After birth, the gut becomes colonized by unique bacteria that play a key role in producing the neurotransmitter serotonin. This process helps educate gut immune cells and prevents allergic reactions to food and the bacteria themselves in early development, according to researchers at Weill Cornell Medicine.
The findings of a preclinical study, which were published in Science Immunology on Mar. 15, revealed that bacteria present in the gut of newborns are responsible for producing serotonin. This neurotransmitter, in turn, supports the development of T-regulatory cells (Tregs), which are essential in regulating immune responses to avoid autoimmune diseases and harmful allergic reactions to food or gut microbes.
The Significance of Gut Bacteria in Infants
During the study, researchers noticed significantly higher levels of neurotransmitters, including serotonin, in the guts of neonatal mice compared to adult mice. Dr. Melody Zeng, the senior author of the study, emphasized that while serotonin is commonly associated with brain health, its effects are felt throughout the body due to the presence of neurotransmitter receptors in various tissues.
Dr. Zeng further explained, “The gut plays a crucial role in neurotransmitter production, as it generates more than 90 percent of neurotransmitters in the human body. Our research has shown that serotonin production in the gut, especially in infants, is primarily driven by bacteria present in the gut environment.”
Confirmation of these findings was obtained through samples from a human infant stool biobank established by the Zeng lab in collaboration with the Neonatal Intensive Care Unit at NewYork-Presbyterian Alexandra Cohen Hospital for Women and Newborns. These samples, collected with parental consent and anonymity, provided insight into the role of gut bacteria in newborns.
Role of Gut Bacteria in Serotonin Production
The study’s lead author, Dr. Katherine Sanidad, highlighted that gut bacteria not only produce serotonin directly but also inhibit an enzyme that breaks down serotonin, leading to higher serotonin levels in the gut. This increase in serotonin levels promotes the development of Tregs, which play a crucial role in preventing immune overreactions against gut bacteria or food components.
According to Dr. Sanidad, the presence of serotonin-producing bacteria in the neonatal gut is essential for maintaining immune balance and preventing excessive immune responses during early development.
Long-Term Implications of a Healthy Immune System
Dr. Zeng emphasized the importance of early exposure to beneficial bacteria after birth. Factors such as antibiotic use, limited microbial exposure, and diets in developed countries may impact the abundance of serotonin-producing bacteria in the gut, potentially affecting immune system regulation in infants.
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