Nutrition Publication

NNIW67 - Milk and Milk Products in Human Nutrition

Editor(s): R.A. Clemens, O. Hernell, K.F. Michaelsen. vol. 67

Milk plays a major role in a healthy, balanced diet throughout lifetime. Initially, human milk is the sole source of nutrition in early infancy and milk substitutes have to be chosen carefully as they should be suitable for the infant and deliver as close as possible the health benefits that human milk provides to the infant. During the weaning period milk remains an important part of the diet in completing the nutritional requirements, e.g. for protein, minerals etc. Milk continues to deliver benefits in children of school age throughout adolescence and adult life with regard to bone and heart health and others.

Related Articles

Milk Intake, Calcium and Vitamin D in Pregnancy and Lactation: Effects on Maternal, Fetal and Infant Bone in Low- and High-Income Countries

Author(s): A. Prentice

Calcium and vitamin D are essential for bone growth and maintenance. Among the bone-forming minerals, dietary calcium supply is close to biological requirements and may be limiting in some parts of the world where there are few rich dietary sources of calcium, particularly for children, and women during pregnancy and lactation. Animal milk is a rich source of calcium and, in countries where milk is fortified with vitamin D, a contributor to dietary vitamin D intake. Current evidence indicates that, in the human, there are physiological mechanisms that support the necessary calcium fluxes across the placenta and mammary gland and that are unresponsive to increases in calcium intake. This applies across the range of dietary calcium intakes recorded in healthy individuals. In contrast, although there is unlikely to be an additional requirement for vitamin D during pregnancy and lactation, many women have poor vitamin D status. This places them at risk of osteomalacia and their infants at risk of rickets, osteomalacia, compromised skeletal growth and other outcomes. There needs to be increased awareness among policy-makers, health professionals and the public about the importance of safe UVB sunshine exposure and consumption of dietary vitamin D by women of reproductive age at risk of vitamin D deficiency.

Human Milk vs. Cow’s Milk and the Evolution of Infant Formulas

Author(s): O. Hernell

Until the early 20th century a wet nurse was the only safe alternative to breastfeeding, one reason being that each species has a unique composition of its milk. When techniques for chemical analyses of milks and assessment of the energy requirements of infants became available during the 19th century reasonably safe breast milk substitutes started to be developed. Successively these were developed into modern infant formulas during the 20th century using human milk composition as reference and cow´s milk as protein source. Even with a composition similar to human milk there are differences in performance between formula-fed and breastfed infants. Novel ingredients and new techniques within the dairy industry will contribute to minimize these differences and so might techniques in molecular biology allowing large scale production of recombinant human milk proteins. This technique may be used for production of bioactive substances present in low concentrations in human milk but absent from bovine milk with proven effect on nutrient utilization or other health benefits. For formulas containing novel ingredients with potent biological activities produced with new techniques it will be extremely important that their safety and efficacy are rigorously evaluated because "functional effects" are not necessarily the same as health benefits.

Whole Cow's Milk in Early Life

Author(s): I. Thorsdottir, A.V. Thorisdottir

Cow's milk is major food for young children. During infancy whole cow’s milk is known for negative effects mainly on iron status. The negative association to iron status led to the recommendation to introduce formula feeding in infancy during the weaning period or when breastfeeding ceased. More recently the literature suggests unfortunate effects of whole cow's milk in infancy on growth, especially weight acceleration and association with the development of overweight in childhood. These issues are discussed in the following chapter. Other suggested reasons for the avoidance of whole cow's milk in infancy are touched upon, as milk protein allergy and high renal solute load. The hypothesis about early cow’s milk introduction in the pathology of certain diseases, mainly through the peptide beta-casomorphin-7, is shortly reviewed showing no clear evidence for the suggested associations. The chapter gives a recent example on an introduction of formula at six months of age instead of whole cow’s milk in infants' diet in Iceland. Several aspects on the consumption of whole cow's milk in infancy can better be found in recent reviews as for example the disussion on fat quality and quantity.

Biological Effects of Novel Bovine Milk Fractions

Author(s): B. Lönnerdal

Novel dairy fractions have been isolated and are now commercially available. Several of them have been shown to have biological activities in various test systems.α-Lactalbumin was first isolated to provide a good source of tryptophan, often the first limiting amino acid in infant formulas, but has then been shown to be digested into smaller peptides with antimicrobial and prebiotic activities, immunostimulatory effect and acting as enhancers of mineral absorption. Lactoferrin bioactivities include anti-bacterial and antiviral effects, regulation of immune function, stimulation of intestinal proliferation and differentiation and facilitating iron absorption, but these activities may have been limited due to earlier contamination with lipopolysaccharide (LPS). Lactoferrin free of LPS may prove to be more effective with regard to exerting these activities. Osteopontin is a heavily phosphorylated and glycosylated protein that modulates immune function and stimulates Th1/Th2 switching, and, possibly, also affects bone mineralization and growth. Biological activities of lactoferrin may be facilitated by osteopontin. Milk fat globule membranes is a fraction that has previously been excluded from infant formulas, but components of this fraction has been shown to exhibit antimicrobial activities and to prevent infection. Further clinical studies are needed on infants fed formulas with these components incorporated.

Milk and Oral Health

Author(s): I. Johansson

Oral health includes freedom from disease in the gums, the mucosa and the teeth. Dental caries and periodontitis, if left untreated, may lead to pain and may impair quality of life, and nutritional status. Oral health inequality is a serious reality both within industrialized countries and between industrialized countries and less developed countries. To overcome this, a multidimensional approach must be taken. The basis will be the traditional preventive measures that have proven successful, but newer cost-effective prevention/treatment strategies must be applied. Non-sweetened dairy products or specific bioactive components from alike sources might prove to be part of such strategies. However, properly designed clinical studies in target groups are needed. That kind of studies must include the effects of confounders and involve caries in various risk groups and types of disease, such as children and underprivileged groups in general, orthodontic patients, dry mouth groups, coronary and root caries conditions to overcome the shortcomings of the present studies.

Milk and Growth in Children: The Effects of Whey and Casein

Author(s): C. Mølgaard, A. Larnkjær, K. Arnberg, K.F. Michaelsen

Consumption of cow’s milk is recommended in many countries. Observational and intervention studies show that cow’s milk most likely has a positive influence on growth in children. The strongest evidence come from observational studies and intervention studies in low income countries, but there are also observational studies from high income countries showing positive associations between milk intake and growth. Milk seems thus to have a specific stimulating effect on linear growth, not only in developing countries with high rates of malnutrition, but also in industrialised countries. However, it is not known which components in milk stimulate growth. Possible components are proteins, minerals, vitamins or combinations of these. Cow’s milk proteins have a high protein quality and whey has a slightly higher quality than casein, according to some indices based on amino acid composition. Studies, mainly from sport medicine, have suggested that whey protein also has the potential to increase muscle mass. Whether whey improves body composition to a larger extent than other milk proteins is not clear. The mechanism behind a possible growth stimulating effect of milk and milk components is likely to be through a stimulation of IGF-I synthesis and maybe insulin secretion. In conclusion, there is strong evidence that milk stimulates linear growth. The mechanism is not yet clear and more intervention studies are needed to understand which components in milk are responsible for the growth stimulation. The effects of milk on linear growth and adult height may have both positive and negative long term implications.

Milk and Linear Growth: Programming of the IGF-1 Axis and Implication for Health in Adulthood

Author(s): R.M. Martin, J.M.P. Holly, D. Gunnell

There is increasing awareness that childhood circumstances influence disease risk in adulthood. As well as being strongly influenced by genes / genetic factors, stature acts as a marker for early-life exposures, such as diet, and is associated with risk of several chronic diseases in adulthood. Stature is also a marker for levels of insulin-like growth factor (IGF)-I in childhood. Levels of IGF-I are nutritionally regulated and are therefore modifiable. Milk intake in childhood and in adulthood is positively associated with higher levels of circulating IGF-I and, in children, higher circulating IGF-I promotes linear growth. Studies conducted by our team and others, however, indicate that the effect of milk is complicated because consumption in childhood appears to have long-term, programming effects which are opposite to the immediate effects of consuming milk. Specifically, studies suggest that the long-term effect of higher levels of milk intake in early childhood is opposite to the expected short-term effect, because milk intake in early-life is inversely associated with IGF-I levels throughout adult life. We hypothesise that this long-term programming effect is via a resetting of pituitary control in response to raised levels of IGF-I in childhood. Such a programming effect of milk intake in early life could potentially have implications for cancer and ischaemic heart disease risk many years later.

Milk in Treatment of Moderate and Severe Undernutrition in Low-Income Countries

Author(s): K.F. Michaelsen, A-L.H. Nielsen, N. Roos, H. Friis, C. Mølgaard

Cow’s milk products have a central role in treatment of undernutrition and the introduction of products with a high milk content (F-100 and RUTF) have resulted in marked improvements in weight gain and reduction in mortality. Milk also has a specific effect on linear growth. Milk protein has a high quality score (PDCAAS) and contains many peptides and other bio-active factors, which might have special effects on recovery from undernutrition. Milk is an important source of minerals supporting growth (type II nutrients), such as potassium, magnesium, phosphorus and zinc and the high lactose content also seems to support growth due to a prebiotic effect and improved absorption of minerals. The risk that the use of cow’s milk products suppresses breastfeeding should be prevented by supporting mothers in breastfeeding. There is consensus that children with severe undernutrition should be treated with products with high milk content but because of the high cost of milk there is a need to perform more studies to determine the minimal amount of milk protein needed to make a clinically relevant difference in treating the 36 million children with moderate wasting. Such studies should not only focus on weight gain but also on linear growth, body composition, physical activity and cognitive development.

Effects of Animal Source Foods, with Emphasis on Milk, in the Diet of Children in Low-Income Countries

Author(s): L.H. Allen, D.K. Dror

This review evaluates evidence for benefits of including animal source foods (ASF) in the diets of children in developing countries. In observational studies, a higher usual intake of ASF in such countries is associated with better growth, status of some micronutrients, cognitive performance, motor development and activity. Only three randomized trials supplemented children with milk and compared outcomes to a non-intervention control group. Both height and weight growth were improved, although in Kenya height was increased only in younger schoolers who were stunted at baseline. Meat supplements have been evaluated in only two randomized controlled trials, in Kenya and Guatemala (mean baseline age 8 years and 1 year respectively); growth was no better than in an equi-caloric control group. Meat improved cognitive function and activity in Kenya; milk was less effective than meat for improving cognitive function and physical activity, perhaps due to its lower content of iron, zinc, or riboflavin. Meat and especially cow’s milk are excellent sources of vitamin B12, a micronutrient commonly deficient in populations which consume low amounts of ASF. Other micronutrients such as iron have been added to cow’s milk and resulted in improved nutritional outcomes for children.

Evidence for Acne-Promoting Effects of Milk and Other Insulinotropic Dairy Products

Author(s): B.C. Melnik

Acne vulgaris, the most common skin disease of Western civilization, has evolved to an epidemic affecting more than 85% of adolescents. Acne can be regarded as an indicator disease of exaggerated insulinotropic Western nutrition. Especially milk and whey protein-based products contribute to elevations of postprandial insulin and basal IGF-1 plasma levels. It is the evolutional principle of mammalian milk to promote growth and support anabolic conditions for the neonate during the nursing period. Whey proteins are most potent inducers of glucose-dependent insulinotropic polypeptide secreted by enteroendocrine K-cells which in concert with hydrolyzed whey protein-derived essential amino acids stimulate insulin secretion of pancreatic β-cells. Increased insulin/IGF-1 signaling activates the phosphoinositide-3 kinase (PI3K)/Akt pathway thereby reducing the nuclear content of the transcription factor FoxO1, the key nutrigenomic regulator of acne target genes. Nuclear FoxO1 deficiency has been linked to all major factors of acne pathogenesis, i.e., androgen receptor transactivation, comedogenesis, increased sebaceous lipogenesis, and follicular inflammation. The elimination of the whey protein-based insulinotropic mechanisms of milk will be the most important future challenge for nutrition research. Both, restriction of milk consumption or generation of less insulinotropic milk will have an enormous impact on the prevention of epidemic Western diseases like obesity, diabetes mellitus, cancer, neurodegenerative diseases and acne.

Milk Proteins in the Regulation of Bodyweight, Satiety, Food Intake and Glycemia

Author(s): G.H. Anderson, B. Luhovyy, T. Akhavan, S. Panahi

Consumption of dairy products and their milk proteins increase satiety and reduce food intake and blood glucose response when consumed alone or with carbohydrate. Dairy proteins are of interest because proteins are more satiating than either carbohydrate or fat and they regulate food intake and metabolic functions by the combined actions of the intact protein, encrypted peptides and amino acids on gastrointestinal and central pathways. As shown in this review, milk proteins have physiologic functions that contribute to the maintenance of a health body weight and control of factors associated with the metabolic syndrome through 2 their effects on mechanisms regulating food intake and blood glucose. More recent reports show that these benefits can be achieved within the range of usual consumption of dairy. In addition, recent research points to an intrinsic value of small amounts of milk protein or dairy consumed shortly before a meal to reduce the glycemic response to carbohydrate and that this is not at the cost of increased demand for insulin.

Lactose Intolerance: An Unnecessary Risk for Low Bone Density

Author(s): D. Savaiano

The potential for lactose intolerance causes 25 to 50 million Americans to avoid milk. Milk avoidance is a significant risk factor for low bone density. Individuals who avoid milk, due to intolerance or learned aversion, consume significantly less calcium and have poorer bone health and probable higher risk of osteoporosis. Lactose intolerance is easily managed by: 1) regular consumption of milk that adapts the colon bacteria and facilitate digestion of lactose 2) consumption of yogurts and cheeses and other dairy foods low in lactose 3) consumption of dairy foods with meals to slow transit and maximize digestion and 4) use of lactose digestive aids. As dairying spreads around the world to new markets and dairy foods become the dominant source of calcium in these markets, the potential for lactose intolerance will grow. Management of lactose intolerance globally will require both education and product development.

Milk and the Risk and Progression of Cancer

Author(s): C.L. Rock

Observational evidence suggests that nutritional factors contribute to a substantial proportion of cancer cases, and milk contains numerous bioactive substances that could affect risk and progression of cancer. Cancer results from multiple genetic and epigenetic events over time, so demonstrating a specific effect of nutrients or other bioactive food components in human cancer is challenging. Epidemiological evidence consistently suggests that milk intake is protective against colorectal cancer. Calcium supplements have been shown to reduce risk for recurrence of adenomatous polyps. Calcium supplementation has not been observed to reduce risk for colon cancer, although long latency and baseline calcium intake affect interpretation of these results. High calcium intake from both food and supplements is associated with increased risk for advanced or fatal prostate cancer. Results from epidemiological studies examining the relationship between intake of dairy foods and breast or ovarian cancer risk are not consistent. Animal studies have suggested that galactose may be toxic to ovarian cells, but results from epidemiological studies that have examined ovarian cancer risk and milk and/or lactose intakes are mixed. Dietary guidelines for cancer prevention encourage meeting recommended levels of calcium intake primarily through food choices rather than supplements, and choosing low-fat or nonfat dairy foods.

Milk A1 and A2 Peptides and Diabetes

Author(s): R. A. Clemens

Food-derived peptides, specifically those derived from milk, may adversely affect health by increasing the risk of insulin-dependent diabetes. This position is based on the relationship of Type 1 diabetes (T1D) and the consumption of variants A1 and B β-casein from cow milk. It appears that β-casomorphin (BCM-7) from β-casein may function as an immunosuppressant and impair tolerance to dietary antigens in the gut immune system, which, in turn, may contribute to the onset of T1D. There are 13 genetic variants of β-casein in dairy cattle. Among those variants are A1, A2, and B, which are also found in human milk. The amino acid sequences of β-casomorphins among these bovine variants and those found in human milk are similar, often differing only by a single amino acid. In vitro studies indicate BCM-7 can be produced from A1 and B during typical digestive processes; however, BCM-7 is not a product of A2 digestion. Evidence from several epidemiological studies and animal models does not support the association of milk proteins, even proteins in breast milk, and the development of T1D. Ecological data, primarily based on A1/A2 variations among livestock breeds, do not demonstrate causation, even among countries where there is considerable dairy consumption.

Milk Fat and Health Consequences

Author(s): R.A. Gibson

Dairy foods are widely recommended as part of a healthy diet mainly because of the ready availability of calcium but also because they are a good source of protein, minerals and fat soluble vitamins.On the other hand, dairy foods have been viewed with suspicion by many because dairy fats contain saturated fatty acids and cholesterol.It has been thought, particularly by consumers, that dairy fats may increase the risk of coronary heart disease because of the contribution they make to total saturated fat intake.However, dairy fats contain other lipid bioactives (e.g. omega-3 fatty acids, gangliosides, conjugated linoleic acid) that may counteract the effect of saturates in a well balanced diet. Surprisingly, there have been few studies that have addressed this issue.