With that in mind we turn to a recently published brief study:
Autistic enterocolitis: Fact or fiction?
This short paper is primarily a review of some of the existing literature in the field although the authors also give a short synopsis of two cases where GI issues were found in young adults with autism. They also touch on the some the of theories about how GI issues and autism could be linked.
While the authors never directly answer the question of Fact or Fiction they do make clear that they feel there is a need for more study in their closing paragraph:
Although the idea of a shared pathophysiology between GI disease and autism remains controversial, the evidence presented so far warrants further exploration at the very least. Be it an immune-mediated connection, versus a 'brain-gut axis' interplay such as seem in irritable bowel syndrome, the increased prevalence of GI symptoms in this group of patients cannot be denied, nor the added distress that these symptoms could have on an individual who is already communicatively challenged. Clearly, more studies need to be conducted to better define the relationship between ASDs and the GI tract.
I couldn't have said it better.