The ability to digest lactose probably spread like wildfire because it was a genetic mutation and those with the mutation had a new source of nutrition they cou

The ability to digest lactose probably spread like wildfire because it was a genetic mutation and those with the mutation had a new source of nutrition they could take advantage of which helped them survive better than those without. So, as a result, most Europeans now are lactose-tolerant. Personally, as someone of northwestern European ancestry, I seem to do just great with a lot of milk in my diet. But back when I was younger and drank a lot of soda with HFCS, I got fat. But I wouldn't expect someone of, say, Asian ancestry to do so well with a lot of milk; they probably wouldn't even be able to drink it without having a lot of gas problems or needing to add lactase (or buy "Lactaid" brand milk). What we really need is nutrition advice that's tailored for an individual's genetic profile, and probably also of the genetic profile of their gut bacteria.