"Everything you need to know about lactose intolerance"

"among those who are lactose intolerant, most have symptoms before they are 16. That’s not to say that adults can’t develop the condition – people can become temporarily lactose intolerant as a result of gastroenteritis, bowel injury and some other conditions... There are other misconceptions about the condition. For one thing, people who genuinely can’t absorb lactose can drink moderate amounts of milk – up to around 250 millilitres – in a sitting without symptoms, and they may be able to drink drink twice this amount if it is spread throughout the day. They can also usually consume yoghurt and hard cheese without problems, as most of the lactose is broken down by bacteria during their production. But they should avoid goat’s, buffalo’s, sheep’s or yak’s milk, all of which contain similar levels of lactose to cow’s milk."

https://www.newscientist.com/article/dn27938-everything-you-need-to-know-about-lactose-intolerance/