May 20 2010

Special Diets Do Not Work for Autism

One of the burning controversies in the autism community is whether or not special diets, specifically gluten-free or casein-free, are of benefit to the symptoms of autism. About 1 in 5 children with autism are on a special diet, and many parents strongly believe it is of benefit, but there has been no scientific evidence to back up their anecdotal observations.

A recent study adds to the evidence for a lack of benefit from such diets. The study is not yet published, but is summarized on the University of Rochester website. The main weakness of the study is that it is small – the study enrolled 22 children and 14 completed the study. It’s strength is that it was tightly controlled. Children were placed on a gluten-free (no wheat and barley) and casein-free (no dairy products) diet for 4 weeks. They were then challenged in a double-blind manner with snacks containing gluten, casein, both, or neither (placebo) and observed for behavior and GI symptoms. The study found no benefit for any outcome measure.

By itself this study is far from definitive and I am sure it will not be the last word. It is a small addition to the growing evidence showing lack of benefit from such special diets in autism.

It should further be noted that the evidence does not support the notion that children with autism have a specific gastrointestinal disorder. A recent consensus statement based upon a systematic review of the literature concluded that no such autism-associated GI syndrome exists and that children with autism should be treated as any child would when they have GI symptoms. It is probable that children with autism may respond to GI symptoms when they occur with a worsening of their behavior. This may then cause parents to associate the behavior with the GI symptoms and falsely conclude that the GI symptoms cause the behavior and the underlying autism. This concept comes up frequently in medicine – differentiating an exacerbating trigger from an underlying cause.

It is also interesting to consider why the general notion that diet can dramatically affect behavior in children (whether typical, autistic, or with other disorders like ADHD) is so widespread despite lack of scientific evidence. Many parents believe that sugar makes children hyperactive, but the evidence does not support this believe – it’s basically a myth. What appears to be happening is simple confirmation bias – which can have a powerful psychological effect on belief. When we think there is a pattern we will tend to seek out, notice, and remember events that seem to confirm that pattern. Meanwhile we ignore or explain away disconfirming evidence. This can leave us with a powerful, even if completely false, sense of confirmation.

A common scenario, which parents have reported to me many times, is that parents will first observe that their child’s behavior has suddenly worsened – they are hyper and out of control. They then ask themselves – why is this happening now – and search for a cause. So they inquire about recent eating and may find that they just had a slice of cheese or bread or a piece of candy. “Aha,” they declare, “it must have been the cheese,” or whatever they found. But they do not realize that they don’t investigate what their child recently ate when they are not acting up, and so they have no baseline for comparison.

Unless someone is familiar with the concept of confirmation bias, it is difficult to impossible to convince them that what they believe they have directly observed is not true – just an illusion or trick of memory. When the topic is emotionally charged, such as a parent’s desire to understand, control, and help their child’s condition, it is even more difficult.

Again – we get back to the need for controlled observation (i.e. science). For individual patients I will often have them keep a written diary of symptoms and possible triggers, and use that as a basis for looking for patterns. This is still not perfect, but much better than raw memory. For the underlying question itself, blinded tests where variables are controlled as much as possible are necessary. We frequently find that effects noticed anecdotaly vanish under controlled observation.This happens so often in the history of science that we can take it as a proven principle that anecdotes are unreliable. They are useful for generating hypotheses to test, but they are worthless for arriving at reliable conclusions.

In a perfect world the scientific data would be the final word on such questions. We all just want to know the truth so that we give optimal treatment, whether to our children or our patients. But we live in the modern world of the democratization of information and expertise. When the science conflicts with anecdote some people choose to believe their anecdotal experience and distrust the science. They form grassroots organizations that take on a life of their own, and increasingly become isolated from and distrustful of the scientific establishment with which they disagree. They start to accuse scientists of “attacking mothers” and not listening to parents, and worse – of being part of a nefarious conspiracy.

That response, of course, is incredibly counterproductive. Some researchers may then overreact and discount parents completely or view them as hostile. The very people who can most benefit from the research become alienated from it. They may then form their own subculture, with their own experts and practitioners to serve their beliefs. They will attract more parents, as they are claiming to have a cure or at least a treatment that is effective. The lay media will generally be worthless to counterproductive in sorting out the situation for the public.

We have seen this very scenario play itself out with the Defeat Autism Now (DAN) community. We have also seen it with the chronic lyme disease community, with patterning, bee venom therapy, and many other diseases and treatments.

I don’t have the magic solution to this problem. I think part of the answer is constant education. We need a more scientifically literate public, and a more skeptically literate public. Scientists also need to be better and more aggressive at dealing with the public and the media, and the media needs to be more responsible and have higher standards when it comes to serious scientific reporting. And I think we need more effective regulation, and we need to specifically eliminate regulation which is designed to facilitate the existence of these medical subcultures that exist outside of the standard of care. And we also need to be vigilant toward the transparency and validity of our scientific institutions to minimize fraud and conflict of interest.

We will see how the autism community responds to this new study. It is small and should not be the final word – but it is soundly negative and does add to the body of research which is pointing away from the conclusion that gluten-free or casein-free diets are helpful in autism. Parents need to understand that the very fact such research is being done means that researchers are listening to parents – that was the only reason for doing such a study in the first place. But while scientists listen to parents to generate hypothesis, in the end they listen to the science, and so should the parents.

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