When a high fraction of an agricultural product depends on one variety of plant or animal, that product is in danger from diseases that affect that variety. And there is also the danger that the one variety is unhealthy in some way.

Jo Craven McGinty, in her May 28, 2021 Wall Street Journal article “Most Dairy Cows Are Kissing Cousins, and Scientists Are Worried,” writes:

Holsteins give more milk than any other dairy cow in the country … The entire population provides 94% of the nation’s milk.

But selective breeding—allowing farmers to mate only animals with the most desirable traits—has led to so much inbreeding that virtually all Holsteins in the U.S. and abroad descend from just two bulls.

So, while there are roughly nine million Holsteins in the U.S., the breed’s effective population—a measure of genetic diversity—is just 43, according to an estimate published last year in the peer-reviewed Journal of Dairy Science.

Unfortunately, Holsteins have not only the danger that diseases might arise that spread like wildfire through the breed, they tend to produce milk with the A1 milk protein, which Keith Woodford argues persuasively in Devil in the Milk has a 7-amino-acid peptide that often breaks off and can cause auto-immune problems if it gets past the gut lining and into the bloodstream. My blog post “Exorcising the Devil in the Milk” is a distillation of that book. Casting doubt on the healthfulness of the better part of the milk supply is politically charged enough that government agencies in various countries have made the lack of sufficient research for an open-and-shut case sound as if one should not doubt the safety of A1 milk. But corresponding government agencies in the United States still refuse to declare sugar the clear and present danger to our health that it is. You are better off reading Devil in the Milk or at least my blog post “Exorcising the Devil in the Milk” than trusting government agencies that are sensitive to the commercial consequences of casting aspersions on modal milk.

The concerns about the lack of diversity in dairy cows presents a significant opportunity to shift the herds toward production of safer A2 milk. All that is needed to shift herds over within a decade or so is to give bulls with the A2 genes extra points when choosing which bulls to use in breeding the next generation of cows. (The genetic test is commercially available.) But it does require some level of recognition of the problems with A1 milk.

I have often thought that, for those in the income category of most of my readers, drinking A2 milk instead of milk with substantial amounts of the A1 milk protein is one of the best deals available. a2 branded milk is high quality and good tasting. There is no dimension in which it is inferior to regular A1 milk except on price.

Many people argue that dairy is a problem. I wonder what fraction of the problems they suspect are due to A1 milk. I have written more about milk and dairy in a series of other blog posts:

• Exorcising the Devil in the Milk

• How Important is A1 Milk Protein as a Public Health Issue?

• Is Milk OK?

• 'Is Milk Ok?' Revisited

• Whole Milk Is Healthy; Skim Milk Less So

The last blog post in this list points to another issue of which type of milk to choose: the idea that skim milk is healthier is a myth based on the usual naive version of calories in/calories out logic. (See “How Low Insulin Opens a Way to Escape Dieting Hell” for a more sophisticated version.)

The Standard American Diet leaves a lot to be desired. (See “How to Summarize a Big Chunk of Nutrition Research: Almost Anything You Are Likely to Think Of Is Better Than the Standard American Diet.”) Lack of diversity is one of the problems in the Standard American Diet. Michael Pollan points out how much the Standard American Diet relies on corn. (He recommends counting the number of different species one is drawing food from in a typical day.) The heavy reliance of American dairy on one breed of cows is another lack-of-diversity problem in the Standard American Diet.

We are fortunate to have some inkling of the dangers from A1 milk. That makes decisions easier. To avoid unknown dangers in food, it is good to diversify what one eats. Most food we eat is pretty safe from quick-acting poisons. But slow poisons abound in our food. (See for example “Sugar as a Slow Poison.” Diversifying what one eats can reduce the amount of slow poison one consumes.

For me personally, one unpleasant aspects of knowing what I know about diet and health is that when looking at farms along a highway I am going down I can’t enjoy the sights as well. I often see field upon field growing grains likely to cause people’s insulin levels to spike (See “Forget Calorie Counting; It's the Insulin Index, Stupid”) and then around the bend see large herds of Holsteins currently likely to produce milk with a lot of A1 milk protein. I wish I could look out at more farms producing food that will treat people’s health well.

Note: I have no commercial interests in the foods I write about. (I do hold index funds and other very broad mutual funds which include all kinds of stocks. I almost never read the documents listing the stocks in those funds.)

For annotated links to other posts on diet and health, see:

• Miles Kimball on Diet and Health: A Reader's Guide