Because I love dairy, I need to keep reanalyzing the evidence about possible downsides to milk and other dairy as I run across relevant articles. Anne Karpf’s article “Dairy Monsters” in the Guardian throws some additional curve balls about milk. Here I am going to limit myself to potential health worries about milk and dairy, leaving aside environmental concerns (which could be important). I will also leave aside lactose intolerance, because that issue is well understood.
Is It Just the Devil in Milk? First, there is a set of issues that could be entirely due to the A1 casein in regular milk, and possibly can be avoided simply by sticking to A2 milk—whether a2 brand cow’s milk or goat milk. See “Exorcising the Devil in the Milk.” Here are passages from the article above about this set of issues that could result from the structural weakness in A2 casein the lets a nasty 7-amino-acid peptide break off:
According to various studies, there's a whole catalogue of other illnesses that can be attributed to cows' milk, among them diabetes. A 1992 report in the New England Journal of Medicine corroborated a long-standing theory that proteins in cows' milk can damage the production of insulin in those with a genetic predisposition to diabetes. The dairy industry dismisses this as "just a theory" - along with "myth" and "controversial", a term it applies to almost all studies critical of milk.
The anti-milk lobby also claims that consumption of dairy products can aggravate rheumatoid arthritis and has been implicated in colic, acne, heart disease, asthma, lymphoma, ovarian cancer and multiple sclerosis.
Don’t Give Cow’s Milk to Infants! In addition, milk with A1 casein in it could be quite dangerous to give to infants, since infants drinking regular cow milk is is linked to Type 1 diabetes (more than where cow herds naturally lean toward the a2 casein). But there is another danger that should make you think thrice about giving infants cow milk:
Frank Oski, former paediatrics director at Johns Hopkins school of medicine, estimated in his book Don't Drink Your Milk! that half of all iron deficiency in US infants results from cows' milk-induced intestinal bleeding - a staggering amount, since more than 15% of American under-twos suffer from iron-deficiency anaemia. The infants, it seems, drink so much milk (which is very low in iron) that they have little appetite left for foods containing iron; at the same time, the milk, by inducing gastrointestinal bleeding, causes iron loss.
Animal Protein is a Problem. Second, there is the general problem that animal protein builds strong cancer cells. On this, see “Meat Is Amazingly Nutritious—But Is It Amazingly Nutritious for Cancer Cells, Too?” and the other posts flagged under “Anti-Cancer Eating” at the bottom of this post. Here is the relevant quotation from Anne Karpf’s article:
Major studies suggesting a link between milk and prostate cancer have been appearing since the 1970s, culminating in findings by the Harvard School of Public Health in 2000 that men who consumed two and a half servings of dairy products a day had a third greater risk of getting prostate cancer than those who ate less than half a serving a day.
In the same year, T Colin Campbell, the Jacob Gould Schurman Professor of Nutritional Biochemistry at Cornell University, said that "cows' milk protein may be the single most significant chemical carcinogen to which humans are exposed".
Not only is animal protein a problem in causing cancer, protein—especially animal protein—can contribute to osteoporosis. Here is Anne on that:
To the milk critics, the shibboleth that osteoporosis is caused by calcium deficiency is one of the great myths of our time (each side accuses the other of myth peddling). Mark Hegsted, a retired Harvard professor of nutrition, has said, "To assume that osteoporosis is due to calcium deficiency is like assuming that infection is due to penicillin deficiency." In fact, the bone loss and deteriorating bone tissue that take place in osteoporosis are due not to calcium deficiency but rather to its resorption: it's not that our bodies don't get enough calcium, rather that they excrete too much of what they already have. So we need to find out what it is that's breaking down calcium stores in the first place, to the extent that more than one in three British women now suffers from osteoporosis.
The most important culprit is almost certainly the overconsumption of protein. High-protein foods such as meat, eggs and dairy make excessive demands on the kidneys, which in turn leach calcium from the body. One solution, then, isn't to increase our calcium intake, but to reduce our consumption of protein, so our bones don't have to surrender so much calcium. Astonishingly, according to this newer, more critical view, dairy products almost certainly help to cause, rather than prevent, osteoporosis. …
A study funded by the US National Dairy Council, for example, gave a group of postmenopausal women three 8oz glasses of skimmed milk a day for two years, then compared their bones with those of a control group of women not given the milk. The dairy group consumed 1,400mg of calcium a day, yet lost bone at twice the rate of the control group. Similarly, the Harvard Nurses' Health Study found that women who consumed the most calcium from dairy foods broke more bones than those who rarely drank milk. Another piece of research found that women who get most of their protein from animal sources have three times the rate of bone loss and hip fractures of women who get most of their protein from vegetable sources, according to a 2001 National Institutes of Health study.
Thus, instead of drinking more milk, those worried about osteoporosis would be better advised to avoid animal protein. And exercise may also be a big help against osteoporosis, especially if started young:
A 15-year study published in the British Medical Journal found that exercise may be the best protection against hip fractures and that "reduced intake of dietary calcium does not seem to be a risk factor". Similarly, researchers at Penn State University concluded that bone density is affected by how much exercise girls get in their teen years, when up to half of their skeletal mass is developed. The girls who took part in this research had wildly different calcium intakes, but it had no lasting effect on their bone health.
Are There Countervailing Health Benefits of Milk? Some studies claim health benefits from milk. But:
The critics say these are small studies, in which other dietary and genetic factors, exercise and alcohol may swamp the effects of milk drinking. But couldn't the same accusation be levelled at studies revealing the malign consequences of milk? Not so, say the critics: those studies are far larger, build in the countervailing factors and still come up with a strong correlation between the saturated fats in milk and the risk factors for ill health.
And no claim that milk is essential to human health after weaning can stand up to even a cursory examination. The prevalence of lactose intolerance has led to broad scientific agreement that drinking milk after weaning is a relatively recent innovation for humans, and then only in some ancestries. A large fraction of people today, and in all likelihood an even larger fraction of ancestral humans have drunk very little milk after weaning, and have been fine.
Milk May Get in the Way of Vitamin D. Anne misses at least one important point. Despite talking about the importance of Vitamin D (see “Carola Binder—Why You Should Get More Vitamin D: The Recommended Daily Allowance for Vitamin D Was Underestimated Due to Statistical Illiteracy”) Anne misses T. Colin Campbell’s argument that dairy can inhibit the body’s production of the active form of Vitamin D. (I have a section on this in “Is Milk OK?”).
Balancing the Health Costs and the Culinary Benefits of Milk and Other Dairy. Despite all of this, I don’t intend to give up dairy. Health consequences have to be balanced against the pleasure one gets from a particular food. But how can I minimize any health costs from dairy? Here is my approach:
Stick to A2 milk. On how, see “Exorcising the Devil in the Milk.”
Keep your overall animal protein consumption down. If you love milk like I do, then you should eat less meat and eggs. I recently cut back my egg consumption from two per day to one per day to make more room for animal protein from milk.
Substitute coconut milk for animal milk in anything it tastes almost as good.
Take time off from food, frequently. That is, fast often for at least 16 hours, (a) to make it hard on your cancer cells, (b) to give your body a chance to make the active form of Vitamin D, (c) lower your insulin levels, and (d) to give your body a chance to repair itself in other ways.
Consider milk and other dairy as a special treat and appreciate every bit of it. Try to keep the overall quantity down.
Conclusion. I believe there are many worse foods than milk. For people who don’t have obvious problems with milk, I advise them to worry first about eliminating sugar before worrying about dairy. However, switching to a2 milk is an obvious winner. Few of my readers are in a low enough income category that the extra expense of a2 milk (and goat or sheep cheese instead of cow cheese) will be a big deal, and the likely health benefits are large. Reading “Exorcising the Devil in the Milk” will put you onto an intervention with one of the best benefit/cost ratios in all of the diet and health area. (If you don’t believe me after reading that post, please post a comment on that post and I’ll think about what you have to say.)
Finally, let me emphasize that, in my view, milk fat is not a problem. The only thing I worry about with cream is the small amount of protein in the cream. I have my doubts about the first half of my earlier blog post title “Whole Milk Is Healthy; Skim Milk Less So” but not the second half. Don’t ever drink skim milk and avoid all products made from skim milk! Lowfat products tend to have a high insulin index. (See “Forget Calorie Counting; It's the Insulin Index, Stupid.”) As a result, skim milk is less healthy—and in any case, if you are going to brave the possible health impact from milk, you might as well get the wonderful experience from full-fat milk!
Don’t miss my other posts on diet and health:
I. The Basics
II. Sugar as a Slow Poison
III. Anti-Cancer Eating
IV. Eating Tips
V. Calories In/Calories Out
VIII. Debates about Particular Foods and about Exercise
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)
IX. Gary Taubes
X. Twitter Discussions
XI. On My Interest in Diet and Health
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 “Diana Kimball: Listening Creates Possibilities” and my post "A Barycentric Autobiography.