In a nutshell, mammals are not designed to consume dairy products past the time of infancy. Think wolf, elephant, whale, dog...Caucasians of Western European decent are also in the group of people who traditionally have a hard time consuming dairy products.I don't agree with the statement about drinking milk as a child. I consumed a TON of dairy products as a child and didn't have a problem whatsoever. But once puberty hit, everything changed. Personally I believe that with the hormonal shift of onset of puberty has something to do with the onset of IBS. (Flux, you aren't required to disagree with this.)There have been some studies of lactose intolerant people increasing their tolerance. The theory claims that after infancy everyone is lactase persistent to some degree - everyone can have just a little bit of, let's say, milk. If that person slowly increases the amount of milk over a period of time, the body with increase the lactase enzyme production to accomodate the need. Personally, I'm not willing to test it since A. I consumed gallons of milk with no problems until age 10 andB. I've already spent too many years in the bathroomSteve Carper's book "Milk is Not for Every Body" has a lot of good information about lactose intolerance. There's also a website you can read for the latest information.Oh yeah, by the way... After 20+ years of severe diarrhea, gas, and pain, last November I found relief with 300 mg of calcium with every meal. No more IBS. : )Good luck!