Could someone please explain why adults who were
apparently lactose tolerant all their lives suddenly
become intolerant, especially in their thirties.

I've always been a heavy consumer of dairy products
with no noticeable digestive problems.  I'm 32 years
old.  Then suddenly, about six months ago I developed
chronic diarrhea.  I was initially advised to try avoiding
dairy products, but this only seemed to partially help. (I
now know that this is because I am extremely
intolerant and will have a couple bouts of diarrhea
after eating even just a hamburger bun without Lactaid
pills.  The "hidden" lactose in all sorts of products
made it hard for me to elucidate the cause of my
problem.)

Subsequently, a gastroenterologist told me that
people do not normally become lactose intolerant so
suddenly, and that therefore, lactose couldn't be my
problem.  He proceeded to run every digestive analysis
known to Western medicine, while my problem only
got worse and worse until I could never be more than a
few minutes from the nearest bathroom.

Eventually I educated myself about hidden lactose, and
was able to solve the problem.  Now, I drink Lactaid
100 and eat Tofutti Non-dairy ice cream, chocolate
supreme flavor (no, I'm not getting paid for
promotions!), use non-dairy creamer in coffee, and
carry Lactaid Ultra pills in my pocket.   Since then I
have learned that it is apparently common for this
problem to develop around the age of thirty.

By the way, I am new to this list and learning a lot from
it.  Thanks.  I've found that it is not easy to be an
intolerant minority member in a tolerant majority world
(I live in New York City).

Dave