Milk

"A daily diet that includes two quarts of milk and a quart of orange juice provides enough fructose and other sugars for general resistance to stress, but larger amounts of sugars can protect against increased stress, and can reverse some of the established degenerative conditions."

— Ray Peat

"The presence of lactose in milk, and of fat, to slow absorption of the amino acids, helps to minimize the secretion of cortisol. The main protein of milk, casein, seems to have some direct antistress effects" - Ray Peat

Milk is ecologically efficient, providing refined nutrients from leaves via rumen bacteria, supporting beneficial gut flora and reducing endotoxin. It has antistress effects but is high in growth-promoting amino acids and phosphate; low in iron, beneficial for adults. Combining milk, cheese, and fruits moderates stress hormones. Regular milk and cheese, with nutrients like calcium and vitamins D/K, prevent chronic stress-related diseases including insomnia, hypertension, edema, inflammations, and allergies.

Labels

Untrustworthy labels without legal standards:

• All natural: Description means nothing, since everything it technically "natural"
• Farm fresh: Marketing term, not indicating actual farm conditions; milk may come from confined cows.
• Grass-fed: Claims can be misleading unless certified; cows may primarily eat grain.

Trustworthy labels with legal standards:

• USDA Organic: Requires pasture grazing during full grazing season.
• Certified Humane: Ensures proper space, shelter, and pasture access.
• Animal Welfare Approved: Mandates year-round pasture living, no feedlots or tethering.

A1 Beta-Casein:

Found in milk from breeds like Holstein; may release BCM-7 peptide during digestion, linked to digestive discomfort in some people.

Assume all milk is A1 unless proven otherwise

A2 Beta-Casein:

Found in milk from breeds like Guernsey or Jersey; lacks BCM-7, easier to digest. Goat milk is naturally this type across the breed, not just select individuals as in cattle.

Milk processing

Homogenized

Milk processed under pressure to break fat globules into smaller particles so the fat doesn't separate, creating a uniform texture.

"The pressure breaks the particle of fat up into such a small size that it doesn't separate. Presumably, that makes unstable fats oxidize faster, so it has a small harmful effect. But considering the alternatives in a supermarket, other foods are going to be much more dangerous as oxidants."

— Ray Peat

Peat rejects the popular theory that homogenized fat particles are small enough to pass into and block arteries. Bile already breaks dietary fat into particles of the same size for normal chylomicron absorption into the bloodstream. Homogenization isn't doing anything the digestive system doesn't already do. The specific version of this theory that circulated in the 1970s, that homogenization-liberated xanthine oxidase enters the bloodstream and damages arteries, was reviewed and found unsupported: absorption of the enzyme into the blood was never demonstrated, and no link between homogenized milk intake and serum xanthine oxidase or artery damage was established. Elsewhere he says he doesn't notice homogenization making milk harder to digest and drinks homogenized milk himself for convenience. He has also called homogenized, pasteurized, organic grass-fed milk "not really" a negative.

Sterlizied/UHT

Avoid if possible

Pasteurized

Ok

Flash pasteurized

Better

Canned or powdered

Heat degrades protein. Canned and powdered milk lose significant amounts of lysine, an essential amino acid, during processing. The same heat damage happens to toasted nuts, cereals, and beans. Heated lysine forms a carcinogen when a sugar is present, as it is in soybeans. Fresh whole milk avoids this problem entirely.

Raw

“The difference [between pasteurized and raw milk] isn't enough to worry about.”

— Ray Peat

Legal status and pasteurization requirements vary by region; the main public-health concern with raw milk is pathogen risk (Salmonella, E. coli, Listeria). Pasteurized milk still works for the pro-metabolic pattern described above.

"Pasteurization reduces the content of vitamin B2 and B12 and folic acid very slightly, but the main differences are that raw milk should taste better, and it generally doesn't have the additives that are in most commercial milk."

— Ray Peat

Each cow carries its own particular bacterial balance in raw milk, which varies with diet and season; a bad reaction to raw milk from one cow doesn't mean raw milk in general is the problem.

Milk fractions

Whey

Whey is the liquid protein fraction left after casein curds form during cheesemaking. It digests faster than casein and is commonly sold as an isolated powder marketed for muscle building. Isolated whey (protein without the fat and sugar of whole milk) is a faster, more stress-adjacent amino-acid load for some people than whole dairy. Prefer whole milk, yogurt, and cheese as food; if using whey, pair it with carbohydrate and don't let it replace gelatin balance in the wider diet.

The two milk proteins differ sharply in cysteine content: whey is well established in the food-science literature as the notably cysteine-rich milk fraction (it's the standard protein source used to boost dietary glutathione synthesis for this reason), while casein's cysteine content is comparatively low. Cysteine released during stress or muscle catabolism has antimetabolic, thyroid-suppressing effects that can become toxic at high levels, so this difference gives casein an edge over isolated whey for anyone leaning on dairy protein under chronic stress.

Warm milk with a little sugar or honey before bed is a standard Peat sleep aid: the casein is anti-stress, and milk slows absorption of the sugar, lowering adrenaline and helping older people especially avoid the sleep hypoglycemia that drives nighttime adrenaline surges and insomnia.

Cream

Cream is the high-fat layer of milk, used in cooking, coffee, and desserts. Like butter, it's saturated dairy fat with low PUFA relative to seed oils: a useful tool for calories, not a replacement for whole milk as the primary dairy source. Quality and additives vary in ultra-pasteurized cartons, and calories climb fast at cream's fat density.

Lactoferrin

Lactoferrin is an iron-binding protein present in small amounts in cow's milk and in much higher concentration in colostrum and human milk. In an 8-week double-blind, placebo-controlled trial, 26 Japanese men and women with abdominal obesity took 300 mg/day of enteric-coated bovine lactoferrin. CT-measured visceral fat area fell 14.6 cm² in the lactoferrin group versus 1.8 cm² with placebo, alongside greater drops in body weight and BMI. Whole milk and dairy products carry lactoferrin in far smaller amounts than the enteric-coated tablets used in the trial; the effect hasn't been shown from ordinary dietary intake.

Lactoferrin also binds circulating lipopolysaccharide and blunts its downstream inflammatory signaling, neutralizing some of the toxic effects of endotoxin.

Milk type by fat

Milk is not fattening; drinkers are slimmer due to high-quality protein, saturated fat, and calcium suppressing PTH. Adequate calcium minimizes PTH, boosting energy, reducing inflammation, obesity, metabolic syndrome, dementia, cancer, multiple sclerosis, tooth decay, and high blood pressure. PTH promotes calcification, histamine, and vascular issues; milk lowers it conveniently.

"I think the calcium content is what makes it anti-inflammatory. Calcium increases the oxygen-using ability of the mitochondria, similar to thyroid. Systemically, it suppresses the parathyroid hormone (PTH). PTH is a stress hormone that, when continued too long, contributes to degenerative diseases. Having a chronically high calcium intake gives you a chronically low parathyroid level."

— Ray Peat

Full fat

Good for bulking, if you drink a lot, choose skim, the fat adds up.

Skim

"I think one percent cow milk or reduced-fat goat milk is probably the best source for most people, because if you're working all day on a farm, for example, it's fine to drink a gallon of whole milk because you're spending so many [calories]."

— Ray Peat

"The amount of estradiol in milk is usually much less than one microgram per liter, and it's concentrated in the cream, so low-fat milk has very little estrogen. The cow's diet is probably a more important factor in the estrogen content of milk than pregnancy."

— Ray Peat

Watch out for added synthetic vitamins.

Animal

Goat

"Goat milk contains more copper than cow milk, and copper is important for energy metabolism and blood formation."

— Ray Peat

Does not require homogenization

More digestible, opt for it if experiencing issues.

20 times the taurine compared to cow's.

Cow

"Cow milk is the next best thing to human milk, and sometimes it's better because cow's milk is built on nutrients that have passed through the fermenting rumen and cleaned up, detoxified of lots of things such as unnecessary polyunsaturated fatty acids."

— Ray Peat

Most available and often cheapest type of milk.

Human

See Breastfeeding for maternal-side nutrition. Human milk carries roughly a third the protein of cow's milk (about 1.3 g vs 3.3 g per 100 ml) and a different whey-to-casein ratio (around 60:40 in human milk versus 20:80 in cow's). The standard explanation ties this to growth rate: calves need more protein to grow quickly, while human infants direct comparatively more energy toward brain and nervous-system development, needing more fat and less protein.

John D. Rockefeller drank human milk from wet nurses in his old age as part of his diet.

Camel

Has the least fat compared to all the other milks, only about 4-5 g per cup (240 ml).

Sheep

"I think camel and sheep milk are kind of thick, high on energy and fat, but they would work, but you would get fatter than on low-fat cow milk."

— Ray Peat

Has the most fat of all milks, ~16–17 g per cup (240 ml). Sheep beta-casein carries proline rather than histidine at the BCM-7-forming site, so it's predominantly the A2-type, like goat and most non-Holstein cow milk.

Milk myths and disease claims

IGF and cancer

Milk raises IGF-1, but Peat treats this as one regulatory factor among many rather than an isolated cancer trigger, and points to milk's tracked association with less dementia, not more disease, in long-term population data.

"It has some of the features of insulin, but it and insulin are just two of our regulatory factors. When one of them is slightly distorted, we have so many other regulatory systems that nothing really changes much. [...] A study of radiation effects in Japan looked at all factors of life and diet. They saw that people who didn't drink milk had a much higher risk of becoming demented in old age. A later study in the U.S. saw the same thing: milk has anti-dementia properties."

— Ray Peat

On dairy and specific cancers, Peat separates prostate from other cancers rather than treating "dairy and cancer" as one question:

"Most of the evidence suggests that it increases prostate cancer but decreases other cancers, especially colon, and is protective in other ways. [...] If it decreases many other risks, it's healthful."

— Ray Peat

Osteoporosis

The "milk causes osteoporosis" claim, popularized by comparing high milk-drinking countries' bone-density and fracture stats, doesn't control for Vitamin D status, in Peat's view.

"There is almost an organization of anti-milk people, and that's one of their worst publications. It is unscientific. Much of it is the lack of Vitamin D in those countries. If you compare someone in Vietnam who eats maybe 600 milligrams of calcium from vegetables, and someone in Sweden who might get 2,000 milligrams from milk and cheese, the people in Vietnam are outside a lot getting sunlight and Vitamin D. [...] Since milk production is high in the high-latitude countries, part of that effect is the lack of Vitamin D."

— Ray Peat

He also rejects the "finite osteoblast" premise sometimes used to support the claim, since osteoblasts are continuously renewed rather than drawn from a fixed pool.

Milk allergies

Food allergies have increased in industrialized countries due to degraded food supply from cheap mass production prioritizing durability over health. Industrial agriculture uses toxins, degrades soil, and increases plant defense chemicals like chitinase, causing most new allergies via cross-reactions with latex, fruits, and vegetables. Estrogen induces similar defensive proteins in humans, raising risks of asthma, celiac disease, autoimmune issues, and transplant rejection.

Milk allergies are rare (0.21% in newborns), often misdiagnosed, and outgrown by most children. Whole milk is typically allergen-free; reduced-fat versions may contain contaminants. Carrageenan in products is a strong allergen disrupting calcium. Lactose intolerance stems from bacterial overgrowth linked to hypothyroidism and stress, not permanent enzyme lack; adaptation occurs with regular consumption.

Recipes

From ReciPeatsMexican milk jelly (Gelatina de Leche)

Milk paired with gelatin.

All milk recipes