There are a lot of bogus claims about autism out there on the Internet. Countless quacks and angry Internet commenters will tell you that vaccines cause autism, despite a lack of scientific evidence to back them up.

Unhelpfully, PETA have also made claims about autism. In a campaign that has recently resurfaced to widespread criticism, PETA linked drinking milk to autism. The campaign has received criticism from a prominent vegan chef, as well as other commentators, both for the unscientific nature of their claims and the negative way it portrays people who have autism. 

In a post that's still on their site, despite numerous people debunking it, PETA say that drinking milk "worsens" autism.

"It isn’t surprising that dairy products may worsen this condition," they write on their site. "Considering that milk has already been strongly linked to cancer, Crohn’s disease, and other serious health problems. Anyone who wants to alleviate the effects of autism should try giving cow’s milk the boot and switch to healthy vegan alternatives instead."

PETA cite a study as well as anecdotal evidence in their post. "More research is needed, but scientific studies have shown that many autistic kids improve dramatically when put on a diet free of dairy 'products'. One study of 20 children found a major reduction in autistic behavior in kids who were put on a casein-free diet (casein is a component of cow’s milk)."

They then say that the reason why dairy "worsens autism" is up for debate, but that "some suggest that the gastrointestinal problems so often caused by dairy products cause distress and thus worsen behavior in children with autism."

The problem is that this isn't the case. PETA cites a study that has just 20 participants, which isn't enough to be recommending dietary changes for anyone. More than that, it's a study that has been discredited by two independent overviews.

The University of Texas looked at 14 other studies that investigated the efffects of casein and gluten-free diets on people with autism, and found that "overall the study quality was poor," and only the least scientific studies said that the diet improved behavior, The Atlantic report.

In short, their campaign linking autism to drinking milk was unscientific, and yet PETA have not taken it down, even after years of being told this.

This isn't even the first time that the campaign has resurfaced and debunked. In 2017 food writer Jack Monroe asked PETA to remove recipes from their website because of the campaign.

"Hi Peta can you please remove my recipes from your website with immediate effect coz I wrote them with my autism," she wrote at the time. "The thing that makes me maddest about that Peta 'autism' campaign is the frowny face. The deliberate negative stereotyping of autistic folk. The not very subtle undertones of 'oooh you wouldn't want an *autistic* child now would you?'"

She added that "funnily enough when I went vegan? The autism didn't just poof away back into, I dunno, some nearby udders or something."

The food writer, presenter and author went on to write that if you google words like "milk and autism" it is the top result, which remains the case three years later, despite numerous calls to delete the post or clarify that the science is not good.

"There may be plenty of benefits to drinking milk alternatives. PETA should talk about these if they want people to stop drinking milk. Don't play on the fears of parents who are looking for advice on how to raise a child with autism."

A version of this article was first published on 11 September 2017