Autism and Gut Bacteria
This week, we’re discussing the emerging science of the human/bacteria interface. Scientists are beginning to understand how important it is to maintain a healthy balance among the many species of bacteria colonizing the human body. For instance, the human gut contains at least 100 trillion microbial cells. Some experts recommend thinking of these microbes as another organ, capable of affecting our physiology, metabolism, nutrition, and immune function.
Disruption of the delicate balance among types of microbes—by antibiotics, for example—may influence the risk of developing inflammatory bowel disease, or even obesity. And we’ve learned recently that what you eat influences the types of bacteria that thrive in your gut. The upshot is that eating red meat is linked to an increased risk of heart disease because of the activity of bacterial intermediaries living in the gut. Conversely, a mostly vegetarian diet, with plenty of natural fiber, is linked to better overall health, possibly because such a diet helps maintain healthy gut microflora.
Recently, scientists investigated the link between gut microflora and symptoms of gastrointestinal (GI) illnesses among children with autism. In the past, it’s become clear that autistic children suffer from GI complaints more frequently than “normal” children. The investigators wondered if there was a link between autism and the gut microbiota. The simple answer is “yes.” In the study, autistic children had less microbial diversity. Significantly, they had notably less of a particular genus of bacteria, known as Prevotella, than healthy children. These microbes are especially adept at breaking down carbohydrates.
Decreased diversity is problematic, because recent studies indicate greater microbial diversity correlates with a healthier gut that’s less prone to illness. In the present study, investigators were surprised to learn “the presence of autistic symptoms, rather than the severity of GI symptoms, was associated with less diverse gut microbiomes.” So there is a link between autism and gut microbes, but the link remains unclear. The results suggest “a potential influence of unusual diet patterns observed in autistic children.”
De Filippo C, Cavalieri D, Di Paola M, Ramazzotti M, Poullet JB, Massart S, et al. Impact of diet in shaping gut microbiota revealed by a comparative study in children from Europe and rural Africa. Proc Natl Acad Sci U S A. 2010 Aug 17;107(33):14691-6. doi: 10.1073/pnas.1005963107. Epub 2010 Aug 2.
Dae-Wook Kang, Jin Gyoon Park, Zehra Esra Ilhan, Garrick Wallstrom, Joshua LaBaer, James B. Adams, Rosa Krajmalnik-Brown. Reduced Incidence of Prevotella and Other Fermenters in Intestinal Microflora of Autistic Children. PLoS ONE, 2013; 8 (7): e68322 DOI: 10.1371/journal.pone.0068322
Guinane CM, Cotter PD. Role of the gut microbiota in health and chronic gastrointestinal disease: understanding a hidden metabolic organ. Therap Adv Gastroenterol. 2013 Jul;6(4):295-308. doi: 10.1177/1756283X13482996.