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  • Writer's pictureJoan Rothchild Hardin

Autism: The Gut-Brain Connection

Source: Spectrum: Autism Research News

Autism spectrum disorder (ASD) is “a condition related to brain development that impacts how a person perceives and socializes with others, causing problems in social interaction and communication. The disorder also includes limited and repetitive patterns of behavior. The term “spectrum” in autism spectrum disorder refers to the wide range of symptoms and severity.” (Mayo Clinic, 2019) & (National Institute of Mental Health, 2018)

This spectrum includes conditions previously considered to be separate:

  • Autism

  • Asperger’s syndrome (generally thought to be at the mild end of autism spectrum disorder)

  • Childhood disintegrative disorder

  • An unspecified form of pervasive developmental disorder

Source: My Aspergers Child

Autism spectrum disorder begins in early childhood and eventually causes problems functioning in society — socially, in school and at work, for example. Often children show symptoms of autism within the first year. A small number of children appear to develop normally in the first year, and then go through a period of regression between 18 and 24 months of age when they develop autism symptoms.” (Mayo Clinic, 2019)

Source: iStock


In 2018 the Centers for Disease Control (CDC) said ASD is diagnosed in 1 in 59 children in the US – predominantly in boys: 1 in 37 boys and 1 in 151 girls. (Autism Speaks, 2019)

The rate of diagnosed autism cases in the US has risen steadily and steeply in the last 48 years – from 1 in 10,000 (very rare) in 1970 to 1 in 59 in 2018 (fairly common).

Source: TACA (The Autism Community in Action)


This is what the Mayo Clinic has to say about what causes autism:

Autism spectrum disorder has no single known cause. Given the complexity of the disorder, and the fact that symptoms and severity vary, there are probably many causes. Both genetics and environment may play a role.

  • “Genetics. Several different genes appear to be involved in autism spectrum disorder. For some children, autism spectrum disorder can be associated with a genetic disorder, such as Rett syndrome or fragile X syndrome. For other children, genetic changes (mutations) may increase the risk of autism spectrum disorder. Still other genes may affect brain development or the way that brain cells communicate, or they may determine the severity of symptoms. Some genetic mutations seem to be inherited, while others occur spontaneously.

  • “Environmental factors. Researchers are currently exploring whether factors such as viral infections, medications or complications during pregnancy, or air pollutants play a role in triggering autism spectrum disorder.

“No link between vaccines and autism spectrum disorder

“One of the greatest controversies in autism spectrum disorder centers on whether a link exists between the disorder and childhood vaccines. Despite extensive research, no reliable study has shown a link between autism spectrum disorder and any vaccines. In fact, the original study that ignited the debate years ago has been retracted due to poor design and questionable research methods.

“Avoiding childhood vaccinations can place your child and others in danger of catching and spreading serious diseases, including whooping cough (pertussis), measles or mumps.”

 – Mayo Clinic (2019)


It has long been observed that children with Autism Spectrum Disorder (ASD) suffer from GI problems such as constipation, diarrhea and gastroesophageal reflux . The worse the degree of autism, the more serious the digestive problems.

Source: Dove Medical Press

Research confirms gut-brain connection in autism

Analysis by Dr. Joseph Mercola

June 27, 2019 And some tantalizing research studies on how the gut microbiome influences a baby’s response to vaccines and vice versa, how vaccines influence the gut microbiome. These findings suggest ways to protect infants – and also older children and adults – from potentially harmful effects of vaccines.


Vaccine. 2018 Jul 16;36(30):4433-4439. doi: 10.1016/j.vaccine.2018.04.066. Epub 2018 Jun 13. The influence of the intestinal microbiome on vaccine responses.


There is substantial variation between individuals in the immune response to vaccinations. The intestinal microbiome plays a crucial rule in the development and regulation of the immune system and therefore its composition might affect how individuals respond to vaccinations. In this review, we summarise studies that investigated the influence of the intestinal microbiome on humoral and cellular vaccine responses. To date, only four studies (three in infants and one in adults) have investigated the influence of the intestinal microbiome on vaccine responses. All found an association between the intestinal microbiome and vaccine responses. Despite the heterogeneity in study designs (including different vaccines, schedules, timing of collection of stool and blood samples, analysis methods and reporting of results on different taxonomic levels), findings across studies were consistent: a higher relative abundance of the phylum Actinobacteria (oral and parenteral vaccines) and Firmicutes (oral vaccines) was associated with both higher humoral and higher cellular vaccine responses, while a higher relative abundance of the phylum Proteobacteria (oral and parenteral vaccines) and Bacteroidetes (oral vaccines) was associated with lower responses. Further, well-designed, adequately powered studies using whole-genome sequencing (to include the influence of viruses, fungi and parasites) are needed to investigate in more detail the influence of the intestinal microbiome on vaccine responses. This will help identify strategies to improve vaccine efficacy and duration of protection, particularly in infancy when the intestinal microbiome is more amenable to external influences and plays an important role in the development of the immune system.

Gut microbiota and infant vaccine protocol

Bell, K. (2015). Gut microbiota and infant vaccine protocol. Gut Microbiota for Health,  See:

Why do some children suffer adverse vaccine events while others escape injury? What can be done to limit risk of injury by vaccination? Current CDC (Centers for Disease Control and Prevention) vaccine protocol beginning within 12 hours of birth does not factor gut microbiota as crucial to immune response. Recent study results suggest polymerase chain reaction stool testing be implemented pre-vaccination in order to determine microbiota diversity and potentially assess risk of injury.

A study published in Pediatrics, July 2014, Stool Microbiota and Vaccine Responses of Infants, details the novel finding that Bifidobacteria are associated with greater vaccine response. Bifidobacteria are well-studied and known to have a reciprocal, anti-inflammatory relationship with the host immune system. Along with Lactobacillus, these Actinobacteria are poised to become leading probiotic adjuvants in order to increase vaccine effectiveness. Such adjuvants and probiotic therapy may prove to reduce risk of vaccine injury.

Ample data show that microbiota diversity is positively associated with health in adults. But, according to this study, diversity is not always healthy for infants.

The study found increased diversity of infant microbiota associated with systemic inflammation and reduced vaccine response. Increased populations of microbes such as Clostridia and E. coli and lowered Bifidobacteria were found to reduce vaccine response.

But what if such increased diversity also increases risk of vaccine injury? There are no studies examining this relationship. Yet studies reveal gut-brain mechanisms that can lead to brain and central nervous system (CNS) injury.

The healthy breastfed infant gut is known to be up to 90% Bifidobacteria, comprising several different strains. Gut dysbiosis in adults is generally a matter of overgrown Proteobacteria such as E. coli and reduced or absent commensals such as butyrate-producing Clostridia. Crucial to diversity is a balance of microbes.

Fundamental to the discussion is re-examination of scientific dogma that the womb and fetal gastrointestinal tract are sterile. We now know placental transmission of microbes is a fact and meconium is teeming with life. Children are born at least partially colonized.

A new Washington University paper published in August 2014 illustrates the point, detailing the gut microbe assembly of preterm infants. Patterned progression of bacterial populations in the preterm infant gut reveals gestational age as the overriding factor in colonization. The sequence occurs as follows: first Bacilli flourish, then Gammaproteobacteria such as E. coli become abundant and, finally, ClostridiaBifidobacteria then flourish with breastfeeding. Environmental factors such as c-section vs. vaginal birth and antibiotics do not affect this progression, though may slow it down. This shows that the dynamic nature of the gut microbiota should be taken into account when carrying out studies on infants.

Current vaccine protocol for preterm infants is to treat as full-term when weighing more than 2.2 lbs. Perhaps preterm infants are at greater risk of autism because gut flora are predominantly Gammaproteobacteria at birth and this triggers an adverse immune response upon vaccination. Protective Bifidobacteria and potentially protective strains of Clostridia are not yet developed at birth.

One other issue needing further exploration is that levels of protective Bifidobacteria vary in populations throughout the world, based on ancestral diet and genes regulating host glycans. If data were to show differences between Western cohorts and other cohorts, this might mean some groups are more prone to vaccine injuries. Data on a wide range of vaccine responses is urgently needed to help inform CDC protocols.

Also on the topic of group differences, Mayo Clinic is busy pondering why Somali Americans respond to rubella vaccination with doubled antibodies.  Could it be their gut bacteria? And maternal microbes are now considered influential in fetal blood-brain barrier permeability without consideration of fetal gut microbes.

It appears the CDC immunization schedule should be reviewed to promote vaccine safety and reflect new knowledge based on microbial interaction with the host immune system.


My two cents on a possible connection between childhood vaccinations and autism:

put up charts of increasing rates of autism (see above) & history of childhood vaccinations

The graph below compares the number of vaccinations by country given to children 0-6 years old  – as of 2013. You’ll notice the US was far ahead in the number of vaccines we given to our children.


See the article containing this chart for a vaccine schedule history for the years 1950-2013: History of Vaccine Schedule (, 2014)

The 2014 article notes:

“414% Increase In Vaccines Given to U.S. Children

“In 1950, your child would have received 7 vaccines by the age of 6. Let’s fast forward to 2013.

“If you follow the Centers for Disease Control and Prevention (CDC), American Academy of Pediatrics (AAP), and American Academy of Family Physicians (AAFP) endorsed annual childhood vaccine schedule, your child will receive over 36 vaccines by the time they are 6 years of age!” ( 2014)

That information for children 0-6 in the US is from 2013. Six years later, in 2019, this is the CDC’s recommended vaccine dose schedule for children 0-18 years. See Table 1. Recommended Child and Adolescent Immunization Schedule for ages 18 years or younger, United States, 2019 for this information. (CDC, 2/2019)

There are a lot of doses of vaccines on this table. The CDC has also made available an easier to read chart for parents of children six and under:  2019 Recommended Immunizations for Children from Birth Through 6 Years Old. (, 2018)

Baby immunization,Baby immunization Schedule 2019


Analysis by Dr. Joseph Mercola, June 27, 2019


Autism Speaks. (2019). Autism Facts and Figures. See:

Bell, K. (2015). Gut microbiota and infant vaccine protocol. Gut Microbiota for Health,  See:

Centers for Disease Control & Prevention (CDC). (2018). Immunization Schedules. See:

National Institute of Mental Health. (2018). Autism Spectrum Disorder. See: (12/25/2018). Detailed vaccination schedule for infants and children- Baby immunization,Baby immunization Schedule 2019. See: (2019). Infants and Children Birth through Age 6. See: (2014). History of Vaccine Schedule. See:

© Copyright 2019. Joan Rothchild Hardin. All Rights Reserved.

DISCLAIMER:  Nothing on this site or blog is intended to provide medical advice, diagnosis or treatment.


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