Actually, I don't think it would be difficult at all to test this, and that is why I'm surprised that Ebringer has not done it.
Take 100 (say) people, and randomize them into 4 groups of 25. One group receives nothing, one gets the diet, one gets an experimental drug (remicade, say), and one gets placebo.
The treatment effect for the diet would then be the response in the diet group less the placebo.
This would control for the obvious placebo effect in that people who do not get the diet know they are not getting any possible benefit.
Non-compliance in any of the groups would be dealt with following standard procedures.
Thats about it. It is easy to test in a reasonably scientific way.
I'm not saying that the diet does not work, however, I do believe that AS is very susceptible to personal belief (witness 30% placebo effect in recent anti-TNF studies, and also people with poor prognosis are often high stress/anxiety), so it is not surprising that alot of people who go on the diet improve. And of course, with some exceptions (see a post above) we don't usually hear from people for which it does nothing.
Ebringer is a respectable scientist with interesting and creative ideas. However, if he truly wants to help people with his diet then he should have it rigorously tested and then published in a peer reviewed journal. That's the gold standard for scientific acceptance and until then it would seem that the diet should to be taken with a grain of salt (or two).
I'd be very happy if he (or someone else) would do the work and demonstrate an effect.
