Warning: I write this post with a minimal and superficial knowledge of the science of diet and nutrition.  I am obviously not in any way, shape, or form, qualified to give medical or dietary advice.

You may have heard claims that autistic people need to exclude particular foods from our diets.  These exclusion diets are one of the most popular types of complementary & alternative medicine intervention in the autism world (Perrin et al., 2012).  Special diets may indeed be the most frequently-used such intervention (Lindly et al., 2017), although others rank special diets second to dietary supplements like vitamins and herbs (Chiston et al., 2010).  The gluten-free, casein-free diet seems to be particularly popular, but there are other exclusion diets as well.

I have a hard time following the logic of exclusion diets as they relate to autism.  Autism is not a biomedical phenomenon: it’s a category that we invented to describe an extremely heterogeneous range of different behavioural phenotypes.  Some individual autistic people may be biologically different from neurotypical people in different ways, but the autistic phenotype itself is not characterized by clear biological features (“biomarkers”). The boundaries of the category if autism have shifted over time and across cultures, which only emphasizes its socially constructed origins.  Now, if autism is a constructed category defined based on behaviour, not a biomedical phenomenon, why would a biomedical intervention (such as an exclusion diet) be related to autism?

It seems to me that an exclusion diet would only make sense in two cases: firstly, if someone had a co-occurring medical condition (e.g., I do know autistic people with coeliac disease – they definitely need exclusion diets), or secondly, if that exclusion diet was healthy for everyone, including neurotypical people.

That said, I’m a bit skeptical about whether exclusion diets really are healthy for neurotypicals (again, absent a legitimate medical condition like coeliac disease or lactose intolerance).  Human beliefs about diet vary widely across cultures, and even medical professionals agree more with public opinion in their countries than with their colleagues from other cultures (Leeman et al., 2011).  It seems like dietary science hasn’t yet advanced to the point that we can achieve scientific consensus on many issues.  Indeed, you may be familiar with how expert thinking has shifted over time on various dietary questions.  Eggs used to be considered unhealthy (because of cholesterol); now they’re healthy (because the cholesterol isn’t the bad kind).

Given this sketchy track record, I think we should be a bit skeptical about reaching sweeping judgements and writing off whole food groups.  Sure, some generalizations are okay.  Factory-made, uber-processed foodstuffs are probably not the best.  But as a general rule, I think we should be aiming to achieve a balanced diet, not the exclusion of foods from our diets.  I think we should be trying to eat a variety of foods, covering a variety of food groups.

Moreover, there are other reasons to be wary of excluding large groups of foods from our diets.  Reid Knight (2017), an autistic person, writes passionately about the negative consequences of being placed on exclusion diets by parents.  Knight learned through experience that nothing bad happened after eating the excluded foods, and Knight then began trying to evade parental supervision and eat these foods as opportunities presented themselves.  Thus, Knight began binge-eating in secret.  The exclusion diets’ only real consequence was to teach Knight to develop unhealthy eating behaviours.

Finally, we have to recall that autistic people often have serious sensory sensitivities, including taste sensitivities, which can lead us to eat a narrower variety of foods than neurotypicals (Chistol et al., 2018).  In some cases, autistic individuals will only eat a small handful of food items.  Every now and again, I see a case report about an autistic child who developed scurvy after eating a restricted diet (e.g., Saavedra et al., 2018), and I’ve also read a report about an autistic child who developed scurvy due to a ketogenic diet (Ahmad et al., 2018).  If we’re already eating unbalanced, restricted diets, the last thing we need is to restrict the diets further by excluding vast ranges of food items!

References

Chistol, L. T., Bandini, L. G., Must, A., Phillips, S., Cermak, S. A., & Curtin, C. (2018). Sensory sensitivity and food selectivity in children with autism spectrum disorder. Journal of Autism and Developmental Disorders, 48(2), 583-591. https://doi.org/10.1007/s10803-017-3340-9

Christon, L. M., Mackintosh, V. H., & Myers, B. J. (2010). Use of complementary and alternative medicine (CAM) treatments by parents of children with autism spectrum disorders. Research in Autism Spectrum Disorders, 4(2), 249–259. https://doi.org/10.1016/j.rasd.2009.09.013

Knight, R. (2017, December 14). Extreme diets damage autistic people. NOS Magazine. Retrieved from http://nosmag.org/extreme-diets-damage-autistic-people/

Leeman, R. F., Fischler, C., & Rozin, P. (2011). Medical doctors’ attitudes and beliefs about diet and health are more like those of their lay countrymen (France, Germany, Italy, UK and USA) than those of doctors in other countries. Appetite, 56(3), 558-563. https://doi.org/10.1016/j.appet.2011.01.022

Lindly, O. J., Thorburn, S., Heisler, K., Reyes, N. M., & Zuckerman, K. E. (2017). Parents’ use of complementary health approaches for young children with autism spectrum disorder. Journal of Autism and Developmental Disorders. https://doi.org/10.1007/s10803-017-3432-6

Perrin, J. M., Coury, D. L., Hyman, S. L., Cole, L., Reynolds, A. M., & Clemons, T. (2012). Complementary and alternative medicine use in a large pediatric autism sample. Pediatrics, 130(S2), S77–S82. https://doi.org/10.1542/peds.2012-0900E

Saavedra, M. J., Aziz, J., & Cacchiarelli San Román, N. (2018). Scurvy due to restrictive diet in a child with autism spectrum disorder. Case report. Archivos Argentinos de Pediatria, 116(5), 684–687. https://doi.org/10.5546/aap.2018.eng.e684