Designer Milk for Human Health: A Future Need
Amit Kumar Verma,
Recently there is a rising interest in dairy biotechnology for altering the composition of milk by nutritional and genetic manipulations for the well being of human. These alterations are in milk fat, milk protein, lactose contents, humanization of bovine milk, adding therapeutic proteins etc. For acceptance of this designer milk we have to address certain ethical, legal and social aspects along with economic production of designer milk.
March 17, 2012; Accepted: May 02, 2012;
Published: July 10, 2012
Milk is a natural complete food, which provides fat, protein, essential vitamins
and minerals and also a good source of calcium that is essential for the prevention
of bone disorders such as osteoporosis (Gulati et al.,
2000). With the changing social and eating behaviour, the milk should be
of special value so that it can compete with other dairy products and energy
drink. For this milk have to be designed in such a way, which increase its properties
according to the need of the changing scenario. Designing of the milk means
production of the milk that has certain specific values viz., improve the immunity,
utilization of lactose and alleviate diarrhoea. Low fat, more protein, less
lactose, changed amino acid and fatty acid profiles and without b-lactoglobulin
are important properties of designing milk for human health point
of view. Designer milks will give improved and value added products naturally
with improved nutraceuticals to meet the requirements of the new millennium.
Now a days biotechnologists have identified genetic markers in cows for
disease or desirable traits such as milk fat synthesis. So, in future we can
expect the cows that will produce low fat milk naturally, which can be achieved
through combinations of traditional genetics, marker-assisted selection and
genetic modification of dairy cattle and by farm and feed management. From human
health point of view some of the desirable improvements are-(1) Increased proportion
of unsaturated fatty acids and low fat milk and its products, (2) Low lactose
content and (3) complete absence of b-lactoglobulin from milk.
ALTERATION IN MILK FAT
The consumption of full cream milk is declining due to high proportion of saturated
fats (i.e., 60%), which leads to increase in LDL (low density lipoprotein) in
blood, a risk factor for heart disease (Noakes et al.,
1996). Milk fat designing means producing milk with low in fat particularly
low saturated fat and increased linoleic acid in milk fat. This can be designed
by change in feed for dairy animals and genetic interventions. Feeding rumen
protected fat supplements enables the dairy animals to produce milk products
containing structurally important dietary fats that are required for specific
biological activities such as vision and neural development, antioxidants, anticancer
substances and the dietary modification of genetically linked disorders viz.,
heart diseases. Feeding protected canola/soybean in ratio of 70/30 w/w significantly
increased the proportion of C18:1 cis (oleic acid), C18:2 (linoleic acid) and
C18:3 (linolenic). Similarly, protected soybean/tuna oil ( ratio 70/30; w/w)
significantly increased the proportion of C18:2 (linoleic acid), C18:3 (linolenic),
C20:5 (EPA-eicosapentaenoic acid) and C22:6 (DHA; docosahexaenoic acid) while,
feeding conjugated linoleic acid (CLA)/casein (1:1; w/w) supplements protected
from ruminal hydrogenation increased the CLA isomers 9 cis 11 trans, 10 trans
12 cis. There was a reduction in the C16:0 (palmitic acid) by feeding protected
supplements (Gulati et al., 2000). The alternative
method to increase milk fat is selection of cattle based on DGAT1 genotype,
which code for acyl-coenzyme A: diacylglycerol acyltransferase 1, is located
on chromosome 14 in cattle (Grisart et al., 2002;
Winter et al., 2002) and plays important role
in synthesis of triacylglycerol.
ALTERATION IN MILK PROTEIN
Casein is main milk protein. Through genetic engineering, transgenic cows secreting
elevated levels of b-(8-20%) and k-caseins (twofold) have been produced (Brophy
et al., 2003). Brophys group produced the transgenic animals,
which have increased total milk protein by 13-20% and total milk casein by 17-35%
in comparison to than that of non-transgenic cows. b-casein is the most abundant
milk protein which is involved in binding calcium phosphate and controlling
milk calcium levels. Higher k-casein content in milk is linked to smaller micelles,
better heat stability and improved cheese-making properties. Adding L-taurine,
L-leucine and L-phenylalanine in feed improved amino acid profile, which is
another additional benefit.
MODIFICATION IN LACTOSE
The enzymatic hydrolysis of lactose is done by β-galctosidase into glucose and galactose and then their absorption into blood. In human beings, the level of β-galctosidase declines from early childhood to adolescent. When such adult ingest milk or their products, the lactose remain undigested leading to malabosrbtion, which further increase the water retention in gut and bacterial proliferation upset the gastrointestinal tract, which will lead to diarrhoea and dehydration. Since, milk is an important component of human diet especially for calcium, so lactose intolerance can limit this source. In later stage, this may cause bone disorders like osteoporosis.
HUMANIZED BOVINE MILK
It is well established that mothers milk is best for the newborn baby. In many of cases if there is non-availability of mothers milk than it can be replaced by cows milk. But the composition of human milk and bovine milk differ in many aspects. One of them is lactoferrin (LF), the iron binding protein having antimicrobial property and role in regulating immune system. Its level in human milk is about 1 g L-1 (in human colostrum 7 g L-1) while in bovines milk it is only one-tenth than that of human milk.
REDUCING MILK ALLERGIES
In a study conducted on African and Americans (age group 12-40 years) the lactose
content of milk was not the cause of cause of milk intolerance in one third
of human beings (Johnson et al., 1993). In children,
milk allergy to bovines milk is due to b-lg, which is absent in human
milk. Thus, elimination of this protein by knocking out gene responsible for
b-lg from bovines is unlikely to have any detrimental effects on bovine and
might overcome milk allergy problems associated with bovine milk.
MILK AND THERAPEUTICS
Scientists are trying to produce the proteins that can be helpful in human therapeutics. In this regards GTC Biotherapeutics (Framingham, MA) uses both cows and goats for the production of therapeutic proteins, including plasma proteins, monoclonal antibodies and vaccines. Recently, recombinant human antithrombin III has been produced in goat milk, which is an anti-coagulant protein in blood. Researchers are also working on production of vaccine against malaria from goat milk, which can be cheaper than current methods. With the use of biotechnology, it might be possible in future to produce specific antibodies (against Salmonella, E. coli and Listeria etc.) in mammary tissue that can prevent its own infection as well as helpful in preventing the disease in human beings and treating the diseases such as phenylketonuria (PKU), hereditary emphysema and cystic fibrosis. With the help of bioengineering, goat can be used in the production of spider silk in its milk that can be of immense help for preparing medical micro sutures and tennis racket strings.
Despite all these promising prospects, there is a tendency among human beings to resist change, especially those of transgenic. Thus, the future of biotechnologically modified foods is at crossroads even after three decades of promising results. Various ethical, legal and social issues should be solved before we would go for designer milk similar to organic herds. The future of the dairy industry is not just about producing more and more milk, but about producing more milk of the right kind. Thus, we can expect that in future dairy farmers may be the producers of designer milk.
Brophy, B., G. Smolenski, T. Wheeler, D. Wells, P. L'Huillier and G. Laible, 2003. Cloned transgenic cattle produce milk with higher levels of β-casein and κ-casein. Nat. Biotechnol., 21: 157-162.
CrossRef | Direct Link |
Grisart, B., W. Coppieters, F. Farnir, L. Karim and C. Ford et al., 2002. Positional candidate cloning of a QTL in dairy cattle: Identification of a missense mutation in the bovine DGAT1 gene with major effect on milk yield and composition. Genome Res., 12: 222-231.
Gulati, S.K., S.M. Kitessa, J.R. Ashes, G. Simos, P. Wynn, E. Fleck and T.W. Scott, 2000. Designing milk fat for the new millennium by dietary strategies. Asian Aust. J. Anim. Sci., 13: 538-541.
Direct Link |
Johnson, A.O., J.G. Semenya, M.S. Buchowski, C.O. Enwonwu and N.S. Scrimshaw, 1993. Correlation of lactose maldigestion, lactose intolerance and milk intolerance. Am. J. Clin. Nutr., 57: 399-401.
Direct Link |
Noakes, M., P.J. Nestel and P.M. Clifton, 1996. Modifying the fatty acid profile of dairy products through feedlot technology lowers plasma cholesterol of humans consuming the products. Am. J. Clin. Nutr., 63: 42-46.
Direct Link |
Winter, A., W. Kramer, F.A.O. Werner, S. Kollers and S. Kata et al., 2002. Association of a lysine-232/alanine polymorphism in a bovine gene encoding acyl-CoA: Diacylglycerol acyltransferase (DGAT1) with variation at a quantitative trait locus for milk fat content. Proc. Natl. Acad. Sci., 99: 9300-9305.
CrossRef | Direct Link |