haven't had cows' milk since '97 (except in the occasional cup of tea) and i'm all the happier for it. When i was in school i did some research on lactose "intolerance" which a lot of people mistake for lactose maldigestion - which is the gas and stomach upset that most people associate with "intolerance" In other words you're stomach is saying "what the hell is this crap that you just dumped down here?" And let's just hope that you're all drinking organic milk b/c you don't want to hear the horror stories (and criminal cases) i dug up on conventional milk.
It turns out, and get this, that milk was designed for baby cows and that humans weren't really designed to digest it. If you start in scandinavia you'd have a rate of lactose malidgestion of about 5% of the population. As you went south towards Italy, Spain, Greece, etc it would steadily increase until it hit around 70% in parts of southern italy.
In africa lactose maldigestion starts at 70% and increases to 95% with the exception of some goat herding tribes in southern africa.
In asia, going east from eastern europe it increases from 30% to around 99% in the far east. The exception here is northern india and the himalayan region coming in around 15-20%
In the US it's the same thing - a significant portion of the black, asian, italian, and latino population can't handle the the amount of dairy they're told they have to eat.
As for lactose intolerance, it's really a much more severe symptom where milk proteins triggers an IGB (immune system) response that a lot of people pass off as allergies. They're right, it is an allergy, to the milk. It can also exacerbate other things like allergies to ragweed, pollen, and even other foods.
It's really crazy that people go out of their way to buy reduced fat or reduced lactose milk - if it doesn't agree with you you're body is trying to tell you something - just don't drink the stuff.