The history of humans drinking cow’s milk is fascinating and not devoid of controversy.

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Our ancestors were milking sheep, goats and cattle long before they were drinking milk. They weren’t drinking it because if they did, it would make them sick: diarrhea, cramps and bloated stomachs. That’s because after weaning, the mammalian gene that produces lactase, the enzyme that breaks down milk sugar lactose into the absorbable components of glucose and galactose, becomes inactive since milk is no longer consumed. Any lactose then ingested travels to the colon, where bacteria digest it and produce gases that cause the symptoms of “lactose intolerance.”

Why did they begin to domesticate animals for milk if they couldn’t drink it? Because they accidentally discovered that under certain conditions, milk turns into cheese, yogurt or kefir, all of which they were able to consume with no problem. They didn’t know this was because lactose-digesting enzymes had found their way into milk from bacteria or from the stomach of calves.

How is it that today we can drink milk without upsetting our digestive tract? Actually, not all of us can. About 70 per cent of East Asians cannot drink milk without experiencing adverse effects but only about five per cent of people of Northern European descent are lactose intolerant, thanks to a chance mutation in Europeans sometime between 3000-1500 BCE that prevented the lactase-producing gene from being switched off. Not only did this mean that milk could be safely consumed, it also provided a survival advantage. Milk is high in nutrients and was usually safer to drink than water, which was often contaminated with........

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