Amanda is right, up to a point: double-blind clinical 
testing is the only way to have any real confidence in an 
answer. But in scientific terms, such testing is necessary, 
but not sufficient. In other words, it is just the bare beginning 
of getting it right.

Not only do you need double-blind testing, you also must: 
replicate the testing by an independent group - a single 
experiment is valueless ; have a sufficiently large test 
group - anything done on 20 volunteers is meaningless; 
ensure that your test group is statistically representative 
of the whole - look at the huge tests on men and heart 
attacks which turned out not to be valid when applied to 
women; and keep on testing over time (longitudinal testing) 
- otherwise you don't know what variables affect your results.

In 14 years of study of medical journal articles on lactose 
intolerance, I can categorically say that not one experiment 
met all these criteria. That's right: zero. Even the best results 
are suggestive, but inadequate. And many, perhaps the 
majority of, interesting questions simply cannot be answered, 
because nobody's ever bothered to test them.

The best thing that can be said about journal articles is that 
anecdotal evidence is even worse. It is next to impossible 
for any individual to know or understand all the variables 
about food and digestion, and even the most careful readers 
of ingredients lists can never truly know everything that enters 
their bodies. And even if you could - just because it's true for 
your body doesn't mean it will be true for anyone else's.

While some days I want to beat my head against the wall over 
the futility of it all, I refrain. My head is all I have, after all.<g>
I'll 
take suggestive over random; I'll accept inadequate over nothing; 
I'll let individuals be the best judge of what works for them. The 
evidence does indicate that most LI people can have small  
to medium  amounts of milk products; that lactase pills really 
work; that true milk allergies are fairly rare; that LI symptoms 
are controllable; and that most digestive problems 
have other causes than milk. I'm not sure how far I would go 
beyond that. I'll give general advice on a case-by-case basis 
on my web site, but I won't pontificate on the subject. There's 
much too much we just don't know.

Steve Carper
author of: Milk Is Not for Every Body: Living with Lactose Intolerance
web site: Steve Carper's Lactose Intolerance Clearinghouse
http://ourworld.compuserve.com/homepages/stevecarper