From Forbes' Pharma & Healthcare Blog
By Emily Willingham
October 17, 2013
A persistent question in the world of autism is whether or not autistic people have a greater tendency than non-autistic people to have sensitivities to wheat and milk proteins. Research results are mixed, but anecdotally, many parents of autistic children report improvements when they remove wheat and/or dairy from their child’s diet.
Excluding the latter might be particularly risky, according to a new study. Many autistic people have very specific food preferences, and autistics tend to be low on vitamin D and calcium, so cutting a major dietary source of these nutrients requires care and caution.
But what about wheat and autism? Another recent, very large analysis found a complex relationship between autism and wheat sensitivity. Most headlines stated simply that the study authors found no link between autism and celiac disease. The reality is more complex and opens up an issue that I’ve not seen anyone address yet for autistic people.
The investigators found no association whatsoever between having an autism spectrum disorder (ASD) and having a celiac diagnosis. That’s pretty clear. What gets less clear, however, is what they found when they looked at associations between positive results for a blood test for celiac and the presence of an autism diagnosis. A diagnosis of celiac requires a positive blood test result–the test measures antibodies to wheat proteins–and confirmation of the presence of intestinal inflammation, as well. People who test positive for the antibodies but have a normal intestinal lining are not considered to have celiac disease.
This recent study of autism and celiac relied on Swedish databases with health information for a quarter million people. The authors homed in on diagnoses of celiac disease, a serious immune disorder in which the body attacks its own intestinal lining if a person eats foods with gluten, a wheat protein, or other, similar proteins. Consumption of these proteins causes inflammation of the small intestine and symptoms can hit an array of body systems, including bones, skin, and the nervous system.
In this study, having a positive antibody blood test for wheat proteins and having an ASD diagnosis were linked. In other words, someone with an ASD diagnosis was more likely to have a positive blood test for celiac, even though the intestinal exam was normal. There was no celiac, but there was an immune response to wheat proteins.
According to the study’s lead author, Jonas Ludvigsson, one possible explanation for this association is that clinicians are more likely to test someone with an ASD diagnosis for celiac, given the persistence of a suggested link between the two. It might be that if the non-ASD population were tested as much, the exceptional link between ASD and a positive blood test would disappear. According to Reuters:
Ludvigsson cautioned that the link between ASDs and a positive celiac blood test is based on a small number of cases. There could be a real relationship between the two or it could be a result of doctors overtesting people with ASDs, he said. ”I want to underline that the positive association we found in this small group could be by chance,” Ludvigsson said.
That is possible, and only further studies will clear that question up. But I’d like to offer another possible explanation. A Cochrane review found that current evidence for effectiveness of a gluten-free/casein-free diet is “poor,” but one single-blind study found some hints of effectiveness of such a diet for a subset of autistic people. One thing that seems to have gone unvisited in any of these studies is the question of which might come first: Autism, or wheat sensitivity?
The current consensus is that a “leaky gut” on its own isn’t sufficient to cause disease, and what remains unknown is if an existing disorder causes a leaky gut–produces gaps in the intestinal barrier that’s supposed to be largely impermeable–or if a leaky gut eventually leads to a disorder. Because studies have yet to show that repair of a “leaky gut” is effective treatment for anything, some authors have suggested that rather than focusing on the gut for therapy, the focus should be on the primary cause underlying the leaky gut.
In the case of autism, which is typically associated with high levels of anxiety and stress, could stress and anxiety be the cause of increased gut permeability?
Stress is sufficiently linked to gut permeability that a rat model of this problem uses stress to trigger the leaky gut in the animals. Restraint and acoustic stress induced in mice is linked to neuro-inflammation and gut permeability. In other words, to quote one abstract, “stress induces increased permeability of the gut.” Indeed, studies indicate that stress can, in fact, lead to “food antigen-related adverse responses” (i.e., antibody attack of proteins ingested in food), in addition to increased intestinal permeability. Could autistic people, who tend to experience high anxiety and stress, be more prone to a leaky gut, allowing wheat proteins to slip past the barrier and trigger the antibody response?
The stress in question here is not “toxins” or metabolic or oxidative stress. It’s stress from anxiety, restraint, emotional distress, and acoustic torture. Is it possible that thanks to a certain paper alleging a link between vaccines and gut, published back in 1998 and later retracted, the research community has since been looking at the gut-autism connection from the wrong vantage point? Perhaps it’s not that gut leakage causes autism, but that the anxiety of autism stresses the gut.
I wonder what inroads we could make for autistic people experiencing gut distress, both as prevention and intervention, if we began to look at this question from the other side. For example, another factor that increases gut permeability is poor nutrition. Perhaps the best response to gut distress in autistic people isn’t an even further restricted diet.