Summary In recent years, there has been an increase in studies on the implications of gut microbiota (GM) on the behaviour of children with autism spectrum disorders (ASD) due to a dysbiosis in GM that can trigger onset, development or progression of ASD through the microbiota–gut–brain axis. The aim of this study is to carry out a systematic review of articles from the last 6 years that analyse GM in children with ASD compared to GM in control groups. Children with ASD showed a higher abundance of Roseburia and Candida genera, and lower abundance of Dialister, Bilophila, Veillonella, Streptococcus, Coprococcus and Prevotella genera. Those differences can be attributed to factors such as different nationalities, nature of control groups, place where the sample was taken, gastrointestinal (GI) problems or bacterial detection methods. It is still too early to define a specific GM profile of children with ASD, and future studies should focus on homogenizing the characteristics of samples and control groups. Furthermore, new multicentre studies should also focus on the impact of GM on GI physiology, neurophysiology and behaviour of children with ASD, and on performing psychometric analyses of the correlation between the severity of ASD behavioural symptoms and GM profiles.

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During the complementary feeding (CF) period, nutritional imbalances can have negative consequences not only on a child's health in the short term but also later in adulthood, as a phenomenon known as "nutritional programming" takes place. The aim of this study was to evaluate the possible changes in body growth, gut microbiota (GM) and the immune system in mice fed with two different commercial sterilized baby foods in jars (BFJs) for CF. Mice fed with different BFJs (A and B groups) showed an accelerated growth from the fifth week of life when compared with the control (C) group. Group A showed a higher BMI, post-weaning growth rate, and IL-10 levels and a decrease in the Lactobacillus group. Group B showed a significant decrease in the total bacterial count, Lactobacillus group, Enterococcus spp. and Bacteroidetes-Prevotella. The Bifidobacterium genus tended to be lower in groups A and B. Akkermansia muciniphila was more frequently detected in group C. The results obtained from groups A and B can be attributed to the BFJ fatty acid profile, rich in UFAs. This study demonstrates for the first time that the commercial BFJ composition during CF might be a "programming" factor for body growth, GM and the immune system.

La microbiota intestinal humana es el conjunto de microorganismos que habitan de forma simbiótica en el intestino. El establecimiento de la comunidad microbiana intestinal parece ser un proceso escalonado que cubre el primer año de vida. Los factores que afectan a la microbiota intestinal son el nacimiento por cesárea, el no amamantamiento, el medio ambiente, la edad gestacional, la genética del huésped, la exposición a infecciones (maternas e infantes) y el uso de antibióticos. La microbiota intestinal tiene gran influencia en la modulación de la salud y está relacionada con la obesidad y diversas enfermedades mentales tales como trastornos del neurodesarrollo, autismo, Alzheimer y esquizofrenia. Esta influencia se realiza a través del eje microbiota-intestino-cerebro. Los diferentes estudios en este campo revelan cómo las variaciones en la composición de la microbiota intestinal influyen en todos los aspectos de la fisiología, incluyendo la obesidad, la función cerebral y el comportamiento. Aunque la microbiota intestinal característica en la obesidad ha sido estudiada en profundidad, en términos de neurociencia y enfermedad psiquiátrica el campo todavía está en su infancia, pero se están acumulando evidencias de que posee un papel clave.