There's a lot of research that contradicts these notions, and also practical advice on how to remedy through food choices, if one is inclined to look into it. As with anything, it's a controversial subject, probably due to the severity of autism and the real difficulties of changing one's diet radically.
those 3 links are effectively from a single source, Dr Natasha Campbell-McBride, who hasn't practiced as an MD for what looks like 20 years. She makes a living out of that miracle diet. She's anti-vax and hasn't published any research about GAPS.
I think her whole scheme is dangerous and would recommend everyone who's considering this diet to look at the negative press around the diet and its proponent. You'll have to look pretty deep into google results to find those, but they're there. I'm not linking them because I'm not qualified to judge their quality besides superficially.
My son has autism. I'd say he's slightly below 'moderate' on the spectrum. We first started him on the GAPS protocol ~5 years ago. We've since evolved our approach and moved onto other dietary protocols (of which there are many—part of the difficulty with studying or treating autism is that it's a diagnosis of a set of behaviors, not of an underlying condition: the underlying conditions are many and varied), but that was the first time we tried something that resulted in observable, material improvements in his quality of life, across a number of different vectors.
When the healthcare establishment shrugs its collective shoulders and tells you that your son is condemned to a life of physical suffering, and being trapped in his own head, you don't wait for the 'experts' to publish studies. You go to work.
I think her whole scheme is dangerous and would recommend everyone who's considering this diet to look at the negative press around the diet and its proponent. You'll have to look pretty deep into google results to find those, but they're there. I'm not linking them because I'm not qualified to judge their quality besides superficially.