When I finally said “I’m sick of being sick” after having been on half a dozen different types of antacids, treated for ulcers, told I had IBS - I decided to cut out the two most common food sensitivities - gluten and dairy - simultaneously. I have a friend who is both gluten free and dairy free, so I had a fairly good example.
I couldn’t do it. Partly because I then came down with raving insomnia and sort of freaked out (not from the dietary changes, I think the insomnia was unrelated). So I went back to my normal diet and when I started up again, I gave up the easier one - gluten.
Now, I’m not strict - but gluten free these days is pretty easy. Dairy was hard. Soy milk/rice milk - not remotely the same. Gluten free cookies - not too bad.
(Gluten free bread, not the same - but I’ve learned to cope).
Typo, skepticism is almost a religion for me, but the bottom line is that large double blind studies don’t mean much to an individual. If it is true for you and yours then it is true for you and yours. As you say, that is not evidence to support advising it for anyone else but so what? You are not telling anyone else to do it and, other than the fact that restrictive food preferences make mealtimes already a nightmare for some parents of autistic kids and so these restrictions have to be commonly very unfun, there is no harm in a family giving this one a whirl. As a doc I can’t advise it, but I see no reason to advise against it either.