Yogurt consumption increases the ingestion of probiotic bacteria, in particular Lactobacilli and Bifidobacteria, and may therefore affect the diversity and balance of human gut microbiota. Previous research found that changes in gut microbiota moderate the peripheral and central nervous system, resulting in altered brain functioning, and may have an impact on emotional behavior, such as stress and anxiety.
The described effect suggests the existence of a gut-brain axis. Because of the bidirectional communication between the nervous system and the immune system, the effects of yogurt bacteria on the nervous system cannot be separated from effects on the immune system. Researchers suggest that the communication between gut microbiota and the brain can be influenced by the intake of probiotics, which may reduce the level of anxiety and depression, and affect brain activity that controls emotions and sensations. Autism patients often suffer from gastrointestinal abnormalities, whereby viral infections over pregnancy have an impact on the long term, this might be reversed through consumption of specific bacteria, also found in yogurt.
As the composition of gut microbiota is different for each individual, changes in the balance and content of common gut microbes affect the production of short chain fatty acids butyrate, propionate, and acetate. These fermentation products improve host metabolism by stimulating glucose and energy homeostasis, regulating immune responses and epithelial cell growth, and also supporting the functioning of the central and peripheral nervous systems.