Update, October 30, 2018: Make sure to read “Exorcising the Devil in the Milk” as well. There I write: “A1 milk is definitely not OK; A2 milk may well be OK other than a general caution not to consume too much animal protein.” The arguments below are better evaluated after reading “Exorcising the Devil in the Milk.”
I love milk. I also love high-quality cheese. So I am very reluctant (and unlikely) to give up consuming dairy products. But it is important to listen to those who are negative about dairy products and consider their arguments. Above, I take my pretty picture of milk from an otherwise random anti-milk webpage entitled "Myths About Milk You Probably Thought Were True." It mostly tries to attack positive notions about milk.
T. Colin Campbell and Thomas M. Campbell attack milk and other dairy products more directly in their book The China Study:
Animal Protein: The Campbells (father and son) have three basic arguments against milk. The first is that milk, like meat, has a lot of animal protein. I discussed this concern about animal protein in "Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?" There I suggest this rule of thumb for a limit on animal protein per day:
I am thinking of a target of around 7% of calories in animal protein on a typical day, without trying to count up the amount of plant protein. ... The footnote at the end of Colin's passage suggests that 2200 calories a day would be typical for someone weighing 70 kilograms. ... 7% of that is 1 calorie per pound per day. ... about 1/4 of a gram of animal protein per pound of body weight per day.
I found by trying it out that for generic animal foods, you can google "how many grams of protein does [animal food x] have" and get a ready answer (with the specification of a measure of weight nice but often optional). For less generic animal foods—for example mozzarella cheese of a particular brand—one can look on the package. To provide some idea of magnitudes, a large egg has about 6 grams of protein, a cup of milk has 7.7 grams of protein, while a quarter-pound hamburger patty has about 29 grams of protein.
Inhibition of the Body's Production of the Active Form of Vitamin D
The Campbells' second argument against milk and other dairy products are that they inhibit the production of the active form of Vitamin D by providing too much calcium as well as because of the acidic internal environment engendered by animal protein. There is some suggestive evidence that the active form of Vitamin D is helpful in combating autoimmune diseases:
There are experimental animal models of lupus, MS, rheumatoid arthritis, and inflammatory bowel disease (e.g., Crohn’s disease, ulcerative colitis), each of which is an autoimmune disease. Vitamin D, operating through a similar mechanism in each case, prevents the experimental development of each of these diseases. This becomes an even more intriguing story when we think about the effect of food on vitamin D.
The first step in the vitamin D process occurs when you go outside on a sunny day. When the sunshine hits your exposed skin, the skin produces vitamin D. The vitamin D then must be activated in the kidney in order to produce a form that helps repress the development of autoimmune diseases. ... Under experimental conditions, the activated vitamin D operates in two ways: it inhibits the development of certain T-cells and their production of active agents (called cytokines) that initiate the autoimmune response, and/or it encourages the production of other T-cells that oppose this effect. (An abbreviated schematic of this vitamin D network is shown in Appendix C.) This mechanism of action appears to be a strong commonality among all autoimmune diseases so far studied.
The active form of Vitamin D also has other important functions in the body, as a passage from page 171 claims:
... active or “supercharged” D produces many benefits throughout the body, including the prevention of cancer, autoimmune diseases, and diseases like osteoporosis. This all-important supercharged D is not something that you get from food or from a drug. A drug composed of isolated supercharged D would be far too powerful and far too dangerous for medical use. Your body uses a carefully composed series of controls and sensors to produce just the right amount of supercharged D for each task at exactly the right time. As it turns out, our diet can determine how much of this supercharged D is produced and how it works once it is produced. Animal protein that we consume has the tendency to block the production of supercharged D, leaving the body with low levels of this vitamin D in the blood. If these low levels persist, prostate cancer can result. Also, persistently high intakes of calcium create an environment where supercharged D declines, thus adding to the problem. So what food substance has both animal protein and large amounts of calcium? Milk and other dairy foods. This fits in perfectly with the evidence that links dairy consumption with prostate cancer. This information provides what we call biological plausibility and shows how the observational data fit together. To review the potential mechanisms:
Animal protein causes the body to produce more IGF-1, which in turn throws cell growth and removal out of whack, stimulating cancer development.
Animal protein suppresses the production of supercharged D.
Excessive calcium, as found in milk, also suppresses the production of supercharged D.
Supercharged D is responsible for creating a wide variety of health benefits in the body.
Persistently low levels of supercharged D create an inviting environment for different cancers, autoimmune diseases, osteoporosis, and other diseases.
Here, from page 385, is a discussion of how milk might inhibit the production of the active form of Vitamin D. The active or "supercharged" Vitamin D is called 1,25 D:
Several studies now show that if 1,25 D remains at consistently low levels, the risk of several diseases increases. So then the question is: What causes low levels of 1,25 D? Animal-protein-containing foods cause a significant decrease in 1,25 D. These proteins create an acidic environment in the blood that blocks the kidney enzyme from producing this very important metabolite. A second factor that influences this process is calcium. Calcium in our blood is crucial for optimum muscle and nerve functioning, and it must be maintained within a fairly narrow range. The 1,25 D keeps the blood levels of calcium operating within this narrow range by monitoring and regulating how much calcium is absorbed from food being digested in the intestine, how much calcium is excreted in the urine and feces, and how much is exchanged with bone, the big supply tank for the body’s calcium. For example, if there is too much calcium in the blood, 1,25 D becomes less active, less calcium is absorbed, and more calcium is excreted. It is a very sensitive balancing act in our bodies. As blood calcium goes up, 1,25 D goes down, and when blood calcium goes down, 1,25 D goes up. Here’s the kicker: if calcium consumption is unnecessarily high, it lowers the activity of the kidney enzyme and, as a consequence, the level of 1,25 D. In other words, routinely consuming high-calcium diets is not in our best interests. The blood levels of 1,25 D therefore are depressed both by consuming too much animal protein and too much calcium. Animal-based food, with its protein, depresses 1,25 D. Cow’s milk, however, is high both in protein and calcium.
They emphasize the high-frequency nature of this process on page 382:
When needed, some of the storage form of vitamin D in the liver is transported to the kidneys, where another enzyme converts it into a supercharged vitamin D metabolite, which is called 1,25 D. The rate at which the storage form of vitamin D is converted to the supercharged 1,25 D is a crucial reaction in this network. The 1,25 D metabolite does most of the important work of vitamin D in our bodies. This supercharged 1,25 D is about 1,000 times more active than the storage vitamin D. Supercharged 1,25 D only survives for six to eight hours once it is made. In contrast, our storage vitamin D survives for twenty days or more. This demonstrates an important principle typically found in networks like this: the far greater activity, the far shorter lifetime, and the far lower amounts of the 1,25 D end product provide a very responsive system wherein the 1,25 D can quickly adjust its activity minute by minute and microsecond by microsecond as long as there is sufficient storage vitamin D to draw from. Small changes, making a big difference, can occur quickly.
Although the availability of the storage form of Vitamin D may not be that powerful in increasing the production of the active form of Vitamin D, a large enough amount may help significantly. See "Carola Binder—Why You Should Get More Vitamin D: The Recommended Daily Allowance for Vitamin D Was Underestimated Due to Statistical Illiteracy."
Personally, the thing I find reassuring in relation to any suppression of the production of the active form of Vitamin D by milk, cheese or animal protein in general is that any substantial period of fasting is likely to provide a period of time in which "supercharged" Vitamin D production will be uninhibited. In other words, in relation to the production of the active form of Vitamin D, it is constant consumption of milk and dairy products, or other animal protein that would cause the biggest problem. If there are frequent breaks from milk, dairy and animal protein consumption--as fasting for, say, 18 hours naturally provides--then there should be substantial chunks of time when the active form of Vitamin D is produced freely.
The Danger of Diabetes Type 1 from when Infants Drink Cow's Milk, and Possible Autoimmune Problems for Adults:
On page 179, the Campbells claim that having infants drink cow's milk raises the probability of Type 1 diabetes:
In the case of Type 1 diabetes, the immune system attacks the pancreas cells responsible for producing insulin. This devastating, incurable disease mostly strikes children, creating a painful and difficult experience for young families. What most people don’t know, though, is that there is strong evidence that this disease is linked to diet and, more specifically, to dairy products. The ability of cow’s milk protein to initiate Type 1 diabetes is well documented. The possible initiation of this disease goes like this:
A baby is not nursed long enough and is fed cow’s milk protein, perhaps in an infant formula.
The milk reaches the small intestine, where it is digested down to its amino acid parts.
For some infants, cow’s milk is not fully digested, and small amino acid chains or fragments of the original protein remain in the intestine.
These incompletely digested protein fragments may be absorbed into the blood.
The immune system recognizes these fragments as foreign invaders and goes about destroying them.
Unfortunately, some of the fragments look exactly the same as the cells of the pancreas that are responsible for making insulin.
The immune system loses its ability to distinguish between the cow’s milk protein fragments and the pancreatic cells, and destroys them both, thereby eliminating the child’s ability to produce insulin.
The infant becomes a Type 1 diabetic, and remains so for the rest of his or her life. This process boils down to a truly remarkable statement: cow’s milk may cause one of the most devastating diseases that can befall a child. For obvious reasons, this is one of the most contentious issues in nutrition today.
They summarize this argument on page 182:
It seems to me that we now have impressive evidence showing that cow’s milk may be an important contributor to Type 1 diabetes. When the results of all these studies are combined (both genetically susceptible and not susceptible), we find that children weaned too early and fed cow’s milk have, on average, a 50–60% higher risk of Type 1 diabetes (1.5–1.6 times increased risk). The earlier information on diet and Type 1 diabetes was impressive enough to cause two significant developments. The American Academy of Pediatrics in 1994 “strongly encouraged” that infants in families where diabetes is more common not be fed cow’s milk supplements for their first two years of life. Second, many researchers have developed prospective studies—the kind that follow individuals into the future—to see if a careful monitoring of diet and lifestyle could explain the onset of Type 1 diabetes. Two of the better known of these studies have been under way in Finland, one starting in the late 1980s and the other in the mid-1990s. One has shown that cow’s milk consumption increases the risk of Type 1 diabetes five- to sixfold, while the second tells us that cow’s milk increases the development of at least another three to four antibodies in addition to those presented previously. In a separate study, antibodies to beta-casein, another cow’s milk protein, were significantly elevated in bottle-fed infants compared to breast-fed infants; children with Type 1 diabetes also had higher levels of these antibodies. In short, of the studies that have reported results, the findings strongly support the danger of cow’s milk, especially for genetically susceptible children.
I find this quite scary in relation to feeding infants cow's milk. It also makes me worry that milk and other dairy products could have autoimmune effects on some adults. I am intrigued by the idea that absorption through the walls of the intestine before complete digestion could heighten autoimmune dangers. It also occurs to me that along the lines of the Campbell's thinking, it would be the combination of the initial autoimmune reaction from milk proteins and insufficient "supercharged" Vitamin D production that creates the greatest danger of autoimmune problems for adults. Periods of fasting would take away one of the two contributions to the danger.
I find myself somewhat at sea trying to evaluate the seriousness of dangers from milk and other dairy products. I would be glad to hear readers' perspectives on milk.
Don't miss these other posts on diet and health and on fighting obesity:
Julia Belluz and Javier Zarracina: Why You'll Be Disappointed If You Are Exercising to Lose Weight, Explained with 60+ Studies (my retitling of the article this links to)
Also see the last section of "Five Books That Have Changed My Life" and the podcast "Miles Kimball Explains to Tracy Alloway and Joe Weisenthal Why Losing Weight Is Like Defeating Inflation." If you want to know how I got interested in diet and health and fighting obesity and a little more about my own experience with weight gain and weight loss, see my post "A Barycentric Autobiography."