It's very rough, though. I know many (East, South, Southeast) Asians who can drink milk just fine. But I -- white with European ancestry -- am lactose intolerant. Not a really useful rubric from my perspective, and I think if a doctor (re: your "medical context") were to say something like, "you're Asian so your stomach distress is probably caused by dairy" or "you're white so we should look deeper for some unusual cause of your stomach distress", I would look for a new doctor immediately.
Think about the probabilities. Lactose intolerance in the UK (as a proxy for British Americans) is under 10%, while in my home country it is over 85%. Meanwhile, drinking milk is universal among white American children (it’s served in schools). If a white kid has stomach problems, there’s a 90% chance it’s not lactose intolerance. But if an Asian kid presents with stomach problems, lactose intolerance is probably the single likeliest explanation. And it can be assessed by asking a couple of simple questions.
Our kids are half white so we were unsure if they’d be lactose intolerant. At the first sign of stomach problems in the youngest, we switched him to lactose free milk and the problem went away immediately. If we took him to a doctor we might’ve gone down a whole rabbit hole of dead ends. And if we weren’t aware of the issue and looking out for it, we may have not done anything and just let him deal with the discomfort. After all, kids get tummy aches for a million reasons.
