If you're a regular ACSH reader, you've met “Crazy Joe Mercola,” as my colleague Dr. Josh Bloom fondly refers to him. Once a reputable physician, Mercola is now perhaps the most prominent “alternative medicine” advocate and supplement salesman globally. Over the years, one of his pet issues has been the alleged link between autism and a variety of chemical exposures, most notably vaccines and pesticides, and this has not changed as 2021 comes to a close. Here's Mercola's latest effort, published by the Epoch Times:
Mercola's argument goes like this: the number of autism cases has exploded since the 1960s. Improved diagnosis explains some but not all of this increase. Therefore, one or more environmental factors are to blame for the rise in autism, most likely a combination of “toxic chemicals”:
There’s no single answer to this problem. Since many different toxins can contribute, preventing autism must include the elimination of most toxic exposures. Top suspects include childhood vaccines, the 10 chemicals listed earlier (glyphosate in particular), autoimmune antibodies, gut inflammation, retroviruses and EMF exposure.
A lot has been said in response to Mercola on these issues. So instead of writing a 3,000-word, point-by-point refutation, I want to focus on the good doctor's willingness to ignore or misuse evidence, using one of his favorite boogeymen, glyphosate, as an illustration.
Autism epidemic?
According to the U.S. Centers for Disease Control and Prevention,” Mercola wrote, “the dramatic uptick [in autism] is in part due to improved and more comprehensive identification and diagnosis. However, improved diagnosis alone cannot explain this trend … No, something is going on.”
It's not clear why something has to be “going on.” Well-designed studies published over the last decade or so have shown that broadening the diagnosis to autism spectrum disorder (ASD) to account for a wider variety of symptoms explains the increase in cases.
For example, many people in the 1980s diagnosed with a developmental language disorder, up to 25 percent in one paper, would be “diagnosed unambiguously with autistic disorder” today. More extensive screening, broader public awareness, and expanded health care access have had a similar effect by uncovering previously undiagnosed cases. If this hypothesis is correct, there's been no unexplained increase in autism.
A variety of environmental exposures may contribute to autism, but this doesn't help Mercola's case. For one thing, some of the factors he wants to blame, like vaccination, aren't linked to ASD risk. “Current evidence suggests that several environmental factors including vaccination, maternal smoking, thimerosal exposure, and most likely assisted reproductive technologies are unrelated to risk of ASD,” a 2017 meta-analysis noted. More importantly, the evidence for environmental contributions to autism is still limited, the authors of a 2019 review concluded:
Our understanding of autism etiology could be advanced by research aimed at disentangling the causal and non-causal environmental effects, both founding and moderating, and gene-environment interplay using twin studies, longitudinal and experimental designs. The specificity of many environmental risks for ASD remains unknown and control of multiple confounders has been limited.
Taken together, this research suggests a less scandalous conclusion than Mercola's: there hasn't been a genuine increase in ASD, and we have much to learn about the possible environmental causes in cases that have been diagnosed.
The pesticide connection
Mercola naturally fingered pesticide exposure as one of the overlooked risk factors for ASD:
In 2012, scientists identified 10 chemicals suspected of causing learning disabilities and ASD Of these, glyphosate is a top suspect for the simple reason that exposure to it is so widespread. Research published in 2019 found women exposed to 11 commonly used pesticides — including glyphosate — during pregnancy have a higher risk of having a child diagnosed with autism.
The 2012 article was just a “strategy to discover” the environmental causes of autism; the authors did not produce any new evidence, nor did they mention glyphosate. The 2019 study found that mothers who lived in California counties with high pesticide use gave birth to children with a slightly increased risk of ASD. But the researchers estimated how much pesticide women were likely exposed to three months before pregnancy, during pregnancy, and during the first year of the baby's life based on residential addresses. They had no actual exposure data. Moreover, they “defined exposure as any versus none to a specific substance during a specific developmental period.”
Whether or not the study's results are valid is beside the point here. Mercola wants to explain a “dramatic uptick” in autism rates across the US. An epidemiological study evaluating ASD risk in eight California counties with high pesticide use (relative to most of the US) is asking a much more conservative question. I suspect Mercola knows this, which is why he pivoted in the following paragraph:
Stephanie Seneff, Ph.D., who has spent a large portion of her career studying glyphosate, believes it is a significant cause or contributor to autism. She’s shown glyphosate:
1. Disrupts your gut microbiome
2. Impairs peristalsis — a feature that is exceedingly common in children with autism
3. Inhibits bile acid release by impairing gallbladder contraction — Many autistic children have very pale stool, suggestive of low bile acid levels
4. Impairs digestive enzymes — Many autistic children also have undigested particles in their stool, which suggests a lack of digestive enzymes. And, indeed, glyphosate affects your digestive enzymes, particularly trypsin, pepsin and lipase
Seneff is a computer scientist at MIT. None of her professional work, which centers around “spoken language systems,” is even remotely related to pesticide safety. She has claimed that glyphosate causes all sorts of serious diseases and social ills, everything from obesity, diabetes, and anorexia to school shootings and terrorist attacks. Back on planet earth, research by the National Academies of Sciences has found similar autism rates in different countries regardless of how much glyphosate they use. Seneff's analysis is highly speculative—to say the least.
If you want to add a fun read to your New Year's Eve festivities, Dr. Bloom took Seneff to task last April for blaming the COVID-19 pandemic, in part, on glyphosate exposure. The fact that Mercola takes her arguments on any topic seriously tells us all we need to know.
Cameron English
Director of Bioscience
Cameron English is a writer, editor and co-host of the Science Facts and Fallacies Podcast. Before joining ACSH, he was managing editor at the Genetic Literacy Project.
