All About Milk | Precision Nutrition

All about milk
Does it really do a body good?

By Ryan Andrews


In this article we’ll discuss whether milk (and dairy) is an essential food for everyone.  Or whether it’s the dietary evil many make it out to be.

Civilizations began to use milk as a source of nourishment around 8000 BCE.

Although animals used for milk include cattle, goats, sheep, horses, buffalo, yaks, donkeys and camels, cow’s milk is one of the mildest tasting mammalian milks and the most popular.

No culture has ever habitually consumed milk from an animal that didn’t live on grass/leaves, as flesh-eating animals secrete milk with an odd flavor that most people don’t fancy.

Most flesh eating animals also give birth to a litter (think dogs and pigs), which means the mammary system is spread along the length of the torso. Translation: Milking is difficult with big, clumsy human hands.

Cheese is said to have been discovered by an Arab nomad travelling across the desert during the Neolithic period with milk in a container made from an animal’s stomach. The enzymes in the stomach curdled the milk.

Fast forward to the 1800s & 1900s when our relationship with dairy cows changed. Populations increased and the importance of calcium and phosphorus for skeletal health became evident.

Milk was promoted by public education campaigns and doctors as a rich source of these minerals. Doctors considered milk as an “indispensible” component of a child’s diet based on this association.

The industry responded to the demand and milk came from cows crowded into dirty milking sheds. Lots of cows, lots of dirt, and little space meant sick cows.

There was concern of a milk-borne epidemic as this new form of unhygienic milk production took precedence. Dairy farmers tried sterile bottling and disease testing on cows, but problems persisted; thus, pasteurization and refrigeration became common after 1900.

Why is milk processing so important?

Milk ferments unless refrigerated. And bacteria and viruses can be transmitted from animals to humans in the course of handling.


Pasteurization heats milk in a vat to temperatures that microorganisms cannot tolerate.


There are various forms of pasteurization:

  • Original pasteurization (1920s): 145 degrees F for 35 minutes
  • High temperature short time (HTST) pasteurization (1930s): 161 degrees F for 15 seconds
  • Ultra high temperature (UHT) pasteurization (1970s): 280 degrees F for 2 seconds

HTST and UHT are cheap to implement and regulate. With the increasing demand for milk and milk processing, it was no longer cost effective to produce low volume, raw milk. Smaller farms were driven out of business.

Processing milk results in higher amounts of lactose and this is one of the reasons raw milk is promoted by some (although the risk of milk-borne disease increases).


Homogenization crushes milkfat globules so small that they cannot rise to the surface and form a cream layer. This helps mix added fat soluble vitamins, but can turn raw milk rancid, so pasteurization must also take place.

Homogenization didn’t gain acceptance until the 1930s when cardboard and opaque milk containers were introduced. Before then, the cream line was visible through glass bottles and used by consumers to gauge the richness of milk.


What you should know about milk production today

Cows have a nine month gestation period and lactate only when they’ve recently given birth, just like humans. In the past, dairy farmers would allow cows a seasonal reproductive cycle, and birth was planned in sync with the new grass of spring.

This way, the mother had lots of nutritious grazing and time to replenish nutrient stores. Grazing is healthier for cows because it provides fresh air and exercise and grass is what the bovine digestive system is built for.

In contrast, industrial production involves feeding cows grain. More grain means more rumen (stomach) acidity, more thirst, diluted milk and ruminal acidosis. Acidosis leads to ulcers, infectious bacteria, inflammation and growth of E. coli. Antibiotics are administered to offset these ailments.

Current dairy producers inseminate cows just a few months after her previous birth, guaranteeing minimal time between pregnancies. When cows produce milk for longer than one year, their immune systems are compromised and milk quality is diminished.

Not only is this uncomfortable for the cow, it increases pregnancy-triggered estrogens in the milk supply. Estrogens can fuel tumor growth.

Scientists find a soup of suspects while probing milk’s link to cancer

Test-tube studies and studies in adults over the past decade have linked cow’s milk with an excess cancer risk in the prostate, and to a lesser extent in the breast and ovaries.

A new study by researchers at the National Cancer Institute assayed grocery-store milk for 15 estrogens: estrone, estradiol and 13 metabolic derivatives of these female sex hormones.

Estrogens can fuel the growth of many tumors, even in the prostate–and estrogen can do this at amazingly tiny concentrations. Identifying how estrogens’ prevalence varies by milk type, and in what chemical form the hormones occur, required a new assay, which the NCI scientists describe in an upcoming issue of the Journal of Chromatography B.

Overall, skim milk had the smallest quantity of free estrogens. However, the conjugated type that dominated skim milk’s profile, 2-hydroxyestrone, is known to be one of the most reactive and potentially risky of the metabolites. That metabolite’s concentration in fat-free milk was second only to buttermilk’s.

There are also other sex hormones in milk—the “male” androgens and insulin-like growth factor 1. Many studies have linked elevated concentrations of IGF-1 with cancer risk.  

A cow’s life

More pregnancy means more calves. Calves are taken within 24 hours of birth at most farms. Since male calves cannot be raised to produce milk, they are used for veal. The veal industry is a by-product of the dairy industry. Female calves replace their mothers and are then sent to slaughter.

The number of dairy cows in the U.S. decreased from 18 million to 9 million between 1960 and 2005. Total milk production increased from 120 billion to 177 billion pounds during the same period. This is due to strategic breeding and pharmaceutical aid.

Life of a cow (1850) Life of a cow (2005)
  • Grazed on pastures
  • Produced 56 pounds of milk/day
  • Milked for 6 weeks after birth
  • 336 pounds of milk per year
  • Milk = $5/gallon
  • Life span of 20 years before dying of natural causes
  • Raised in confined feedlot w/grains
  • Produced 67 pounds of milk/day
  • Milked for 10 months after birth 
  • 20,000 pounds of milk per year
  • Milk = $3/gallon
  • Life span of 3-4 years before being sent to the slaughterhouse. “Spent” dairy cows are used for the cheapest forms of beef.

Milk consumption patterns

Americans are drinking less milk than they used to, as well as more lower-fat milk, but eating more cheese and way more frozen dairy products (aka ice cream).



  • 34 gallons of milk per person (27 gallons whole & 7 gallons lower fat)
  • 23 gallons of milk per person (8 gallons whole & 15 gallons lower fat)
  • 4 pounds of cheese per person
  • 30 pounds of cheese per person
  • 2 pounds of frozen dairy products per person
  • 28 pounds per person

What you should know about organic vs. conventional milk

Sales of organic dairy are increasing 20-25% each year. Many people assume that “organic” means better in many respects. In some ways this is true.

Organic cows may be fed better. Although organic cows are supposed to only receive organic feed, farmers are not required to feed the cows grass.

Organic cows are less likely to be given hormones. The use of rBST (growth hormone) is prohibited with organic cows. rBST is sometimes given to “conventional” cattle to promote growth and milk production, but is banned in Europe, Japan and Canada because of concerns over human health and animal welfare.

IGF-1 can increase secondary to rBST, increasing the odds of mastitis and decreasing the life expectancy for cows while promoting cancer in humans.

But organic isn’t synonymous with healthy living conditions or humane treatment of animals.

Organic dairy production in the U.S. is concentrated with only a few producers owned by agribusiness conglomerates. Organic dairy farmers generally use the same breed and feed methods as conventional farmers, including concentrated animal feeding operations. Organic milk is processed the same as conventional.

What you should know about milk composition

Cow’s milk is made up of 87% water and 13% solids, including minerals (like calcium and phosphorus), lactose, fats, and proteins (like whey, casein, lactalbumins). Fortification with vitamins A and D is necessary since natural levels are low.

Casomorphins are derived from casein, one of the milk proteins. They have opioid (narcotic) properties (think morphine, oxycodone and endorphins). Casomorphins have addictive properties and decrease bowel motility.

The addictive properties make sense from an evolutionary standpoint as the draw to milk is necessary for infant nutrition, calming and bonding with mom. Human milk casomorphins are about 10 times weaker than those found in cows milk.

What you should know about milk and health

Most of us consume our mother’s milk after birth and then transition to cow’s milk. Lactase production diminishes around age 4.

When more than small amounts of un-soured milk enter the GI tract, lactose passes intact to the intestine. This draws water, producing bloating and diarrhea. Some evolutionary biologists believe that those who have the ability to digest lactose were among groups whose ancestors were dairy farmers.

Humans are the only animals who have ever thought of transferring milk from mammary glands of another species to opaque containers and selling it. Using another creature’s milk for food is a peculiar custom indeed and is still not universally accepted. Most interspecies milk substitutions would be disastrous for newborns because of the crucial matches between milk composition and nutrient needs.

While kids believe drinking milk is the key to bone health, scientific reviews acknowledge the following:

“Scant evidence supports nutrition guidelines focused specifically on increasing milk or other dairy product intake for promoting child and adolescent bone mineralization.” (Lanou 2006)

Milk and calcium

In many parts of the world cow’s milk is a negligible part of the diet, and yet, diseases associated with lack of calcium (e.g., osteoporosis, fracture) are uncommon.

In fact, data suggests that calcium rich dairy foods actually increase calcium losses from the body.

How much calcium we get from the diet really isn’t that important, rather, what matters is how much we retain in the body. Populations consuming the most dairy have among the highest rates of osteoporosis and hip fracture in later life.

While cow’s milk can be high in certain nutrients, it’s difficult to argue that it is “essential” for optimal health.

Milk and chronic diseases

Dairy consumption has been associated with cardiovascular diseases, type 1 diabetes, Parkinson’s disease and cancers. Scientists don’t know if this is specifically due to the dairy fat, casein, or the displacement of other nutritious foods.

Nutrition can alter the expression of genes involved in the development of cancer. Casein, a protein found in cows milk, has been linked to different forms of cancer, with strong associations for lymphoma, thyroid cancer, prostate cancer, and ovarian cancer.

What you should know about milk and the environment

Dairy cows consume large amounts of food, produce large amounts of waste, and emit methane. In fact, in the San Joaquin Valley in California, cows are regarded as worse polluters than cars.

Still, dairy is slightly more energy-efficient than raising animals for meat.

Conventional farm

Organic farm

Soy milk

  • 14 calories of fossil fuel energy produces 1 calorie of milk protein
  • 10 calories of fossil fuel energy produces 1 calorie of milk protein
  • 1 calorie of fossil fuel energy produces 1 calorie of organic soybean protein (for soy milk)

Summary and recommendations

Is it possible to get milk from humanely treated animals that is nutritious, sustainable and tastes good? Yes.

Is this where most milk comes from? No.

With the amount of dairy consumed in North America, sustainable and humane dairy operations are a near-impossibility. If we can discard the concept that guzzling X ounces of milk a day is an obligation, perhaps we would be free to discover different forms of it, better production methods and ration intake.

The most nutritious and best tasting milk comes from healthy animals that spend most of their time outdoors on fresh pasture eating lots of grass supplemented with hay, root veggies and grains. In theory, organic family farmers might be better stewards of land, water and food. Non-dairy milks are likely just as nutritious and better for the environment.

More milk in the diet doesn’t necessarily improve bone health. Indeed, consuming high amounts of milk from processed sources is associated with various forms of cancer, diabetes, cardiovascular diseases and neurological disorders.

“You have to decide: Is there anything good about milk? Other than developing children and malnourished adults, people probably don’t need milk.”
–Oncologist Michael Pollak, McGill University in Montreal

“The key to a healthful diet is to choose naturally nutrient-rich foods, such as dairy foods, first as part of a balanced diet.”
–National Dairy Council

Further resources

Harvard School of Public Health:

National Dairy Council

Milk: It does a body good?

PCRM: Health concerns about dairy products

For extra credit

For mammals (mammals have mammary glands), the first form of nourishment is milk.

Butter is slowly simmered to produce ghee.

Casomorphins from cow’s milk have about 1/10th the pain killing strength of morphine.

Individuals who drink > 2 glasses of milk per day have 3 times the lymphoma risk of those who drink less than 1 glass per day.

Lower fat milks are fortified with vitamin A since the vitamin is fat soluble and disappears with the removal of cream/fat.

In 1929, the milkfat in whole milk ranged from 2.9 percent to 8.4 percent. Whole milk now has an industry standard of 3.25 percent.

Some experts suggest that only certain components of dairy pose health problems, such as the casein. Casein isn’t found in butter or whey.

The word milk comes from the Latin mulgeo, which means to press out by softening with the hand.

Buffalo produce rich milk and more milk than most other animals. The reason it never became a staple for many cultures is due to religious beliefs.

Raw milk contains lower levels of lactose.

Disposable milk containers introduced in the 1930s created more waste.

Milk appealed to nomads due to the ease of transport.

Organic dairy update

Between 2000 and 2005, the number of certified organic milk cows on U.S. farms increased by an average of 25%. To meet the demand, organic production is evolving like conventional production.

Large organic dairies with 200 cows or more are a small portion of the organic dairy population, but account for more than 1/3 of organic milk production.

About 2/3 of organic dairies report that 50% of dairy forage comes from pasture.  About 1/3 of organic dairies report that 75% or more of dairy forage comes from pasture.

Using pasture for dairy feed costs less than higher energy feed sources, and average feed costs per cow decline as more pasture is used.

Organic dairies produce about 30% less milk per cow than conventional dairies.  And organic dairies use more pasture-based feeding.

Pasture-based organic dairies’ total economic costs were about $4 per unit higher than conventional pasture-based dairies, much lower than the average price premium for organic milk in 2005.


Click here to view the information sources referenced in this article.

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