long been recognized to be the main cause responsible for liver damage and disease exacerbation (Bonnefont‐ Rousselot et al. 2006). Indeed, oral supplementation of WPI result in improve- ment in liver biochemistries, increased plasma GSH, high antioxidant capacity and reduced hepatic macrovascular steatosis in patients with nonalcoholic steatohepatitis (Chitapanarux et al. 2009).