The lactose tolerance part doesn't really make sense because dairy products are not naturally high in vitamin D. Companies add the vitamin D to milk. Butter is

The lactose tolerance part doesn't really make sense because dairy products are not naturally high in vitamin D. Companies add the vitamin D to milk. Butter is an exception because it is nearly all fat, so it has a lot more vitamin D. But, because butter is nearly all fat, it also doesn't contain much lactose and is usually well tolerated by people with lactose intolerance. I have read that the correlation of latitude and lactose tolerance has to do with the fact that milk was less prevalent in warmer climates because it did not store or travel well. So unless you grew up right around milk producing cattle, your gene pool had little exposure too it and thus little evolutionary pressure to continue to tolerate milk after infancy. By contrast, Europe has a much colder climate and was well suited to dairy cows and storing and shipping dairy products.