The Wikipedia article on the subject mentions that the number of people who are lactose intolerant as adults is unknown, but goes on to say "One estimate puts the average at 65% of the global population.[8] Rates of lactose intolerance vary between regions, from less than 10% in Northern Europe to as high as 95% in parts of Asia and Africa.[3]"
It goes on to say that evidence suggests that lactase persistence has evolved multiple times independently, so it's not just a one time European mutation.
Far less than 35% of the worlds population is lactose tolerant as an adult. I will take a look at the review linked on wiki and try to see how robust this number is.
Edit. Ok trekking back through the literature the estimate is based on old measures of the lactase persistence phenotype which is not very reliable, not on genetic data. It is likely to be wrong just on demographic growth alone in the last 40 years. My guess is around 15% of the worlds population is actually able to digest lactose in adulthood.
If 5% of the world developed the ability to see UV light would be call the other 95% UV-intolerant.
For the record I am not lactose intolerant my northern European ancestors developed that ability (plus blue eyes, blond hair & red hair).
I've read that too I think it breaks down the lactose sugar molecule which is why lactose intolerant people can eat Greek yogurt (not just any yogurt) and cheese.
It's kind of odd we call people lactose intolerant when probably only 5% of the world is able to digest lactose. The majority of the world cannot digest lactose but that's normal not a disease.