The myth that milk causes or contributes to autism recently has been getting more attention due to a six year old billboard campaign from PETA. The billboard was thankfully taken down rather quickly but the article about the campaign remains on PETA website (as one of their most popular info pages) and they have continued to push it since. But both then and now this claim has been met with a good deal of skepticism and outrage. One of the recent responses came from Steven Novella writing for the Science-Based Medicine blog. In his post titled PETA Embraces Autism Pseudoscience he writes,
The pattern of evidence reveals that the methodologically poor studies, ones that are liable to confirmation bias, show some effect, but the properly blinded studies tend to show no effect. For example, a 2010 study (although small) observed children with autism on a gluten-free and casein-free diet, and then challenged them with either gluten, casein, or placebo in a blinded manner. There was no difference in behavior observed. A recent 2014 study also showed no association between dairy and behavior in autism.
As an aside, when such studies are pointed out, the emotional argument is sometimes made that we are “attacking mothers” or “criticizing parents.” This is a diversion, however. Our only point is that parents are humans and are subject to the same cognitive biases that we are all subject to. Being a parent does not magically render someone immune to bias. We need controlled and blinded observations so that we can differentiate between a real effect and self-deception. When an effect disappears under proper blinding, the most likely conclusion is that the phenomenon is not real but is an artifact of observational bias.
Given current evidence, that is the best conclusion we can come to regarding the effects of gluten and casein on autism. The evidence for any effect on behavior is weak and likely not real. There is also no credible evidence to suggest that casein plays a causal role in autism. The evidence is overwhelming that autism is a genetic disorder. Clinical signs are evident at least by 6 months of age, if not sooner, and there is evidence that the developmental processes leading to autism begin in the womb.
The science simply doesn’t support PETA on this one. Please check out Novella’s full post for more information. For further reading check out some of the following posts:
The Bad Science Behind PETA’s Claim That Milk Might Cause Autism by Arit John
PETA: Milk Linked To Scary Autism And Vegan Is Your Only Hope by Emily Willingham
PETA Reinvents Science And Medicine, Declares That Milk Causes Autism By Hank Campbell
Also don’t forget to check out my take on other milk myths.