REVIEW

Nutritional Functions of Milk and Dairy Products in Improving Human Health

Jung-Whan Chon1,2,, Hyunsook Kim3,, Dong-Hyeon Kim1,, Soo-Kyung Lee1,, Hong-Seok Kim1,, Jin-Hyuk Yim1, Kwang-Young Song1,*, Young-Ji Kim1, Il-Byung Kang1, Dana Jeong1,, Jin-Hyeong Park1, Ho-Seok Jang1, Kun-Ho Seo1,
Author Information & Copyright
1Center for One Health, College of Veterinary Medicine, Konkuk University, Seoul, Korea
2National Center for Toxicological Research, US Food and Drug Administration, Jefferson, USA
3Dept. of Food & Nutrition, College of Human Ecology, Hanyang University, Seoul, Korea
*Corresponding Author : Young Min Choi, Dept. of Obstetrics & Gynecology, College of Medicine, Seoul National University, Seoul 03080, Korea. Tel. :+82-2-2072-2385, Fax : +82-2-3672-7601, E-mail : drkysong@gmail.com

† These authors contributed equally to this study.

ⓒ Copyright 2016, Korean Society of Milk Science and Biotechnology. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Jul 05, 2016 ; Revised: Jul 28, 2016 ; Accepted: Aug 01, 2016

Published Online: Sep 30, 2016

Abstract

Cow’s milk and dairy products are elements of the human diet that could play an important role in improving human health. The macronutrients and micronutrients found in milk could supply the nutrients required to maintain human health. Among them, milk-derived bioactive peptides have been identified as potential ingredients found in health promoting functional foods. These bioactive peptides target diet-related chronic diseases, particularly non-communicable ones such as cardiovascular disease, diabetes and obesity. Additionally probiotics such as lactic acid bacteria (LAB) are can be considered live microorganisms that confer health benefits for the host-, when administered in adequate amounts. Further, the calcium, vitamin D, and protein content of milk and dairy products could play a role in proving bone health. The effect of milk and calcium on bone mineral density could prevent against fracture, osteoporosis and rickets. Furthermore, milk and dairy products also contain which factors that, which protect against dental caries (anti-cariogenic properties). This paper reviews the various nutritional functions of milk and dairy products in improving human health.

Keywords: milk; calcium; bioactive peptide; probiotic; dental; health

Introduction

Now, the cow has become the main dairy animal associated with milk, with the term “milk” being almost synonymous with cow’s milk in most people’s minds. In fact, domestication of animals for livestock has played a key role in the development of human civilizations (Doreau and Martin-Rosset, 2002).

Milk production began 6,000 years ago or even earlier. The dairy animals of today have been developed from untamed animals which, through thousands of years, lived at different altitudes and latitudes exposed to natural and, many times, severe and extreme conditions (Rogelj, 2000). Now, the dairy industry is an essential part of agricultural policy in most countries, and these policies have resulted in the breeding of high producing stock and the development of effective and safe milk collection and delivery systems (Fox, 2008). The compositions of different types of milk are given in Table 1.

Table 1. Composition of milk from different animals (per 100 mL)
Protein (g) Fat (g) Lactose (g) Calcium (mg) Water (g) Energy (kJ)
Human 1.3 4.1 7.2 34 87 289
Cow 3.3 3.9 4.5 118 88 274
Buffalo 4.1 5.9 5.9 175 83 385
Goat 3.1 3.7 4.4 100 89 260
Sheep 5.4 5.8 5.1 170 83 388
Camel 2.0 4.1 4.7 94 89 264

Source : Fox, 2008

Download Excel Table

According to outlook of milk consumption around the world, there has been a modest increase in the per capita consumption of milk since 1965 from 74 to 78 kg/person/year. This is predicted to rise to 90 kg/person/year by the year 2030, with rises expected in all threecategories of country (industrialized, transitional and developing) (Table 2). In terms of global importance, the increases (1965 to 1998) and the predicted increases (1998 to 2030) in East Asia and South Asia are the most significant, because of their large populations. The predicted increase in Latin America and the Caribbean is also substantial (WHO, 2003). And according to annual report of FAO, the demand for milk in developing countries is expected to increase by over 25 percent by 2025 (FAO, 2008).

Table 2. World trends in milk consumption (kg/person/year)
1965 1998 2030
World 74 78 90
Developing countries 28 45 66
① Near East & North Africa 69 72 90
② Sub-Saharan Africa 29 29 34
③ Latin America & Caribbean 80 110 140
④ East Asia 4 10 18
⑤ South Asia 37 68 107
Transition countries 157 159 179
Industrialized countries 186 212 221
Download Excel Table

Until now, milk has been part of the human diet for millennia and is valued as a natural and traditional food (Merritt et al., 2006). Milk and dairy foods are considered to be one of the main food groups important in a healthy balanced diet, and as such feature in the majority of national food-based dietary guidelines. Hence, for understanding various positive effects about milk, (1) composition of milk and dairy product, (2) several bioactive peptide derived from milk, (3) fermented milk products, (4) bone health and milk & dairy products, and (5) oral health and dietary dairy have been described in this review paper.

Cow’s Milk

Traditionally, milk is a major source of dietary energy, protein and fat (FAOSTAT, 2012). Milk is a composite liquid that provides nutrients and biological active compounds which enhance the postnatal adaptation of newborn by improving the digestive maturity, development of gut-associated lymphoid tissues and synbiotic microflora (Ebringer et al., 2008). Milk also contains antibodies which protect the young mammal against infection. A calf needs about 1,000 litres of milk for growth, and that is the quantity which the primitive cow produces for each calf. There has been an enormous change since man took the cow into his service. Selective breeding has resulted in dairy cows which yield an average of more than 6,000 litres of milk per calf, that is to say six times as much as the primitive cow. Some cows can yield 14,000 litres or more. Before a cow can start to produce milk she must have calved first. Heifers reach sexual maturity at the age of seven or eight months but are not usually bred until they are 15 – 18 months old. The period of gestation is 265 – 300 days, varying according to the breed of cow, so a heifer produces her first calf at the age of about 2 – 2.5 years (Fox, 2008).

Up to now, approximately 35 percent of dairy cows (about 70 million head) belong to the Holstein-Friesian breed. The popularity of this breed is largely because of its high average milk production (Fox, 2008) and superior ability to convert feed into protein (Buchanan, 2002). Cow’s milk accounted for 83 percent of global milk production in 2010 (FAOSTAT, 2012).

Also, milk could be classified according to its fat content, for example as whole milk, skimmed milk, semi-skimmed milk, low-fat milk and standardized milk. Also It could be classified according to the processing procedures in has undergone, such as pasteurized milk, sterilized milk, ESL (extended shelf-life) milk and UHT (ultra-high-temperature)-treated milk, among others (FAO and WHO, 2009) (Table 3).

Table 3. Milk’s classification by different treatment or processing method
Processing type of milk Specific type of milk
Liquid milk Cow milk, whole, fresh
Milk skim of cows
Standardized milk
Reconstituted milk
Fortified milks
Condensed milk Whole milk, condensed
Skim milk, condensed
Dehydrated milk products Evaporated milks Whole milk, evaporated
Skim milk, evaporated
Dry milk/milk powder Milk whole dried
Milk skimmed dried
Dry whey
Dry buttermilk
Heat-treatments carried out on milk(Microbiocidal measures) Thermization
Pasteurization (LTLT)
Pasteurization (HTST)
UHT treatment
Commercial sterilization
Download Excel Table

Next, among various components, cow’s milk contains approximately 3.5% protein of which 80% are casein and 20% whey proteins. Caseins have been classified as α-, β- and κ-caseins, and also whey contains alactalbumin, β-lactoglobulin and several minor proteins with different biological activities such as enzymes, mineral-binding properties and immunoglobulins (Daniel et al., 1990). The Biologically active peptides in the protein sequence could be defined as fragments that remain inactive in precursor protein sequences. However, when released by the action of proteolytic enzymes, they could interact with selected receptors and regulate the body’s physiological functions (Meisel and Bockelmann, 1999). The activity of peptides is based on their inherent amino acid composition and sequence, and the size of bioactive peptide sequences known to possess multi-functional properties could vary from two to twenty amino acid residues (Meisel and FitzGerald, 2003). Up to now, the multi-functional properties of biologically active milk peptides are increasingly acknowledged. Especially, it could show a positive impact on human’s physiology and metabolism either, directly or through enzymatic hydrolysis in vivo or in vitro (Kitts and Weiler, 2003). The protease enzymes are naturally occurring in food products (for example, milk plasmin), hydrolyze proteins and release bioactive fragments during processing or storage. Furthermore, in case of producing various fermented food products and occurring naturally in the gastrointestinal tract, many types of bacteria could be producing biologically active peptides. For example, cheese contained phospho peptides, and it would be further proteolyzed during the processing of cheese ripening. Eventually it could contribute to form the angiotensin- converting-enzyme (ACE) inhibitors (Saito et al., 2000). The various biologically active peptides derived from milk are initially found in inactive form within the sequence of the precursor molecules, however it could be released in three ways as follows; (i) the enzymatic hydrolysis with digestive enzymes such as chymotrypsin, pepsin, trypsin, and so on; (ii) the fermentation of milk with proteolytic starter cultures; (iii) the proteolysis by enzymes derived from proteolytic microorganisms (Korhonen and Pihlanto, 2003). In other words, when these bioactive peptides are liberated, they could serve to influence numerous physiological responses including cardiovascular, digestive, endocrine, immune & neurological activity, and so on (Table 4).

Table 4. The various multi-functional roles of bioactive peptide derived from milk in the body system
Body system Functional roles
Bioactive peptide derived from milk Bone health Ca binding peptideLactoferrin
Cardiovascular system ACE inhibitory peptideAnti-cholesterolemicAnti-hypertensive85Anti-thrombotic
Digestive system Antimicrobial peptideImmunomodulatoryOpioid
Immune defense CytomodulatoryImmunomodulatory
Nervous system Opioid peptide
Weight management OpioidSatiety inducing Glycomarcopeptide
Download Excel Table

Owing to such various physiological versatilities mentioned above, the attention of many researchers worldwide would be focused on the research of the milk-derived bioactive peptides so as to formulate several potential new drugs with nutraceutical supplement properties, health promoting functional foods or other pharmaceutical products (Korhonen and Pihlanto, 2003; FitzGerald and Meisel, 2003). Therefore, the protein in cow’s milk is of high-quality (defined as protein that supports maximal growth), containing a good balance of all the essential amino acids, including lysine. Since many human diets are deficient in certain essential amino acids (WHO, FAO and UNU, 2007).

Fermented Milk and Dairy Products

Until now, there are more than 3 500 traditional, fermented foods worldwide (EUFIC, 1999). Fermented milk products have been reported to have a positive effect on the human digestive system (Donovan, 2006).

For several thousand years, people have been consuming fermented milks. It is an old consideration that they are health beneficial. They itself have all the milk components modified by lactic acid bacteria (LAB) fermentation (Ebringer et al., 2008). Lactic acid is produced by fermentation of lactose. It minimizes the pH, affects the casein physical properties and consequently enhance digestibility (Fig. 1). Recently, lactic acid bacteria as probiotics have been widely used in producing various fermented milk, therefore, the interest in lactic acid bacteria as probiotics has been increased. In general, probiotics could be defned as “living microorganisms, which upon ingestion in certain numbers, exert health benefits beyond inherent basic nutrition” (Tannock, 2002) but interest in this area was initiated by Metschnikov 100 years ago (Metschnikoff, 1907). Most probiotic microorganisms belong to Lactic Acid Bacteria (LAB). As for the dose of probiotics, it is important to achieve an optimal mass of probiotic in order to survive and colonize the gut, proliferating in adequate amounts, to confer a health benefit. The evidence suggests this dose should be minimally 106 to 107 CFU (colony-forming units) in each gram of product (Rautava et al., 2002).

jmsb-34-3-145-g1
Fig. 1. The various physiological functions of Probiotics as lactic acid bacteria Source : Santosa et al., 2006
Download Original Figure

Also, it could meliorate the usage of calcium and different other minerals and suppress the development of potentially injurious bacteria. Furthermore, fermented milk could be endured by individuals having a reduced ability for lactose digestion due to its smaller lactose content (McBean, 1999), and protein degradation is due to the effect of proteolytic activity of LAB that results in some bioactive peptides and free amino acids. In fact, the bioactive peptides are a common supplement to various functional foods. Among them, milk proteins are the major resource of a variety of biologically active peptides (casokinins, casomorphins, immunopeptides, lactoferricin, lactoferrin, phosphopeptides, and so on) (Dunshea et al., 2007). Several bioactive peptides derived from milk protein are inactive inside the parent protein sequence and could be generated by enzymatic proteolysis in food processing or gastrointestinal digestion (Parvez, et al., 2006). In recent years, multiple reports have described beneficial effects from various aspects on important diseases. Anti-microbial activity, anti-thrombotic activity, blood pressure regulation, immunomodulation and mineral (or vitamin) binding are the major biological activities of such peptides (Fig. 1). Also, the fermented milks are main source of whey proteins such as immunoglobulins, lactalbumin, lactoglobulin, lactoferrin, lactoperoxidase, and so on (McIntosh et al., 1998). These proteins have exhibited a number of biological effects having various effects on the functions of digestion and anti-carcinogenic activities (McIntosh et al., 1998). During the process of fermentation, the digestibility of fat could be also improved. Even though high percentage of saturated fatty acids (FAs) is present in milk fat, it is frequently advised to avoid its use as it leads to coronary heart disease and an atherogenic profile of blood (Shah, 2007). Among the several different saturated FAs in milk, only three FAs - palmitic, myristic and lauric acids- could have the property to raise the blood cholesterol level, however, the one third of the unsaturated FAs could have the tendency to decrease the cholesterol’s level (Shortt et al., 2004). Moreover, fermented milks contain components that are also protective effect. These comprise conjugated linoleic acid (CLA), linoleic acid, calcium, probiotic bacteria or lactic acid bacteria and antioxidants (Fig. 1) (Rogelj, 2000). When the milk fat comprises of several components such as butyric acid, carotene, CLA, ether lipids sphingomyelin and vitamins A & D, it could show anti- carcinogenic effects. Several animal studies reveal that fermented milk inveterate the anti-carcinogenic action of CLA as well as its part in atherosclerosis prevention and in modulation of immune system (MacDonald, 2000).

Bone Health and Milk & Dairy Products

Recently, calcium absorption would be the most interesting content. In general, the mineral profiles in milk and bones have much in common. With the exception of small fish that are eaten whole, including the bones, few foods naturally contain as much calcium as milk (Weaver et al., 1999; Theobald, 2005). Calcium in milk has a high bioavailability, similar to calcium carbonate, which is readily absorbed (Theobald, 2005). Milk is the major source of vitamin D in the diet in countries where milk is fortified with this vitamin, for example, the United States and Canada (USDA and USDHHS, 2010). Dairy products are also a source of dietary protein. Analyses of food sources of calcium, vitamin D, protein, phosphorus and potassium in Americans reveal milk to be the number one single food contributor of most of these bone-related nutrients (Rafferty and Heaney, 2008).

On basis of the known effects of individual nutrients on calcium status, one could speculate that intake of foods such as yoghurt and milk would be advantageous (Weinsier and Krumdieck, 2000) (Table 5). Especially, potassium administration has been found to decrease urinary hydroxyproline and increase serum osteocalcin, suggesting reduced bone resorption and increased bone formation. New et al. (1997) found that food which has a high potassium contents predicted greater bone density at all 4 bone sites measured. Hence, the difference in potassium content among dairy products would be important and also it should be considered (Table 5).

Table 5. The nutrient components of various dairy products (Unit: per 100 g)
Type of dairy products Calcium(mg) Protein(mg) Sodium(mg) Potassium(mg)
Milk Skim 123 3,000 51 166
Yoghurt Nonfat 199 6,000 77 255
Cheese Cheddar 729 25,000 629 100
American 443 21,000 1,450 164
Cottage 61 12,000 406 1
Download Excel Table

The benefits to bone health of including dairy products in the diet or risks of excluding dairy products vary with the life stage. The relationship between milk & dairy products and bone mineral content and bone mineral density (BMD) was reviewed by US Department of Health and Human Services and US Department of Agriculture (USDHHS and USDA, 2005), which found that milk, foods fortified with dairy calcium and calcium supplements all had comparable effects, increasing skeletal mass in younger subjects and reducing loss of skeletal mass in older subjects. However, skeletal benefits of dairy calcium would persist longer than those derived from calcium supplements (USDHHS and USDA, 2005). Also, increased dietary calcium/dairy products, with and without vitamin D, significantly increased total body and lumbar spine bone mineral content in children with low dietary calcium in takes (450–746 mg/day) at baseline (Huncharek et al., 2008). In adolescents, controlled feeding studies with a range of calcium intakes show that dietary calcium explains 12–22 percent of the variation in skeletal calcium acquisition in girls and boys (Braun et al., 2007; Hill et al., 2008). In adolescent girls, bone mineral density (BMD) has been shown to increase by up to 10 percent when 700 mg of supplemental calcium was provided in the form of dairy products, compared with an increase of 1–5 percent when the same quantity of calcium was provided as a calcium supplement, suggesting that supplementation with dairy products has a greater effect on bone health than do calcium supplements (Kerstetter, 1995).

In a two-year randomized controlled trial (RCT), early pubertal girls receiving 1 g calcium from cheese had greater thickness of the cortical shell of the tibia than girls receiving the same amount of calcium from calcium carbonate or who received a placebo (Cheng et al., 2005). According to a seven-year intervention study, Matkovic et al. (2005) found that calcium supplementation (about 670 mg/day beyond a habitual dietary calcium intake of about 830 mg/day, giving a total calcium intake of about1 500 mg/day) affected BMD during the pubertal growth spurt but had a diminishing effect thereafter because of the catch-up phenomenon in bone mineral accretion. By young adulthood, significant effects of calcium supplementation were present at metacarpals and at the proximal forearm in subjects who had better calcium compliance and in subjects who developed larger body frames (Matkovic et al., 2005). In another study, gain in bone mineral mass in prepubertal girls was followed up three to five years after discontinuation of calcium supplementation with calcium phosphate extracted from milk incorporated in various foods, which provided on average a calcium supplement of about 850 mg/day (Bonjour et al., 2001). The authors concluded that this form of calcium phosphate taken during the prepubertal period can modify the trajectory of bone mass growth and cause a long-standing increase in bone mass accrual that lasts beyond the end of supplementation. Most RCTs in older adults use calcium and vitamin D supplements rather than dairy products (Elders et al., 1994). In one trial involving postmenopausal women that did use dairy products, adding 24 oz. of milk per day (giving a mean calcium intake during milk supplementation of 1,471 mg/ day) suppressed bone turnover and improved calcium absorption resulting in an improvement in calcium balance (Recker and Heaney, 1985).

Dairy product consumption would have particular protective effects on women taking oral contraceptives (OC). In young OC users aged 18–30 years with a habitual calcium intake of less than 800 mg/day, increasing calcium intake to 1,000-1 100 mg/day or 1,200-1 300 mg/day) using dairy products (with an emphasis on non- and low-fat milk) protected against loss of hip and spine BMD (Teegarden et al., 2005). The authors speculate that an increase in calcium absorption mediated by an increase in calcitriol (1,25-dihydroxyvitamin D) levels may explain the positive response in bone accrual noted in OC users after dairy product intervention compared with non-OC users.

Based on these studies, Weaver (2008) concluded that advantage in bone gains due to intervention generally disappeared when calcium supplements were used, but not when the intervention was dairy. Although bones may be more responsive to lifestyle choices in young people rather than later on in life, a meta-analysis showed that in premenopausal women of 18–50 years old a calcium intake of 1,000 mg/day or more was positively associated with bone mass (Welten et al., 1995). Consuming extra dairy products for three years increased calcium intake to an average of 810–1,572 mg/day, reduced vertebral BMD loss in premenopausal women (Baran et al., 1990). Furthermore, short-term treatment-related changes in bone turnover markers, especially bone formation, were strongly associated with subsequent changes in BMD (Tu et al., 2015). This could suggest that serial measurement of bone turnover shortly after initiation of kefir therapy may be helpful in assessing the ultimate therapeutic response to kefir-fermented milk (Tu et al., 2015).

Thus, dairy products represent a distinct group, presumably because of their relatively high calcium content. Calcium is considered to be important for bone health. Furthermore, Nordin et al. (1987) suggested that age-related bone loss may be more attributable to excessive calcium loss than to inadequate calcium intake. Accordingly, greater attention needs to be given to eliminating the causes of calcium loss, which in turn should lower calcium requirement (Weinsier and Krumdieck, 2000).

Oral Health and Milk & Dairy Products

In general, dental disease is the most common cause of tooth loss in developed countries (USDHHS, 2000). Tooth decay is an increasing problem in developing countries as diets change to include more sweet and processed foods (Aimutis, 2004). Since the late 1950s, milk was believed to have a protective effect on tooth enamel (Shaw et al., 1959; Jenkins and Ferguson, 1966). Milk has been suggested to have a protective effect against sugar when consumed together (Johansson and Lif Holgerson, 2011) (Table 6).

Table 6. The potential functional mechanisms of the maintenance of dental health through enamel-protective and anti-caries effects by various milk and dairy product
Type of milk and dairy products Potential functional mechanism for enamel-protective and anti-caries effects
Casein Caseins, which account for the largest percentage of milk proteins (80%), contain bioactive peptides. They are thought to have a beneficial effect on cariogenesis via two mechanisms:
1. Prevention of demineralization
2. Inhibition of bacterial attachment and/or biofilm formation
A complex of casein phosphopeptide and amorphous calcium phosphate is formed upon digestion of milk and inhibits dental caries lesions by increasing the level of amorphous calcium phosphate in dental plaque so as to depress enamel demineralization and enhance remineralization.
The adherence of oral bacteria to saliva-coated hydroxylapatite in tooth enamel has been found to be inhibited by three milk-derived compounds, namely casein phosphopeptide, sodium caseinate and GMP (glycomacropeptide).
Cheese Cheese has a cariostatic effect by efficiently increasing the concentration of calcium in saliva and plaque. Several studies have demonstrated that cheese consumption, especially aged cheese, after or before exposure to sugary foods prevents a drop in plaque pH and has enamel-protective effects.
Lactoferrin It has been shown that the bovine milk protein, lactoferrin, inhibits the aggregation and adherence of Streptococcus mutans (S. mutans), the main bacteria involved in dental caries, to salivary film.
Probiotics Some studies have shown that probiotics in milk products reduced S. mutans counts, possibly by modifying the composition of salivary film and preventing bacterial adhesion.
Yoghurt There is evidence to indicate that yogurt consumption decreases the number of salivary mutans streptococci as well as lactobacilli, which are often found in dental plaque.
Download Excel Table

The anti-cariogenic effect of dairy products has been attributed to constituents such as calcium, casein and phosphate (Aimutis, 2004). Also bioactive components in milk could reduce dental caries by changing the microbial population of dental plaque, in other words, by inhibition of adhesion of cariogenic streptococcal bacteria and establishment of less cariogenic species such as oral actinomyces (Aimutis, 2004; Johansson and Lif Holgerson, 2011). Animal studies have demonstrated reductions in dental caries when soluble calcium and phosphate salts were added to foods (van der Hoeven, 1985). Epidemiologic studies have shown that children and adults with higher concentrations of calcium and phosphate in their dental plaque had a lower incidence of dental caries (Schamschula et al., 1978). When caseinophosphopeptides from milk react with calcium and phosphate at the tooth surface they produce colloidal amorphous calcium phosphate complexes which promote remineralization of enamel in humans (Aimutis, 2004). In an in vitro study, yoghurt containing casein phosphopeptides prevented demineralization of tooth enamel and enhanced its remineralization (Ferrazzano et al., 2008). A Swedish study found that children who never ate cheese or ate it only once in the five-day period recorded had an average of 1.5 surfaces affected by caries, whereas those who ate cheese five times or more in the five-day period (namely, on average at least once a day) were caries free (Öhlund et al., 2007). A similar study in Japan suggested that high intake of yoghurt may reduce the prevalence of dental caries in children but showed no association between caries and milk or cheese consumption (Tanaka et al., 2010). The exact mechanism by which certain dairy products are anti-cariogenic is still unclear, but the current evidence suggests that consumption of these milk products can protect against dental caries (Johansson and Lif Holgerson, 2011). WHO and FAO (2003) reported that both hard cheese and milk probably decrease risk of dental caries, and that hard cheese also possibly decreases the risk of dental erosion.

Therefore, cow’s milk could be considered non-cariogenic. In vivo and in vitro demineralization and remineralization (enamel slab) experiments also indicated the low cariogenic potential of milk and also demonstrated its caries-protective role. These actions would appear to be due to (i) lactose being the least cariogenic of dietary sugars, (ii) the protective role of casein and possibly fats, and (iii) the protective role of calcium and phosphorus.

Conclusion

Milk and dairy products are healthy foods and considered nutrient-rich because they serve as good sources of calcium and vitamin D as well as protein and other essential nutrients. They provide phosphorus, potassium, magnesium, and vitamins A, B12, and riboflavin. In fact, the calcium in milk and fermented dairy products (yogurt or cheese) could have an important role of supplying calcium or vitamin D each day. And furthermore, getting the recommended three servings of dairy per day can help build bone mass, leading to improved bone health throughout the life cycle. Especially, fermented foods and beverages possess various nutritional and therapeutic properties. Lactic acid bacteria (LAB) play a major role in determining the positive health effects of fermented milks and related products. The calcium in milk is easily absorbed and used in the body, which is why milk and milk products are reliable as well as economical sources of calcium. A diet rich in protein and vitamin D contributes to bone health. Due to their high protein, vitamin D, and calcium content, dairy foods are a good choice for maintaining strong bones. A diet rich in fruit, vegetables and low-fat dairy products, with reduced saturated fat, is as effective as some medications in reducing blood pressure in people with increased blood pressure. It has also been shown to reduce risk of cardiovascular disease and type-2 diabetes. Cultured dairy products such as yogurt contain probiotics which provide a wide array of health benefits. Probiotics in the diet can enhance the good bacteria in the gut, improve health and reduce the risk of certain diseases. For more than 50 years, many studies have consistently provided evidence for the benefits of milk and dairy products on dental health. Milk and dairy products such as cheese and yogurt are beneficial to dental and oral health, and various bioactive peptides found in milk, as well as calcium, have important functions in the maintenance of dental health through enamel-protective and anti-caries effects. Hence, it needs further study the various beneficial interactions between milk & dairy product and human’s health.

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015R1A2A2A01005017).

Disclaimer: The views expressed herein do not necessarily reflect those of the US Food and Drug Administration or the US Department of Health and Human Services.

References

1.

Aimutis, W. R. 2004. Bioactive properties of milk proteins with particular focus on anticariogenesis. J. Nutr. 134(4): 989S-995S .

2.

Bánóczy, J., Petersen, P. E. and Rugg-Gunn, A. J. 2009. Milk fluoridation for the prevention of dental caries. World Health Organization .

3.

Baran, D., Sorensen, A., Grimes, J., Lew, R., Karellas, A., Johnson, B. and Roche, J. 1990. Dietary modification with dairy products for preventing vertebral bone loss in premenopausal women: A three year prospective study. J. Clin. Endocr. Metab. 70(1):264-270 .

4.

Bonjour, J. P., Chevalley, T., Ammann, P., Slosman, D. and Rizzoli, R. 2001. Gain in bone mineral mass in prepubertal girls 3-5 years after discontinuation of calcium supplementation: a follow-up study. Lancet 358:1208-1212 .

5.

Braun, M., Palacios, C., Wigertz, K., Jackman, L. A., Bryant, R. J., McCabe, L. D., Martin, B. R., McCabe, G. P., Peacock, M. and Weaver, C. M. 2007. Racial differences in skeletal calcium retention in adolescent girls on a range of controlled calcium intakes. Am. J. Clin. Nutr. 85:1657-1663 .

6.

Buchanan, D. S. 2002. Dairy animals: Major Bos taurus breeds. In H. Roginski, J. W. Fuquay & P. F. Fox, eds. Encyclopedia of dairy sciences, Vol. 2, pp. 559-568. London, Academic Press, London .

7.

Cheng, S., Lyytikainen, A., Kroger, H., Lamberg-Allardt, C., Alen, M., Koistinen, A., Wang, Q. J., Suuriniemi, M., Suominen, H., Mahonen, A., Nicholson, P. H., Ivaska, K. K., Korpela, R., Ohlson, C., Vaananen, K. H. and Tylavasky, F. 2005. Effects of calcium, dairy product, and vitamin D supplementation on bone mass accrual and body composition in 10-12 y-old girls: A 2-y randomized trial. Am. J. Clin. Nutr. 82:1115-1126 .

8.

Clare, D. A., Catignani, G. L. and Swaisgood, H. E. 2003. Biodefense properties of milk: The role of antimicrobial proteins and peptides. Curr. Pharm. Des. 9:1239-1255 .

9.

Daniel, H., Vohwinkel, M. and Rehner, G., 1990. Effect of casein and beta-casomorphins on gastrointestinal motility in rats. J. Nutr. 3:252-257 .

10.

Donovan, S. M. 2006. Role of human milk components in gastrointestinal development: Current knowledge and future needs. J. Pediatr. 149:49-61 .

11.

Doreau, M. and Martin-Rosset, W. 2002. Dairy animals. Horse. In R. Hubert, ed. Encyclopedia of dairy sciences, pp. 630-637. London, Academic Press .

12.

Dunshea, F. R., Ostrowska, E., Ferrari, J. M. and Gill, H. S. 2007. Dairy proteins and the regulation of satiety and obesity. Austral. J. Exper. Agric. 47:1051-1058 .

13.

Ebringer, L., Ferencik, M. and Krajcovica, J. 2008. Beneficial health effects of milk and fermented dairy products. Folia Microbiol. 53:378-394 .

14.

Ebringer, L., Ferencik, M. and Krajcovica, J. 2008. Beneficial health effects of milk and fermented dairy products. Folia Microbiol. 53:378-394 .

15.

Elders, P. J. M., Lips, P., Netelenbos, J. C., van Ginkel, F. C., Khoe, E., van der Vijgh, W. J. F. and van der Stelt, P. F. 1994. Long-term effect of calcium supplementation on bone loss in perimenopausal women. J. Bone Miner. Res. 9:963-970 .

16.

EUFIC. 1999. It's a tiny world. Food Today No. 16. Brussels, European Food Information Council. Available at: http:// www.eufic.org/article/en/page/FTARCHIVE/artid/microbes-micro-organisms/. Accessed 5 February 2016 .

17.

FAO & WHO. 2009. Code of hygienic practice for milk and milk products. Codex Alimentarius. CAC/RCP 57- 2004. Available at: http://www.codexalimentarius.org/ download/standards/10087/CXP_057e.pdf. Accessed 18 March 2016 .

18.

FAO. 2003. The yak (2nd ed.). Revised and enlarged by G. Wiener, H. Jianlin and L. Ruijun. RAP publication 2003/6 Bangkok, FAO Regional Office for Asia and the Pacific (RAP). Available at: http://www.fao.org/docrep/ 006/ad347e/ad347e00.htm. Accessed 21 January 2016 .

19.

FAO. 2008. Milk and dairy products [web page]. Animal Production and Health Division, FAO, Rome. Available at: http://www.fao.org/ag/againfo/themes/en/dairy/home. html. Accessed 23 January, 2016 .

20.

FAOSTAT. 2012. FAO statistical database. Available at: http://faostat.fao.org/. Accessed 21 February 2016 .

21.

Ferrazzano, G. F., Cantile, T., Quarto, M., Ingenito, A., Chianese, L. and Addeo, F. 2008 Protective effect of yoghurt extract on dental enamel demineralization in vitro. Aus. Dent. J. 53(4):314-319 .

22.

FitzGerald, R. J. and Meisel, H. 2003. Milk protein hydrolysates and bioactive peptides. Adv. Dairy Chem. 3: 675-698 .

23.

Fox, P. F. 2008. Milk: an overview. In A. Thompson, M. Boland & H. Singh, eds. Milk proteins: from expression to food, pp. 1-54. San Diego, CA, USA, Academic Press .

24.

Hill, K., Braun, M. M., Kern, M., Martin, B. R., Navalta, J., Sedlock, D., McCabe, L. D., McCabe, G. P., Peacock, M. and Weaver, C. M. 2008. Predictors of calcium retention in adolescent boys. J. Clin. Endocr. Metab. 93(12): 4743-4748 .

25.

Huncharek, M., Muscat, J. and Kupelnick, B. 2008. Impact of dairy products and dietary calcium on bone-mineral content in children: results of a meta-analysis. Bone 43: 312-321 .

26.

Jenkins, G. N. and Ferguson, D. B. 1966. Milk and dental caries. Brit. Dent. J. 120(10):472-477 .

27.

Johansson, I. and Lif Holgerson, P. 2011. Milk and oral health. In R. A. Clemens, O. Hernell, K. F. Michaelsen, eds. Milk and milk products in human nutrition, pp. 55-66. Basel, Switzerland, S. Karger AG; Vevey, Switzerland, Nestle Nutrition Institute .

28.

Kerstetter, J. E. 1995. Do dairy products improve bone density in adolescent girls? Nutr. Rev. 53:328-332 .

29.

Kitts, D. D. and Weiler, K., 2003. Bioactive proteins and peptides from food sources. Applications of bioprocesses used in isolation and recovery. Curr. Pharm. Des. 9:1309- 1323 .

30.

Korhonen, H. and Pihlanto, A. 2003. Food-derived bioactive peptides opportunities for designing future foods. Curr. Pharm. Des. 9:1297-1308 .

31.

Lempert, S. M., Christensen, L. B., Froberg, K., Raymond, K. and Heitmann, B. L. 2015. Association between dairy intake and caries among children and adolescents, results from the Danish EYHS follow-up study. Caries. Res. 49:251-258 .

32.

MacDonald, H. B. 2000. Conjugated linoleic acid and disease prevention: A review of current knowledge. J. Am. Colleg Nutr. 19:111-118 .

33.

Matkovic, V., Goel, P. K., Badenkop-Stevens, N. E., Landoll, J. D., Li, B., Ilich, J. Z., Skugor, M., Nagode, L. A., Mobley, S. L., Ha, E-J., Hangartner, T. N. and Clairmont, A. 2005. Calcium supplementation and bone mineral density in females from childhood to young adulthood: A randomized controlled trial. Am. J. Clin. Nutr. 81:175-188 .

34.

McBean, L. D. 1999. Emerging dietary benefits of dairy foods. Nutr. 34:47-53 .

35.

McIntosh, G. H., Royle, P. J., LeLeu, R. K., Regester, G. O., Johnson, M. A., Grinsted, R. L., Kenward, R. S. and Smithers, G. W. 1998. Whey proteins as functional food ingredients. Int. Dairy J. 8:425-434 .

36.

Meisel, H. and Bockelmann, W. 1999. Bioactive peptides encrypted in milk proteins: Proteolytic activation and thropho-functional properties. Antonie Van Leeuwenhoek 76:207-215 .

37.

Meisel, H. and FitzGerald, R. J. 2003. Biofunctional peptides from milk proteins: Mineral binding and cytomodulatory effects. Curr. Pharm. Des. 9:1289-1295 .

38.

Merritt, J., Qi, F. and Shi, W. 2006. Milk helps build strong teeth and promotes oral health. J. Calif. Dent. Assoc. 34:361-366 .

39.

Metschnikoff, E. 1907. The prolongation of life. Optimistic studies (London, UK, William Heinemann) .

40.

New, S. A., Bolton-Smith, C., Grubb, D. A., and Reid, D. M. 1997. Nutritional influences on bone mineral density: A cross-sectional study in premenopausal women. Am. J. Clin. Nutr. 65:1831-1839 .

41.

Nordin, B. E. C., Polley, K. J., Need, A. G., Morris, H. A., and Marshall, D. 1987. The problem of calcium requirement. Am. J. Clin. Nutr. 45:1295-1304 .

42.

Öhlund, I., Holgerson, P. L., Bäckman, B., Lind, T., Hernell, O. and Johansson, I. 2007. Diet intake and caries prevalence in four-year-old children living in a low prevalence country. Caries Res. 41(1):26-33 .

43.

Parvez, S., Malik, K. A., Kang, S. A. and Kim, H. Y. 2006. Probiotics and their fermented food products are beneficial for health. J. Appl. Microbiol. 100:1171-1185 .

44.

Rafferty, K. and Heaney, R. P. 2008. Nutrient effects on the calcium economy: Emphasizing the potassium controversy. J. Nutr. 138:166S-171S .

45.

Rautava, S., Kalliomaki, M. and Isolauri, E. 2002. Probiotics during pregnancy and breast-feeding might confer immunomodulatory protection against atopic disease in the infant. J. Allergy Clin. Immunol. 109:119-121 .

46.

Recker, R. R. and Heaney, R. P. 1985. The effect of milk supplements on calcium metabolism, bone metabolism, and calcium balance. Am. J. Clin. Nutr. 41:254-263 .

47.

Rogelj, I. 2000. Milk, dairy products, nutrition and health. Food Technol. Biotechnol. 38:143-147 .

48.

Saito, T., Nakamura, T., Kitazawa, H., Kawai, Y. and Itoh, T. 2000. Isolation and structural analysis of antihypertensive peptides that exist naturally in Gouda cheese. J. Dairy Sci. 83:1434-1440 .

49.

Santosa, S., Farnworth, E. and Jones, P. J. 2006. Probiotics and their potential health claims. Nutr. Rev. 64:265-274 .

50.

Schamschula, R. G., Bunzel, M., Agus, H. M., Adkins, B. L., Barmes, D. E. and Charlton, G. 1978. Plaque minerals and caries experience: Associations and interrelationships. J. Dent. Res. 57(3):427-432 .

51.

Shah, N. P. 2007. Functional cultures and health benefits. Int. J. Dairy. 17:1262-1277 .

52.

Shaw, J. H., Ensfied, B. J. and Wollman, D. H. 1959. Studies on the relation of dairy products to dental caries in caries-susceptible rats. J. Nutr. 67(2):253-273 .

53.

Shortt, C., Shawand, D. and Mazza, G. 2004. Overview of opportunities for health-enhancing functional dairy products. In Handbook of functional dairy products. Shortt C. and J. O'Brien. (Ed.). New York, U. S. A: CRC Press, 1-12 .

54.

Tanaka, K., Miyake, Y. and Sasaki, S. 2010. Intake of dairy products and the prevalence of dental caries in young children. J. Dent. 38(7):579-583 .

55.

Tannock, G. W. 2002. Probiotics and prebiotics. Where are we going?. Norfolk, UK: Caister Acad Press .

56.

Teegarden, D., Legowski, P., Gunther, C. W., McCabe, G. P., Peacock, M. and Lyle, R. M. 2005. Dietary calcium intake protects women consuming oral contraceptives from spine and hip bone loss. J. Clin. Endocr. Metab. 90: 5127-5133 .

57.

Theobald, H. E. 2005. Dietary calcium and health. Brit. J. Nutr. 30:237-277 .

58.

Tu, M.-Y., Chen, H.-L., Tung, Y.-T., Kao, C.-C., Hu, F.-C. and Chen, C.-M. 2015. Short-term effects of kefir-fermented milk consumption on bone mineral density and bone metabolism in a randomized clinical trial of osteoporotic patients. PLoS ONE 10(12):e0144231. doi:10.1371/journal. pone.0144231 .

59.

USDA and USDHHS. 2010. Dietary guidelines for Americans, 2010. 7th Edition. Washington, DC, US Government Printing Office. Available at: http://www.cnpp.usda.gov/ Publications/DietaryGuidelines/2010/PolicyDoc/PolicyDoc.pdf. Accessed 1 April 2016 .

60.

USDHHS and USDA. 2005. Dietary guidelines for Americans, 2005. 6th Edition.Washington, DC, US Government Printing Office. Available at: http://www.health.gov/dietary guidelines/dga2005/document/pdf/DGA2005.pdf. Accessed 30 March 2016 .

61.

USDHHS. 2000. Oral health in America: A report of the Surgeon General. Rockville, MD, USA. United States Department of Health and Human Services, National Institute of Dental and Craniofacial Research, National Institutes of Health .

62.

van der Hoeven, J. S. 1985. Effect of calcium lactate and calcium lactophosphate on caries activity in programme- fed rats. Caries Res. 19(4):368-370 .

63.

Weaver, C. M. 2008. Osteoporosis: the early years. In A. M. Coulston & C. J. Boushey, eds. Nutrition in the prevention and treatment of disease, 2nd Ed., pp. 833-851. San Diego, CA, USA, Academic Press .

64.

Weaver, C. M., Proulx, W. R. and Heaney, R. P. 1999. Choices for achieving dietary calcium within a vegetarian diet. Am. J. Clin. Nutr. 70:543S-548S .

65.

Weinsier, R. L. and Krumdieck, C. L. 2000. Dairy foods and bone health: examination of the evidence. Am. J. Clin. Nutr. 72:681-689 .

66.

Welten, D. C., Kemper, H. C., Post, G. B. and van Staveren, W. A. 1995. A meta-analysis of the effect of calcium intake on bone mass in young and middle aged females and males. J. Nutr. 125:2802-2813 .

67.

WHO & FAO. 2003. Diet, nutrition and the prevention of chronic diseases. Report of a Joint WHO/FAO Expert Consultation. WHO Technical Report Series 916. Geneva, World Health Organization .

68.

WHO, FAO & UNU. 2007. Protein and amino acid requirements in human nutrition. Report of a Joint WHO, FAO and UNU Expert Consultation, WHO Technical Report Series 935. Available at: hqlibdoc.who.int/trs/WHO_TRS_ 935_eng.pdf. Accessed 12 January 2016 .