Scientific evidence and other considerations in the use of prebiotics and probiotics in Autism Spectrum Disorders
The Autism Spectrum Disorders (ASD) They are a diverse set of neurodevelopmental disorders whose pathognomonic characteristic is the difficulties that patients present in their communication and sociability abilities.
The fact that the term ASD encompasses diverse neurodevelopmental problems that do not stem from a single etiopathogenic cause means we must question any treatment presented to us from a holistic perspective. In other words, if these problems have diverse causes, it would be practically impossible for the same treatment to be beneficial for "any" of the conditions included within ASD.
Since the 80s, we have been repeatedly told that certain dietary adjustments can be beneficial for patients with ASD. Today, we could say that such claims fall under what is known as neuromythsIn other words, certain partial positive findings could lead to a generalization about the benefits. For example, eliminating some nutrients can improve gastrointestinal symptoms in patients with ASD, just as it would in any other individual. However, this finding does not authorize us to claim that this improvement can be generalized to the full range of neuropsychological and cognitive symptoms characteristic of ASD.
This post aims to provide parents of children with ASD, as well as the patients themselves, with up-to-date and objective information. We rely on methodologically sound research, ensuring that media pressure from certain lobbies with commercial interests does not determine our decision to give probiotics to our children. We also exclude those individual cases presented as success stories that cannot be generalized in any way. In Figure 1, I graphically present my personal opinion about what I believe actually happens when we introduce dietary adjustments in patients with ASD, especially considering the high prevalence of irregular eating behaviors in these patients.
Prebiotics and probiotics
La International Scientific Association for Probiotics and Prebiotics define the prebiotics such as substrates that are selectively used by the host's microorganisms and that would benefit its health. For example, non-digestible carbohydrates.
The probiotics These are live microorganisms that, when administered in adequate amounts, produce a health benefit in the host. Their usefulness has been demonstrated in the treatment of diarrheal episodes and irritable bowel syndrome. Although some research suggests they may improve depressive and anxiety symptoms, my opinion is that the psychological improvements result from the improvement in intestinal function and not from a direct action on the brain via the gut-brain axis.
Gut microbiota and patients with ASD
Findings:
- There is a higher incidence of gastrointestinal disorders in patients with ASD, likely due to the greater recurrence of feeding difficulties. These difficulties are thought to be the cause of intestinal dysbiosis.
- In fact, many patients have been found to have a gut microbiota that differs from control subjects, exhibiting a higher concentration of Clostridium, Lactobacilli, and Desulfovibrio bacteria. Similarly, a reduced ratio of Bacteroides to Firmicutes bacteria has been observed.
- The dysbiosis found in patients with ASD is similar to that which usually occurs when we administer antibiotics for a prolonged period.
- Dysbacteriosis in general not only affects transit and motility, but also the quality of the permeability of the intestinal wall.
Systematic literature review by Qin Xiang Ng et al (May 2019)1
We are highlighting this review because it has two characteristics that we believe are important. First, because it is the most recent publication, and second, because we consider it to be of high quality.
These researchers, after consulting the most important databases, found 1.592 publications, of which 841 were duplicates. Of the remaining 751, 580 were discarded because they were abstracts, conference papers, case studies, letters to the editor, or reviews, and 119 because they involved animal research. Of the remaining 52, 39 had to be eliminated because they did not refer to cases of autism, and 5 because they did not specifically study supplementation with pre- or probiotics. Therefore, only the following were included: 8 publications out of the 1592 initially selected.
Prebiotics
Two randomized, double-blind, placebo-controlled trials were found. The first (Grimaldi, 2018) used maltodextrin. It only produced gastrointestinal improvements; there were no behavioral improvements. The second (Sanectuary, 2019) used bovine colostrum and produced improvements in gastrointestinal problems. Significant improvements were also found in irritability and stereotypies. According to the researchers, the improvements in irritability and stereotypic movements were due to a reduction in IL-13 (Interleukin) and TNF-alpha (Tumor Necrosis Factor) production.
Probiotics
Six articles are cited, two of which were randomized and double-blind. We will only discuss the results of these last two. The first (Parracho, 2010) used Lactobacillus plantarum for three weeks in a sample of 39 children. No improvements were found in either gastrointestinal or behavioral abnormalities. The second (Slykerman, 2018) used Lactobacillus rhammosus, Bifidobacterium animalis, and Bifidobacterium lactis in a sample of 342 children from birth to two years of age. Behavioral worsening was observed.
It is interesting to note that only non-blinded studies report behavioral improvements with probiotics, so their findings of behavioral improvements cannot be conclusive.
Conclusion
There is no scientific evidence that prebiotics and probiotics produce improvements in the symptoms of autism.. It is also true that patients with ASD who have gastrointestinal abnormalities due to eating disorders could, at least empirically, benefit. Therefore, these researchers recommend the need to develop randomized, double-blind studies with representative samples and longer follow-up periods before definitively abandoning this line of research.
