Health & Wellness Milk Muscle Gain

Milk: Not a simple nutrient but a signaling system for growth

the health benefits of drinking milk

MILK is the primary source of nutrition for infant mammals and is produced by the mammary glands. The sugar in milk is called lactose and it requires a chemical or enzyme called lactase to allow it to pass across the walls of the gut into the blood stream. Milk, and other dairy foods, provide the best source of dietary calcium and contain protein, vitamin A, vitamin B 12, magnesium, phosphorus, potassium, riboflavin and zinc [1]. It is considered to be the only foodstuff that contains all substances known to be essential for human nutrition.

Fun fact: In the past, the average cow produced around 600 kg of milk per lactation period. Nowadays it may reach 6,000–8,000 kg. Today, world production is estimated at over 700 million tons and increasing rapidly [2].

Nutritional facts (whole fat) [3]:
  • Water 88.32 g
  • Carbohydrate (as Lactose) 4.52 g
  • Fat 3.25 g
  • Protein 3.22 g
Vitamins
  • Vitamin A 28 µg
  • Thiamin (Vitamin B1) 0,044 mg
  • Riboflavin (Vitamin B2) 0,183 mg
  • Niacin (Vitamin B3) 0.107 mg
  • Pantothenic Acid (Vitamin B5) 0.362 mg
  • Vitamin B6 (Pyridoxine) 0.036 mg
  • Vitamin B12 (Cobalamin) 0.44 µg
  • Vitamin D 40 IU
  • Vitamin E 0,06 mg
  • Folate 5 µg
  • Vitamin K 0,2 µg
Minerals
  • Calcium 113 mg
  • Copper 0.011 mg
  • Iron 0.03 mg
  • Magnesium 10 mg
  • Phosphorus 91 mg
  • Potassium 143 mg
  • Selenium 3,7 µg
  • Sodium 40 mg
  • Zinc 0,4 mg
Recommended dose

The Cancer Council, USDA and Australian Dietary Guidelines all recommend 3 servings of milk and milk products daily. While Canada’s Food Guide recommends that all Canadians should consume from 2 to 4 servings of milk and milk products daily. One serving of milk equals to 250 ml or 1 cup.

Calcium

Calcium is a major component of bones and teeth. It also is required for the clotting of blood to stop bleeding and for normal functioning of the nerves, muscles, and heart [4]. The mechanism by which calcium intake affects bone health is by increasing bone mineral density (BMD). Results of observational and intervention studies in relation to calcium and dairy food consumption have been inconsistent and are mainly attributed to the different sex and age-stages, the effect of hormonal changes, reliance on recalled data, and the limitations of assessment methods [5]. Nevertheless, milk seems to be the main factor for optimal bone health as it is the primary source of calcium in the diets of adolescents and children [6,7]. Besides calcium, milk also provides phosphates, magnesium, and proteins, which are likely to be associated with BMD [6,7]. A 2008 meta-analysis [8] concluded that increased dietary calcium/dairy products (with and without vitamin D) significantly increases total body and lumbar spine bone mineral content in children with low base-line intakes. They also noted that current dietary calcium recommendations for children and adolescents appear justified. In growing children, avoiding of cow milk is associated with smaller height, higher BMI and poor bone health (smaller bones, lower total-body bone area, a lower total-body bone mineral content) [9].

1 serving of milk glassIn adult population milk consumption has been reported to reduce bone turnover by about 20% which leads to small observed increase in BMD [11]. Meta-analysis by Tai, et al. [10] concluded that increasing calcium intake either by dietary sources or supplements has small non-progressive effects on bone density.

Calcium content in milk (250 ml) [1]:

  • Full cream milk 285 mg
  • Skim milk 310 mg

Fracture Risk

There is evidence to suggest that peak bone mass and later fracture risk are influenced by the pattern of growth in childhood and by nutritional exposures in utero, in infancy and during childhood and adolescence (especially Ca, vitamin D, protein and P) [7]. In children, an association between low bone density and fractures is reported [13]. In a study [9], evaluating 50 children who avoided cow’s milk (30 girls, 20 boys) aged 3–10 years, a relatively high proportion had already experienced broken bones. Twelve subjects, of whom 6 were overweight, reported 17 previous fractures.

In adults, numerous cohort studies assessed the relation between dietary calcium, milk or dairy intake, and risk of fracture, and most reported neutral associations [12]. In a systematic review of calcium intake and fractures, it was concluded that there is no evidence of an association between increased dietary calcium intake and lower risk of fracture [12]. Meta-analysis by Tai and associates [10] reported that observed small non-progressive increase in bone density is unlikely to translate into reductions in fractures. A review of cohort studies [15] reported that milk consumption dose-dependently increased the rate of fracture in women but not in men. Interestingly, this pattern was not observed with high intake of fermented milk products (yogurt, soured milk, …).

At this time, it is not possible to define dietary reference values using bone health and the question about what type of diet is the best for optimal bone growth and development remains open. Evidence that calcium intake prevent fractures is weak and inconsistent.

Lactose and D-galactose

Lactose is a disaccharide sugar made of galactose and glucose. Typically all milks contain approximately 5.0% lactose by weight [14]. In order for humans to digest lactose we need the enzyme called lactase (β-D-galactosidase) to digest it.

In humans, milk is the primary source of D-galactose, which may have undesirable effects. Michaëlsson and colleagues [15] suggest that milk is harmful because of D-galactose, as it mimics aging through inflammation and oxidative stress in animal models [21]. D-galactose is even used as an aging model in animal studies and findings suggest that chronic D-galactose exposure causes neurodegeneration [22]. Human studies also confirm that milk, but not fermented dairy products, is positively associated with a biomarker of oxidative stress [15].

Milk and All-Cause Mortality Risk

Based on observational evidence, Michaëlsson and colleagues raise the possibility that milk could increase cardiovascular and overall mortality in men and women [15]. Dik et al. [18] also observed a positive association between high consumption of milk and all-cause mortality in a pooled analysis of cohort studies from 10 European countries. However, prospective observational evidence available does not consistently show higher milk intake to be associated with cardiovascular mortality, or death [17,19,20]. These findings should be interpreted with caution as these reviews rely on observational and not experimental evidence, which may potentially reflect correlation not causation.

An interesting recent small randomized cross over study indicated that the intake of a fermented dairy diet seemed to provide a more favourable biomarker profile than that of a non-fermented dairy diet [23].

As professor Mary Schooling said [16] :”… the role of milk in mortality needs to be established definitively now.

Steroid Hormones, Growth Factors and Contaminants in Cow’s Milk

Milk is a valuable nutrient source for humans, but recent reports have questioned its safety because of the presence of steroid hormones in milk. There is growing concern of whether or not exposure to the estrogens from milk can cause adverse effects in the consumer. Modern genetically improved dairy cows continue to lactate throughout almost the entire pregnancy. It is known that steroid hormones pass the blood-milk barrier [24]. Therefore, recent commercial cow’s milk contains large amounts of estrogens and progesterone [25] and also biologically significant levels of insulin-like growth factor-I (IGF-I) and recombinant bovine growth hormone (rbGH) [26].

In mammals, chemicals having estrogenic activity can produce many health-related problems, such as early puberty in females, reduced sperm counts, altered functions of reproductive organs, obesity, and altered sex-specific behaviors [27]. Fetal, newborn, and juvenile mammals are especially sensitive to very low (sometimes picomolar to nanomolar) doses of chemicals having estrogenic activity [27].

Most of the steroid hormones and growth factors produced by cows are identical to those produced by humans [78].

Estrogens and Progesterone

It is estimated that in Western world milk products supply about 60 to 80% of ingested female sex steroids [28,24]. Concentration of estrogens in milk has been repeatedly measured and concentrations vary from low to extremely high [24,28-32]. The concentration seems to highly depend on whether cow is pregnant (also which trimester) or not [29,30]. Estrogen and progesterone levels are markedly elevated in dairy products in Western world because most of the milk in the West is produced by pregnant cows, with production enabled both by genetic modification of dairy cows as well as modifications to their feed [62].

Progesterone is a fat soluble hormone and is therefore found in higher concentrations in whole, full fat milk (concentrations range from 1.4 μg/litre in skim milk to about 10 μg/litre in whole milk) [24]. Not only progesterone but also pregnenolone, androstenedione, 17beta-estradiol and estrone increase with the fat content. On average, milk from pregnant cows can contain 500 μg/litre 17β-estradiol (E2), 1 μg/litre estrone (mostly as conjugated ES), and 10 μg/litre progesterone [2].

Of special concern are estrone (E1) [33] and 17beta-estadiol (E2) [34] as toxicological studies have categorized them as carcinogens. Pape-Zambito et al. [30] evaluated the concentration of 17beta-estradiol in milk of more than 200 cows and concluded that concentrations in raw whole milk are negligible and are unlikely to pose a health risk for humans. It has also been reported that the quantity of active estrogens in dairy products (raw and commercial whole milk included) is too low to demonstrate biological activity [31]. Also estrone and 17beta-estadiol concentrations in circulation following consumption of dairy products are insignificant compared to endogenous production rates of E1 and E2 in humans [32,35]. Hartmann [24] also concluded that no hormonal effects can be expected from naturally occurring steroids in food. Others, however argue that milk contains considerable quantities of estrogens [36,37].

The U.S. Food and Drug Administration (FDA) guidelines state that no physiologic effects occur when consumption is ≤1% of the endogenous quantities produced by the segment of the population with the lowest daily production. Estimated total E1 intake from three servings of whole milk represents 0.01%–0.1% of daily production in human beings, making milk and dairy consumption within the range of the accepted daily intake [2].

There are no differences in estrogen content between conventional and organic dairy products [32]. Also pasteurization-homogenization treatment does not significantly affect estrogen concentrations in milk [32].

Human Studies

Study in men and children [25] reported that estrogens found in milk are absorbed in human bodies, and suppress luteinizing hormone (LH) and follicle-stimulating hormone (FSH) production, followed by a decrease in testosterone production. After the intake of 600 ml/m² of cow milk, estrone and progesterone concentrations significantly increased, while LH and FSH concentration gradually decreased in six out of seven men and reached a lowest level 60–120 min after the intake of milk. Serum testosterone concentrations decreased considerably 120 min after intake in all subjects. Urine concentrations of E1, estradiol, estriol and pregnanediol significantly increased in all adults and children. In prepubertal children there is little secretion of estrogens, and serum E2 concentration are undetectable. Therefore, the exposure to small doses of estrogens may have unwanted effects on growth and maturation. An age dependent increase in circulating estrogen was also reported in males who switched from vegetarian diet to Western diet with milk, butter, and meat [38].

Contrary to Maruyama et al. study [25], 12 trained, male, national level judo athletes who consumed 1000 ml of chocolate milk (fat content: 33 g/L) during post-exercise recovery for one week exhibited a trend towards decreased cortisol (and consequently increased testosterone/cortisol levels) with undisturbed testosterone levels [39].

Recent cross-sectional study (2013) among young healthy men in the United States disclosed that intake of full-fat dairy products adversely affected sperm motility and morphology. These conclusions were primarily evaluated from intake of cheese and were independent of overall dietary patterns and weight [40]. Another cross-sectional study (2009) from the Netherlands, however, found that dairy intake was unrelated to semen quality among men attending a fertility clinic [2]. In a prospective investigation, Myriam et al. [41] reported that low-fat dairy foods, especially low-fat milk, were positively associated with sperm concentration and progressive motility resulting in higher total motile sperm counts, however cheese intake was associated with lower sperm concentrations. A possible limitation of infertility clinic population is that results may not be generalizable to men without known fertility problems.

Animal Studies

Interestingly, a more recent study (2012) in rats [42] demonstrated that none of the commercial milk types that we tested contained biologically significant estrogenic activity. It is however unknown if a prolonged consumption of milk could have an estrogenic effect on the consumers. Also, Grugurevic et al. (2016) [43] demonstrated that consumption of native milk from a pregnant cow did not affect plasma E1 and E2 levels in either sex of mice, even with added E1 and E2 which exceeded the physiological concentration of milk estrogens by 1,000 times. On the other hand, Qin et al. (2004) [44] demonstrated that estrogens from milk can cause the growth of mammary tumors in rats.

Insulin-like Growth Factor- 1 (IGF-1)

Insulin-like growth factor I (IGF-1) is a 70 amino acid-linked polypeptide produced by all tissue but mainly by mammary gland and liver [45]. IGF-1 has many potential therapeutic uses because of its varied effects: growth promotion, insulin-like influence on glucose metabolism, and neuroprotection [46]. However, high levels of IGF-1 may increase the risk of the colon, pancreas, endometrium, breast and prostate tumours [47].

The physiologic concentration of cows’ milk IGF-1 from 409 cows ranged from 4 ± 1 nanogram/ml [48]. Since IGF-1 is not destroyed by milk processing especially pasteurisation, it is present in commercial milk [48]. Data about the bioavailability of milk IGF-1 in animals and humans is lacking and it is not clear yet, it is also not clear what amount of IGF-1 in milk could be reached through the gastrointestinal tract [49]. Orally administratered IGF-I in combination with infant formula may be a useful therapeutic tool in infants with compromised intestinal function [49]. However, available data suggests that absorption of orally administered rhIGF-I (highly purified, biologically active, recombinant molecule), even when given in higher doses, is not significant in newborns.

However, human studies have consistently shown that high milk consumption is associated with a 10%–20% increase in circulating IGF-I levels among adults and a 20%–30% increase among children [78]. A study by Rich-Edwards and colleagues [78], reported an immediate stimulatory impact of milk on the secretion of growth hormone and bioactive IGF-I, suggesting that nutrients or bioactive factors in milk may stimulate endogenous growth hormone production. Another human study noted 10% increase in plasma IGF-1 concentration when healthy subjects consumed cow milk, which is actually considered beneficial for bone health [56]. Studies also report that prolonged milk intake maintains IGF-1 levels and may even grow over time [78]. For example, 10-year-old Chinese girls who consumed whole milk had 9% higher IGF-I levels after one year, and 20% higher levels after two years [78], while 12 year-old Britain girls had 10% higher IGF-I levels after 6 months, and 17% higher levels at months 12 and 18 [80].

Bovine Growth Hormone

Bovine growth hormone (bGH) treatment increases cows milk production by increased mammary uptake of nutrients used for milk synthesis. It also changes metabolism in some other tissues, which results in the increased availability of these nutrients for milk synthesis [26]. There are some concerns about the use of recombinant bovine growth hormone (rbGH) in dairy cows due to allegations from news media about potential hazards. BGH administration to dairy cattle also results in increased concentrations of IGF-1 in cow milk [55].

Food and Drug Administration (FDA), concluded that the use of rbGH in dairy cows presents no increased health risk to consumers. Bovine growth hormone is not biologically active in humans, and oral toxicity studies have demonstrated that very high doses of rbGH are not orally active in rats (even though they are responsive to bGH).

Pesticides

Pesticides have been widely used in agriculture; they provide benefits such as increased supply of crops, fruits and vegetables, as well as restrict the trasmission of diseases from insects to livestock. However, many pesticides are neurotoxicants that are acutely toxic at high doses and can potentially exert more subtle effects at lower doses though different exposure routes. [50] Pesticide residues in milk may have a number of potential sources, including environmental (water, soil, and air drift), contamination of the animal feed, or via protection against disease vectors (mites, ticks, and insects). Levels of organochlorine (OC) pesticides in milk have been decreasing over the past decade as most of the developed countries have established maximum residue levels of pesticides in milk and milk products. Since OCs are fat soluble, their residues is mostly found in high-fat dairy products such as cream and butter. [51]

In study [50] which aimed to develop an analytical method for the quantification of insecticide residues in cow milk pesticides, such as azinphos-methyl, and heptachlor epoxide, and the pyrethroid synergist piperonyl butoxide, were detected in a few of the cow milk samples (but in none of infant formulas tested). A 2016 Romanian study which analysed 54 samples of milk and dairy products reported that in most cases, the values of detected OC pesticide residues exceed the maximum residue levels provided by Romanian and international regulations [52]. While, Rastkari, et al. [53] reported that full fat (3%) pasteurized milk from Iran market is safe for consumption as it could not poses potential carcinogenic risk to young children. Kuba, et al. [54] evaluated the content of dichlorodiphenyltrichloroethane (DDT) and its metabolites in cow milk from two regions of Poland. Authors reported that none of the samples exceeded the level above which they should be considered dangerous.

Veterinary Drugs

All antimicrobial drugs administered to dairy animals enter the milk to a certain degree. The most frequently and commonly used antimicrobial drugs are antibiotics used to combat mastitis-causing pathogens and include penicillins, cephalosporins, tetracyclines, macrolides, aminoglycosides, quinolones, and polymyxins. A general concern linked to the widespread use of antimicrobials is the potential development of antibiotic-resistant pathogens, which may then complicate human treatment. [51]

Well designed, interventional, properly controlled human studies are urgently needed to uncover the potential effects of such a popular food on human reproduction and health!

Cancer Risk

In terms of cancer risk, dairy foods have been reported as both protective and occasionally as harmful. As mentioned, carbohydrates in milk are found in the form of lactose, which is generally considered to be of low carcinogenicity [51].

Prostate Cancer

Epidemiological studies suggested that milk consumption is probably as one of the risk factors for prostate cancer. According to the measurements of estrogen levels in milk by several different studies, it was suggested that estrogen in milk was a possible risk to cause prostate cancer [36] and testicular cancer [2]. Increased prostate cancer risk may also be credited to elevated testosterone levels caused by high animal fat intake [58,59]. High milk fat also means higher 17beta-estradiol content which is carcinogen for prostate cancer [44,57]. The high estrogen and IGF-1 content in the milk were considered to be responsible for promoted development of DMBA-induced mammary tumors in animals [44]. A 2016 meta-analysis of 11 population-based cohort studies by Wei Lu et al. [63] reported that consumption of whole milk in men significantly contributed to elevated prostate cancer mortality risk. Interestingly, Pettersson, et al. [65] found that greater consumption of whole milk was associated with worse survival but skim milk was associated with improved survival among men with prostate cancer.

Peter W. Parodi also observed a modest association between milk and prostate cancer in his study and proposed 5 biological explanation [64]:

  • calcium depresses the production of calcitriol, which has antiproliferative properties;
  • the presence of insulin-like growth factor-1, which is associated with cell proliferation;
  • content of fat and saturated fatty acids;
  • branched-chain fatty acids metabolites, which may be carcinogenic;
  • presence of estrogens, which may be carcinogenic

There is quite clear evidence that milk is linked to prostate cancer as well as some age-related diseases, therefore we asked an Associate Professor at the Depertment of Food Science and Technology Faculty of Nutrition Sciences, Amir M. Mortazavian, Ph.D. (Dairy & Probiotic Specialist), to present his opinion for NutrientJournal.com. He told us: “As a philosophical fact, the difference between a drug and poison could be in their dose of consumption. It depends on the body conditions consuming dairy products. For instance, for a cancer-involved person, even low amounts of sugar can stimulate his/her problem, while the sugar in balanced consumption is necessary for calorie intake.” He also added: “Some harmful effects of milk, as other food products, do not refer to their indigenous ingredients, but to their accidental additives and contaminants. Some of these contaminants are known, but many might be unknown, especially in industrial life-style. They might have critical impacts on health.”

Breast Cancer

Evidence for an increase in risk for breast cancer through consumption of cow’s milk and dairy products is contradictory and equivocal. There is some evidence that women who eat full-fat dairy products after early-stage breast cancer diagnosis are more likely to die from breast cancer than women who eat low-fat dairy products [81]. This is not surprising as full-fat dairy is associated with higher estrogen concentrations (compared to low-fat) [24], which is considered a major risk factor. However, in 1453 Italian women diagnosed with breast cancer dairy intake was not associated with breast cancer prognosis, instead high cheese intake was associated with lower mortality [82].

Other Cancers

There are reports about milk being protective against bowel cancer [60,61], and there is some suggestive evidence that it can reduce the risk of bladder cancer [51,61].

Ganmaa et al. [62] hypotesized that female sex hormones in milk and dairy products have a common effect on the development of breast, ovarian and corpus uteri cancers. Further epidemiological and mechanistic studies are needed to verify this hypothesis.

Type 2 Diabetes Mellitus

Interestingly, since the 1960’s there is a steady increase in the prevalence rate of type 2 diabetes mellitus (T2DM) in industrialized countries. This correlates with the introduction of refrigerator and cooling technology, which allowed widespread consumption of fresh pasteurized milk [75]. Obesity, T2DM, metabolic syndrome (as well as some cancers, neurodegenerative diseases and early aging) are all related to persistently increased activation of the nutrient-sensitive kinase mechanistic target of rapamycin complex 1. Correlation between milk consumption and T2DM was also confirmed in a Chinese cohort where a dietary pattern with more meat and milk products was associated with a 39 % greater risk of diabetes [77].

Furthermore, it is speculated that bovine milk microRNA-29b-attenuated BCAA catabolism may be the missing overlooked epigenetic factor that is responsible for the epidemic of T2DM [75].

Post Exercise Recovery

Chocolate Milk for Exercise Fitness BodybuildingCurrent data suggest that endurance athletes or individuals who exercise aerobically can consider chocolate milk as a viable option for post exercise nutrition to support skeletal muscle and whole-body protein recovery [66]. Post-exercise chocolate milk ingestion has been shown to enhance both glycogen resynthesis and later exercise performance. Chocolate milk has been repeatedly found to be superior compared to various commercially available sport drinks as endurance exercise recovery beverage [67-69]. Even though some studies found chocolate milk as effective as other sport drinks [70], it still serves as a more convenient, cheaper, and more tasty recovery beverage option for many athletes. Compared to traditional sports drinks, milk is a more nutrient dense beverage choice for individuals who partake in strength and endurance activities. In national level judo athletes, 1 liter of chocolate milk after exercise was associated with attenuated muscle soreness ratings, reduced cortisol and mood swings and enhanced judo-specific performance [39].

Delayed Onset Muscle Soreness (DOMS)

In humans [39,71] and animals [72], chocolate milk (also omega-3 enriched) has been shown to be a practical, safe and healthy alternative to decrease post-exercise muscle soreness. Interestingly, consumption of raw milk and honey solution immediately after exercise was reported to substantially increase recovery rate compared to chocolate milk [73].

Milk – Mother’s Nutrigenomic Doping System

Milk is an outstanding functional food developed by mammalian evolution to promote adequate growth and development of the newborn mammal. Bodo C. Melnik presented it as a highly sophisticated endocrine signaling system of mammalian evolution that activates the nutrient-sensitive kinase mechanistic target of rapamycin complex 1 (mTORC1). Milk fulfills its mTORC1 activating function by providing fast-hydrolyzed amino acids leucine, glutamine and tryptophan “hardware” and an epigenetic “software” transmitting exosomal microRNA-29b and microRNA-21.

Mechanistic Target of Rapamycin Complex 1

mTORC1 plays an important role in cell growth, protein and lipid synthesis, lipid accumulation and adipogenesis, and muscle protein synthesis. During the period of lactation, milk-driven mTORC1 activation mediates anabolism and the growth of the newborn. However, in the adolescent and adult humans, persistent hyperactivation of mTORC1 increases body weight, lean and fat mass and is of critical concern as it is associated with aging and the development of age-related disorders such as obesity, type 2 diabetes mellitus, metabolic syndrome, cancer, and neurodegenerative diseases. [74] Chronic hyperactivation of mTORC1 also enhances endoplasmic reticulum stress that promotes cell death [75].

mTORC1 is activated by crucial nutrient-derived compounds [74]:

Hyperactivation of mTORC1 signaling is found in many types of cancer cells and leads to unusual increases in protein synthesis and uncontrolled cell proliferation [76]. In this case, milk consumption may have profound negative effects.

MicroRNAs

Two milk-transmitted microRNAs (microRNA-21 and -29b), are obviously involved in the upregulation of mTORC1-dependent translation. It has been estimated that bioactive bovine microRNAs affects more than 11,000 human genes, which may have major nutrigenomic impacts on the process of ageing and the age-related diseases that are not yet recognized [74]. Bovine milk microRNA-21 may overstimulate β-cell mTORC1 activation, while it inactivates FOXO1 (a key transcription factor that plays a central role in the regulation of glucose metabolism, insulin signaling, and β-cell homeostasis ) [75]. With microRNA-29, milk seem to provides a regulatory epigenetic microRNA program that signals to switch off BCAA catabolism in order to increase BCAA levels for the formation of vitally important BCAA-dependent proteins. On the other hand, the microRNA-29 family, (microRNA-29a, b, and c) has been identified as diabetic microRNA markers [75] as they have been reported to cause pancreatic β-cell death (via suppression of myeloid cell leukemia sequence 1 (Mcl-1)) [79] and enhance insulin resistance (via suppression of IRS-1 translation) [83].

Fermented milk products may contain reduced amounts of bioactive milk microRNAs [15].

At present, no direct evidence exists that convincingly demonstrates exosomal and other vehicle mediated uptake of milk miRNAs under physiological conditions [75].

Conclusion

Milk (and dairy products) seem to have both beneficial and adverse effects. However, the proven health benefits of dairy foods may outweigh the harm. Many encourage dairy foods as part of a varied and nutritious diet and as essential to maintain good bone and dental health, to prevent osteoporosis, major cardiovascular disease risk factors, hypertension, type-2 diabetes, metabolic syndromes, as well as some cancers [51].

Some milk constituents such as vitamin D, proteins, calcium, CLA, butyrate, saturated fatty acids may be responsible for observed prospective effects while contaminants such as pesticides, estrogen, and IGF-1 may be responsible for harmful effects [51].

Clearly science is divided and milk’s effects remain rather confusing in the literature so it remains very controversial beverage. Drinking it in moderation should not cause any major harm besides it provides all the essential nutrients. It is even considered a superb, inexpensive and effective post-workout recovery drink. Many bodybuilders even swear by GOMAD (Gallon of Milk A Day) or LOSAD (Litre of Skim a Day). Even though estrogen content is worrying, there was no observed adverse effects in competitive athletes drinking 1 liter after workout. Furthermore, growing children that do not drink cow’s milk have worse bone health, more fractures and even higher BMI.  Nevertheless, children are very susceptible to even extremely small doses of estrogen and observed raise in plasma estrogens in some studies is concerning – to say the least. Therefore, more well conducted, large-scale, long-term experimental clinical trials are URGENTLY needed to clarify the impact of hormones and other contaminants on human health.

Dr. Bodo C. Melnik told for NutrientJournal.com: “the problem of milk and its compounds is that milk is not a simple nutrient but most importantly a signaling system that promotes growth. Growth signaling in the right magnitude is essential for the infant. Accelerated growth in infancy changes axes of metabolic programming and predisposes to our diseases of civilization. Milk promotes the growth of all cells in the body such as muscle cells but also adipocytes. Brain cells don’t need further growth in adulthood. There is a clear association between milk consumption and neurodegenerative diseases such as Parkinson disease. There is a recent meta-anlysis clearly demonstrating that milk consumption increases the risk for prostate cancer. I think these two examples should alert us to stay away from milk, especially pasteurized milk, which transfers exosomes which contain gene-regulatory microRNAs of the dairy cow. These microRNAs resist degradation in the GI tract and most likely reach our blood circulation.”

Many studies were excluded from this review as they were funded by dairy company or by other dairy related associations.

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