Milk-and-Dairy-Products-in-Human-Nutrition-FAO

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Milk and dairy products in human nutrition
Major proteins: casein and whey
Casein, the predominant milk-protein component, is widely accepted to be a valuable
source of amino acids for human growth. Traditionally, whey was considered
the low-value by-product of cheese production, but in recent decades, whey
components have attracted increasing commercial interest (Bulut Solak and Akin,
2012). Whey is the soluble fraction of milk that is separated from casein during
cheese-making and casein manufacture in the dairy industry. The whey fraction
contains a variety of proteins which can be separated by processes such as ultrafiltration
and reverse osmosis to produce whey-protein concentrates. Whey proteins
can be consumed as nutrition bars, powdered beverages or sports meals (Korhonen,
2009a; Hernández-Ledesma, Ramos and Gómez-Ruiz, 2011). Whey proteins, in
addition to delivering amino acids, are reported to be involved in protection against
infections, immune enhancement and development of the gut (Kanwar et al., 2009),
as well as being a source of bioactive peptides. Some reports suggest that the wheyprotein
complex is implicated in satiety and weight management, although it is not
clear whether whey protein has a greater effect than other milk proteins in this
regard (Korhonen, 2009a; Hernández-Ledesma, Ramos and Gómez-Ruiz, 2011;
Mølgaard et al., 2011).
α-lactalbumin, the predominant whey protein in human milk, is important in lactose
synthesis. It has low immunogenicity, in contrast to β-lactoglobulin, which has
been implicated in CMA. Recently, it has been suggested that it may have beneficial
effects on sleep, mood and cognition because of its role in increasing serotonin levels
(Korhonen, 2009a; Camfield et al., 2011). A number of health characteristics have
been suggested for β-lactoglobulin, including antiviral and anticarcinogenic effects
(Chatterton et al., 2006). Lactoferrin, an iron-binding whey protein, has been associated
with positive antimicrobial effects, immune modulation and modulation of
the gut microbiota (Kanwar et al., 2009; Tomita et al., 2009, Nagpal et al., 2012). A
recent meta-analysis on the efficacy of lactoferrin in the eradication of Helicobacter
pylori infection concluded that lactoferrin may have the potential to reduce H. pylori
infection without adverse effects (Sachdeva and Nagpal, 2009). Heliobacter pylori is
the causative agent of peptic ulcer diseases and chronic gastritis and is an important
risk factor for development of gastric cancer (Salih, 2009); the global prevalence of
H. pylori infection is more than 50 percent, mainly in developing countries.
Excessive protein consumption may have adverse human health effects. The rate
at which the gastrointestinal tract can absorb amino acids and the liver’s capacity to
deaminate proteins and produce urea to excrete excess nitrogen are key issues. The
safety and validity of increased protein intakes for both weight maintenance and
muscle synthesis have been subjects of considerable debate and some health professionals,
media and diet books advise consuming diets high in protein despite the
lack of scientific data on the safety of increasing protein consumption (Bilsborough
and Mann, 2006).
Protein fragments: bioactive peptides
Recent research has shown that milk proteins can act as precursors of bioactive peptides,
which are protein fragments varying in size from two to 20 amino acids. These
discrete amino-acid sequences are inactive within the parent protein molecule and
can be released through the action of digestive proteases or via proteolytic enzymes,