How could we live a civilized life without milk?
Fortunately, we don’t have to.
Milk is our first food, and provides the basic building blocks for
good health, with lifelong benefits. People know that the calcium
in milk helps to build and maintain strong bones and teeth. Milk
and dairy products are the richest source of calcium.
But milk is a natural nutrient power house, providing not
just calcium but also many vitamins and minerals essential for
healthy bodies. It is an excellent source of high quality protein,
vital for brain development and the growth and repair of muscle
tissue. Milk provides vitamin B12 to build red blood cells and
transport oxygen from lungs to working muscles, and vitamin
B2 which facilitates the conversion of food into energy, and is
essential in the development of the nervous system.
Milk delivers vitamin A to help maintain normal vision and
skin. Milk provides phosphorus for our bones and for body cell
energy, potassium to help regulate fluid balance and blood
pressure, niacin to keep enzymes functioning normally, and
carbohydrate for energy. Plus vitamin B1, vitamin B6, folate,
iodine, magnesium, zinc – and more.
Research has identified more than 100 different components in
milk. Evidence is mounting that consumption of milk and dairy
products may reduce blood pressure, dental cavities and the risk
of cancer, while enhancing bone strength and immunity.
Below we have gathered four articles that discuss milk's relation to bone strength, weight loss and breast cancer.
Dietary Protein: An Essential Nutrient For Bone Health
Jean-Philippe Bonjour, MD
Service of Bone Diseases, Faculty of Medicine, University of Geneva, SWITZERLAND
Abstract:
Nutrition plays a major role in the development and maintenance of bone structures resistant to usual mechanical loadings. In addition to calcium in the presence of an adequate vitamin D supply, proteins represent a key nutrient for bone health, and thereby in the prevention of osteoporosis. In sharp opposition to experimental and clinical evidence, it has been alleged that proteins, particularly those from animal sources, might be deleterious for bone health by inducing chronic metabolic acidosis which in turn would be responsible for increased calciuria and accelerated mineral dissolution. This claim is based on an hypothesis that artificially assembles various notions, including in vitro observations on the physical-chemical property of apatite crystal, short term human studies on the calciuric response to increased protein intakes, as well as retrospective inter-ethnic comparisons on the prevalence of hip fractures. The main purpose of this review is to analyze the evidence that refutes a relation of causality between the elements of this putative patho-physiological “cascade” that purports that animal proteins are causally associated with an increased incidence of osteoporotic fractures.
In contrast, many experimental and clinical published data concur to indicate that low protein intake negatively affects bone health. Thus, selective deficiency in dietary proteins causes marked deterioration in bone mass, micro architecture and strength, the hallmark of osteoporosis. In the elderly, low protein intakes are often observed in patients with hip fracture. In these patients intervention study after orthopedic management demonstrates that protein supplementation as given in the form of casein, attenuates post-fracture bone loss, increases muscles strength, reduces medical complications and hospital stay. In agreement with both experimental and clinical intervention studies, large prospective epidemiologic observations indicate that relatively high protein intakes, including those from animal sources are associated with increased bone mineral mass and reduced incidence of osteoporotic fractures.
As to the increased calciuria that can be observed in response to an augmentation in either animal or vegetal proteins it can be explained by a stimulation of the intestinal calcium absorption. Dietary proteins also enhance IGF-1, a factor that exerts positive activity on skeletal development and bone formation. Consequently, dietary proteins are as essential as calcium and vitamin D for bone health and osteoporosis prevention. Furthermore, there is no consistent evidence for superiority of vegetal over animal proteins on calcium metabolism, bone loss prevention and risk reduction of fragility fractures.
Key teaching points:
- Nutrition plays a major role in the development and maintenance of bone structures resistant to usual mechanical loadings.
- In addition to calcium in the presence of an adequate vitamin D supply, proteins represent a key nutrient for bone health, and thereby in the prevention of osteoporosis.
- Experimentally selective deficiency in dietary proteins causes marked deterioration in bone mass, micro-architecture and strength, the hallmark of the osteoporosis disease.
- Clinically large prospective epidemiologic studies indicate that relatively high protein intake is associated with increased bone mineral mass and reduced incidence of osteoporotic fracture.
- Low protein intake is often observed in patients with hip fracture and intervention study demonstrates that following orthopedic management, protein supplementation attenuates post-fracture bone loss, increases muscles strength, reduces medical complications and hospital stay.
- There is no consistent evidence for superiority of vegetal over animal proteins on calcium metabolism, bone loss prevention and risk reduction of fragility fractures.
Journal of the American College of Nutrition, Vol. 24, No. 6, 526S–536S (2005)
Published by the American College of Nutrition
Link to the paper: http://www.jacn.org/cgi/content/abstract/24/suppl_6/526S
Newer Perspectives on Calcium Nutrition and Bone Quality
Robert P. Heaney, MD, and Connie M. Weaver, PhD
Creighton University, Omaha, Nebraska (R.P.H.), Purdue University, West Lafayette, Indiana (C.M.W.)
Abstract:
It is now generally accepted that an adequate calcium intake is important for building and maintaining a skeleton that expresses quantitatively the full genetic program and reduces lifetime fracture risk. In this brief review we focus mainly on a new and growing body of evidence indicating a benefit of adequate calcium intake on qualitative features of the skeleton that, independent of the quantity of bone, themselves influence skeletal strength and fragility.
Change in bone mass and size during growth are dependent on both calcium intake and exercise, with the largest differences being observed in prepubertal children who have both high exercise levels and high calcium intakes. Much of this benefit is expressed as increased bone diameter (and hence stiffness). Fracture risk peaks at about the time of puberty and is inversely related to bone mass. However, even prepubertally, children with low calcium intakes have been reported to have a fracture rate 2.7 x that of their birth cohort.
Bone remodeling triples from age 50 to 65 in typical women and is now recognized to have primarily a homeostatic basis. While remodeling improves bone strength by repairing acquired defects, homeostatic remodeling, while necessary to maintain blood calcium levels, contributes only structural weakness to bone.
High calcium intakes in postmenopausal and older women reduce this homeostatic remodeling to approximately pre-menopausal values and improve bone strength immediately, well prior to any appreciable change in bone mass.
Key teaching points:
- Low bone mass is associated with increased fracture risk in children, just as in adults.
- Low dairy intake is one of the causes of reduced bone mass during growth.
- Physical activity and calcium intake interact during growth, with the largest accumulation of bone being concentrated in children with high physical activity and high calcium intakes.
- Bone remodeling, necessary to repair or reshape bone, also serves calcium homeostasis; on prevailing diets, homeostatic remodeling is larger than structural remodeling, tripling in magnitude from the premenopausal years to age 65.
- Homeostatic remodeling, while it provides needed calcium ions to the extracellular fluid, weakens bone locally, wherever in the skeleton it occurs. Available evidence suggests that excessive remodeling is a major cause of osteoporotic bony fragility.
- Reduction in bone remodeling by high calcium intakes produces an immediate reduction in fracture risk, well before perceptible change in bone mass can occur.
Journal of the American College of Nutrition, Vol. 24, No. 6, 574S–581S (202005) Published by the American College of Nutrition
Link to the article: Newer Perspectives on Calcium Nutrition and Bone Quality
The Role of Dairy Foods in Weight Management
Michael B. Zemel, PhD, FACN
The University of Tennessee, Knoxville, Tennessee
Abstract:
Dietary calcium appears to play a pivotal role in the regulation of energy metabolism and obesity risk. High calcium diets attenuate body fat accumulation and weight gain during periods of over-consumption of an energy-dense diet and to increase fat breakdown and preserve metabolism during caloric restriction, thereby markedly accelerating weight and fat loss.
This effect is mediated primarily by circulating calcitriol, which regulates adipocyte intracellular Ca2+ . Studies of human adipocyte metabolism demonstrate a key role for intracellular Ca2+ in regulating lipid metabolism and triglyceride storage, with increased intracellular Ca2+ resulting in stimulation of lipogenic gene expression and lipogenesis and suppression of lipolysis, resulting in adipocyte lipid filling and increased adiposity. Moreover, the increased calcitriol produced in response to low calcium diets stimulates adipocyte Ca2+ influx and, consequently, promotes adiposity, while higher calcium diets inhibit lipogenesis, promote lipolysis, lipid oxidation and thermogenesis and inhibit diet-induced obesity in mice. Notably, dairy sources of calcium exert markedly greater effects in attenuating weight and fat gain and accelerating fat loss. This augmented effect of dairy products versus supplemental calcium has been localized, in part, to the whey fraction of dairy and is likely due to additional bioactive compounds, such as angiotensin converting enzyme (ACE) inhibitors in dairy, as well as the rich concentration of branched chain amino acids, which act synergistically with calcium to attenuate adiposity; however, these compounds do not fully account for the observed effects, as whey has significantly greater bioactivity than found in these compounds. These concepts are confirmed by epidemiological data as well as recent clinical trials which demonstrate that diets which include at least three daily servings of dairy products result in significant reductions in body fat mass in obese humans in the absence of caloric restriction and markedly accelerates the weight and body fat loss secondary to caloric restriction compared to low dairy diets. These data indicate an important role for dairy products in both the ability to maintain a healthy weight and the management of overweight and obesity.
Key teaching points:
- Dietary calcium modulates circulating calcitriol (1,25-dihydroxyvitamin D) levels that in turn regulate intracellular calcium which affects fat metabolism in human adipocytes.
- Reducing calcitriol levels by increasing dietary calcium results in reduction of body fat in the absence of caloric restriction, substantially increases body weight and fat loss during caloric restriction and reduces weight and fat regain following successful weight loss.
- Dairy sources of calcium are markedly (50–100%) more effective than supplemental calcium in reducing body weight and body fat during caloric restriction. A portion of this additional anti-obesity bioactivity is attributable to the ACE-inhibitory activity of dairy and to the rich concentration of branched chain amino acids.
- This anti-obesity effect of dietary calcium/dairy is supported by cellular mechanistic studies, animal studies human epidemiological studies and clinical trials.
- Incorporating dairy into weight management regimens is associated with significant preservation of lean body mass during caloric restriction.
Journal of the American College of Nutrition, Vol. 24, No. 6, 537S–546S (2005)
Published by the American College of Nutrition
Link to the article: The Role of Dairy Foods in Weight Management
Dairy Product Consumption and the Risk of Breast Cancer
Peter W. Parodi, PhD
Human Nutrition and Health Research, Dairy Australia, Melbourne, AUSTRALIA
Abstract:
It has been suggested in some reports that dairy product consumption may increase the risk of breast cancer. This review gives a brief overview of the etiology of breast cancer and in particular the roles of fat, bovine growth hormone, insulin-like growth factor-1 and estrogens. Evidence from animal studies and epidemiology does not support a role for fat in the etiology of breast cancer. The daily intake of insulin-like growth factor-1 and biologically active estrogens from dairy products is minute in comparison to the daily endogenous secretion of these factors in women, whereas bovine growth hormone is biologically inactive in humans. On the other hand, milk contains rumenic acid, vaccenic acid, branched chain fatty acids, butyric acid, cysteine-rich whey proteins, calcium and vitamin D; components, which have the potential to help prevent breast cancer. Evidence from more than 40 case-control studies and 12 cohort studies does not support an association between dairy product consumption and the risk of breast cancer.
Key teaching points:
- The etiology of breast cancer is still largely undetermined. A women’s reproductive history provides the most consistent evidence for risk, but the relative risk for most risk factors is close to the null value of 1.
- More than 40 case-control and 12 cohort studies do not suggest that dairy product consumption is associated with the risk of breast cancer.
- It has been suggested by some researchers that dairy products may increase the risk of breast cancer due to their content of fat, insulin-like growth factor-1, estrogens or growth hormone. However, the available evidence does not support this association.
- Animal studies and epidemiology do not suggest a role for fat in the etiology of breast cancer. Bovine growth hormone is biologically inactive in humans. Daily intake of insulin-like growth factor-1 and biologically active estrogens is insignificant compared to daily endogenous secretion in women.
- Milk contains rumenic, vaccenic, butyric and branched chain fatty acids, whey protein, calcium and vitamin D, which have the potential to protect against breast cancer.
Journal of the American College of Nutrition, Vol. 24, No. 6, 556S–568S (2005)
Published by the American College of Nutrition
Link to the article: Dairy Product Consumption and the Risk of Breast Cancer
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