A flat white with soy or oat milk has become a common coffee order among millennials, with many citing lactose intolerance for avoiding dairy.
A study shows that people with lactose intolerance have been drinking milk for more than 9,000 years without significant health problems.
Scientists say that the inability to digest lactose posed few problems for old people in good health, and that it just caused some discomfort.
Researchers from University College London (UCL) and the University of Bristol suggest that the ability to tolerate milk was developed in healthy people who survived famine and disease.
“It is probably the most highly selected trait of a single gene to have evolved in Europeans over the past 10,000 years and also in many African, Middle Eastern and South Asian populations,” said UCL Prof Mark Thomas in the journal Nature.
Scientists collected historical data on how much milk was drunk at different times around the world and compared it to when the lactase gene was common.
They found that there was no link between the two, confirming that drinking milk and being able to digest lactose had no evolutionary advantage.
However, the evidence showed that in times of famine and disease, the intolerance could be fatal as severe symptoms caused deadly dehydration and other problems.
It was during these periods that the prevalence of the lactase gene skyrocketed.
The lactase gene was 689 times more likely to be found in a person during times of famine, and 284 times more likely during times of illness.
“If you’re healthy and non-persistent lactase, and you drink a lot of milk, you may experience some discomfort, but it won’t kill you,” says University of Bristol professor George Davey Smith. But “ if you are severely malnourished and have diarrhoea, you have life-threatening problems.”
(© Telegraph Media Group Ltd 2022)
Telegraph Media Group Limited [2022]