The microbiota

The indigenous microbiota is essential. The relationship you maintain with it is usually mutualistic, since your microorganisms provide you with a series of advantages that range from protection against invasion by pathogens and the development of the immune system, to collaboration in the digestion of components of the diet. , the provision of vitamins and other essential nutrients or neurological development in the early stages of life.

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You have a peculiar microbial community that depends on your genotype and early exposure to microorganisms in your environment. This implies that colonization from birth will be different in each individual and that it will depend on factors such as the type of delivery, the lactation model, the rural or urban environment, the use of antibiotics, especially in early childhood, etc. An inadequate development of your intestinal microbiota during the first months of life (either due to the increase in the number of cesarean sections, premature abandonment of breastfeeding or other causes) or, already in adulthood, due to the abuse of antibiotics, a Inadequate diet or the aging process can lead to a state of dysbiosis with an alteration of the microbiota, both qualitative (predominance of species other than the usual ones) and quantitative (lower concentration of beneficial bacteria) .

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The consequence will be the reduction of its healthy effects and the appearance of diseases of all kinds: digestive, gynecological, allergic, dermatological, metabolic, etc. In fact, more than a hundred pathologies have been described that could be related to dysbiosis. In recent years, many diseases in the field of mental health have been linked to an alteration of the microbiota-gut-brain axis. Modulation of the microbiota through dietary intervention or the use of probiotics and prebiotics has become an emerging therapeutic and preventive strategy for many of these disorders.

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The microbiota-gut-brain axis
The microbiota-gut-brain axis is a recognized two-way communication pathway.

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​​​​​​​​​​​​​​Stress can alter gastrointestinal functions (cramps before an exam), while sensations from the digestive system can also affect emotions (a good meal, for example) . The communication of the gut microbiome and the brain takes place through multiple pathways including the vagus nerve, neuropeptides secreted in the gut, cytokines, tryptophan, and metabolites such as short-chain fatty acids. On the other hand, the brain also modulates intestinal microbial responses through the secretion of signaling molecules into the intestinal interior. In this way, the important role that the microbiota would have in the functioning of the central nervous system has been postulated, both in health and disease conditions, at the level of brain development, of the hypothalamic-pituitary-adrenal axis, in the expression of receptors of serotonin and in the turnover of neurotransmitters that regulate the development and function of neuronal synapses.

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Thus, the intestinal microbiota could influence the development of psychiatric and neurological disorders, including behavioral disorders such as autism. As the microbiota plays an important role in brain neurodevelopment early in life, this fact may have its consequences at later ages. In fact, dysbiosis could contribute to neurodevelopmental disorders and mental illnesses in later ages. Different factors, as diverse as diet, genotype, antibiotic consumption or probiotic intake, can shift the balance between homeostasis / dysbiosis of the gut microbiota and affect brain function.

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Microbiota and autism
Several studies describe alterations in the intestinal microbiota of patients with autism spectrum disorders when compared with controls. The bacterial profile reveals a greater abundance of bacteria of the genus Clostridium with a decrease in the ratio of bacteroidetes / firmicutes and an increase in Lactobacillus and Desulfovibrio species, which correlates with the severity of autism. This is also related to a reduction in short chain fatty acids that are modulated by intestinal microorganisms. Together, these studies suggest that autism spectrum disorders are associated with altered composition and function of the gut microbiota.

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Probiotics and autism
Among all the therapeutic approaches to autism, the potential utility of probiotics has been strengthened in recent years. Recent meta-analyzes have concluded that there are studies showing improvement in both gastrointestinal symptoms and behavior.  

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In summary, the use of probiotics with scientific evidence in these patients has brought with it many expectations, both for health professionals and for their families, since one of the main objectives in these children is to improve their quality of life.