Milk as a superfood: A debunked myth?

Many humans cannot tolerate cow's milk, yet the dairy industry is huge. Prof. Renneberg shares memories and histories about lactose intolerance.

About the esanum blogs: Our columnists take you into their medical lives, offer insights into the everyday lives of doctors and report on topics that are close to their hearts. In this column, Prof. Reinhard Renneberg, a biochemist, takes a closer look at phenomena from medicine, technology and biology.

Lactose intolerance worldwide

My dear grandmother Anna Renneberg avoided fresh cow's milk. And we had Mascha, our own milk cow, in the stable! Good Anna never drank a drop of cow's milk, not even in her beloved morning coffee. She did, however, love and tolerate fermented milk well, i.e. sour milk and cheese.

Was my grandma lactose intolerant? Probably! At that time, however, we were not yet supplied with lactose-free milk products, as we are today. And I myself am probably also lactose intolerant. Even milk in a cup of coffee gives me an uneasy feeling in my stomach. The majority of us adults produce less and less of the human lactose-breaking enzyme lactase after our early months and years. This stops at puberty. Then fresh milk causes us problems.

It may come as a surprise, but fresh milk does not agree with most people on earth. American Anne Mendelson explains the history of milk in Spoiled: The Myth of Milk as Superfood (Columbia), a bestseller since it was released in April 2023. In the earlier book Milk (2008), which also included great recipes, she already ingeniously explored the myth of milk.

The human intestine splits lactose into glucose and galactose

For example, the German Nutrition Society (DGE) recommends 200 to 250 ml of low-fat milk and 2 slices (50 to 60 g) of cheese daily for adults. Milk can also be completely or partially replaced by other dairy products such as yoghurt or buttermilk. US Americans, on the other hand, are recommended to drink 3 glasses of fresh milk per day. 

The human intestine breaks down lactose into its components glucose and galactose in order to process it. Lactase, an enzyme in the small intestine, is responsible for this. If there is a deficiency or loss of activity of lactase, the lactose reaches the large intestine undigested. There, it is fermented by intestinal bacteria, and degradation products, particularly gases, are released. This results in the typical gastrointestinal symptoms of lactose intolerance.

In the case of the frequently occurring primary lactose intolerance, the enzyme activity of those affected decreases over the course of their lives. Lactose is increasingly poorly digested. Drugs such as antibiotics or chemotherapy can also trigger a lactase deficit and thus lactose intolerance.

And how does the largely lactose-sensitive human population consume milk? Partially fermented, in the form of yoghurt, labneh, buttermilk, clabber, sour cream, kumys, kefir and various cheeses. In them, the lactose is converted into a readily digestible lactate. So milk is good for us, but not necessarily in its "fresh" liquid form. Lactase is only present in a small group of people, mostly the descendants of dairy cultures of northern Europe and the British Isles. Now we can take a look at Anne Mendelson's story of milk.

The story of milk 

Anne Mendelson focuses in a few simple, but very crucial questions:

As a young person in the former German Democratic Republic (aka East Germany) from 1967 to 1968, I received a fairly solid education as a cattle breeder. I still love cows and now follow their fate in the hard-nosed market economy with particular sympathy.

Anne Mendelson traces the history and glorification of milk and its apparent benefits from the first domesticated cattle in the Stone Age to the present day. Drinking fresh animal milk was rare until Western experts - who, however, did not know that there were genetic differences in lactose digestion - ranked it highly above fermented dairy products. This is still the case today. For example, 15% of Germans and Swiss are lactose intolerant, but 79% of African Americans and 89% of Southeast Asians are.

This led to the growth of a massive and environmentally destructive industry that turned milk into a cheap mass product. All this is massively and aggressively promoted across Europe and North America. Of particular interest is Anne Mendelson's analyses on the consequences of homogenisation, modern refrigeration, and pasteurisation on milk and the wider context in which these steps of the supply chain occur.

The book Spoiled calls for a healthy, sustainable future in our relationship with milk and the animals that provide it. My recommendation: a must-read.


Anne Mendelson (2023). Spoiled: The Myth of Milk as Superfood. Columbia University Press.