Milk is toxic! Really? So, milk drinkers, have we been poisoning ourselves all this time?

Oh gods, whoever you are: please save me from True Believers. 

Anonymous, 2013

I recite this prayer whenever I am asked, nay interrogated is more apt, about the latest food public enemy number one. For a while, I had run-ins with fructose haters. Then poor old gluten took over as the source of all ills afflicting modern civilization. More recently, I received an email informing me that milk is toxic! Really? All these years I’ve been using milk with my morning cereal, have I been poisoning myself? And all those Scandinavians who are consuming milk by the gallon, what would become of them? In a moment of weakness, I decided to investigate.

A short perusal of the internet will tell you that milk containing the protein β casein of the A2 variety will cause the following afflictions:

  • Diarrhea, cramps, bloating and gas
  • Osteoporosis
  • Arthritis
  • Heart disease
  • Cancer
  • Recurrent ear infections and colic in infants and children
  • Type 1 diabetes
  • Rheumatoid arthritis
  • Infertility
  • Leukemia
  • Autism

What a list! The only thing missing is milk-generated global warming. No, no, wipe the smirk off; bacterial metabolism in the cow’s gut forms methane. And this gas in the cow’s flatus (Latin for the common fart), is a big factor in global warming…

Cow udder image

Now, some of these conditions, such as diarrhea, bloating and gas, are well-known to be caused by lactase deficiency, the enzyme that breaks down the milk sugar lactose to its glucose and galactose components. But what’s the evidence for the protein casein causing all those human plagues?

Turns out that as is true for every cult, milk haters have a guru and a “Bible”. The guru is one Dr. Keith Woodford, and the Bible is his book “The Devil in the Milk”. The devil, as we know, can disguise himself in many forms. In milk, it is disguised as an innocent-looking peptide, called BCM7 which is released from casein during pasteurization.

Food chemists divided casein into type A1, which releases little BCM7, and type A2, which releases much more. The reason for that, for those of you who are intellectually curious, is that about 5,000 years ago a mutation occurred in the gene coding for casein, and a proline was replaced by a histidine. The mutation occurred in Holstein cows, those black and white behemoths that happen to provide most of the milk in Europe and the Americas. And so, for 5,000 years Western Civilization has been poisoning itself.


Before you get alarmed, let’s look at the quality of the evidence. The peptide caused ‘schizophrenia-like, autism-like and a lot of other-like symptoms in rats. Of course, this peptide, 7-amino acids long, does not cross the intestinal wall to enter the circulation. Not to worry, the investigators injected the rats intravenously. How many people are injecting milk intravenously, or for that matter anywhere in their body? One study showed that after incubating BCM7 with nasal mucosal cells, some of the peptide adhered to the cells. So? It might explain nasal congestion in some milk drinkers…Advice to the allergic patient: Don’t pour milk in you nose.

When you don’t have direct evidence, you resort to suggestive evidence. For instance, schizophrenia and autism are more prevalent in A2-drinking countries than in countries that drink milk with A1 casein (Africa, Asia, southern Europe). Epidemiologically, such studies suffer from a fatal flaw: There are known confounding factors (which can be accounted for in the analysis), known-unknowns (which cannot be factored into the analysis), and a multitude of unknown-unknowns (that, by definition, will never be  accounted for). In other words, the main value of such studies is in tantalizing cocktail party conversations.

If the story ended here, no real harm done. Let them drink goat, sheep or camel milk (no devil lurking in those). But when approximately the same kind of people deprive their children of life-saving vaccinations because of the firm belief that it causes autism, schizophrenia, ADHD, etc. etc., this can be fatal.

I think that many, if not all, food fads, both positive (ward off the common cold, inhibit cancer, prevent Alzheimer’s) and negative (causing allergies, causing cancer, causing intestinal disease, causing fogging of the brain), suffer from the same deadly combination: Poor science and uninformed true believers. Trouble is, no matter how convincing the evidence to the contrary, their faith is unshakable. Hallelujah!

Featured photo credit:

Dov Michaeli, MD, PhD
Dov Michaeli, MD, PhD loves to write about the brain and human behavior as well as translate complicated basic science concepts into entertainment for the rest of us. He was a professor at the University of California San Francisco before leaving to enter the world of biotech. He served as the Chief Medical Officer of biotech companies, including Aphton Corporation. He also founded and served as the CEO of Madah Medica, an early stage biotech company developing products to improve post-surgical pain control. He is now retired and enjoys working out, following the stock market, travelling the world, and, of course, writing for TDWI.


  1. You have your A1 beta casein and A2 mixed up. It’s the A1 beta casein that releases BCM7 peptide not the A2. The ancient cow breeds (Jersey, Asian and African) release A2 casein. Please get your facts straight before writing about it. Also if you are going to write about anything relating to the new milk fad write about raw milk and its pros and cons.


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