A new study published in Nature has found a link between a common dietary nutrient, gut bacteria, and the immune system. The research shows that certain gut bacteria can turn choline, a nutrient found in foods like eggs, into a chemical messenger that may strengthen the gut’s defenses.
Scientists have long studied how gut bacteria affect health. This study, however, looked at how bacteria behave inside a living body, not just in a lab dish. The researchers used a tool that could test how chemicals from bacteria interact with over 300 different receptors in the body at once. They screened 100 different gut bacterial strains, comparing what each produced in a lab setting versus inside living mice.
The key difference was that inside the body, the bacteria had access to dietary nutrients, including choline, that are not present in standard lab conditions. The study focused on two bacterial strains: Bifidobacterium breve, a species common in early life, and Pediococcus pentosaceus, a probiotic found in fermented foods. Researchers identified the specific bacterial enzymes that convert choline into acetylcholine, or ACh, a chemical messenger used by the body for nerve signaling and muscle movement.
Bacterial ACh and Gut Immunity
When the bacteria had access to dietary choline, they produced ACh. This conversion did not happen when the bacteria were grown in standard lab conditions without choline. To test the effects, the researchers created a modified version of B. breve that could not produce ACh. They then compared mice colonized with the ACh-producing bacteria to mice with the modified strain.
Mice with the ACh-producing bacteria showed higher levels of intestinal IgA, an antibody that coats the gut lining and acts as a first line of defense against pathogens. The study also found that the overall makeup of the gut microbiome shifted, and the mice showed greater resistance to gut infection. The researchers describe this as a direct diet-microbiome-host connection: the choline you eat feeds bacteria that produce ACh, and that ACh strengthens the gut’s immune defenses.
The intestinal lining is constantly exposed to food, bacteria, and potential pathogens. IgA helps patrol this environment, distinguishing between harmless microbes and threats. The finding that bacterial ACh production boosts IgA adds a new layer to understanding the microbiome’s role in immune health.
Diet and the Gut Microbiome
The research was conducted in mice, and more work is needed to confirm how these findings apply to humans. However, the mechanisms identified, including the specific bacterial enzymes and the outcomes related to IgA and infection resistance, make the findings meaningful at this stage. The study suggests that eating choline-rich foods regularly and supporting microbiome diversity are two direct ways to support this system.
Choline is found in foods such as eggs, especially the yolk, liver, legumes, and salmon. The ACh-producing strains identified in the study, including Bifidobacterium breve, thrive when the diet is rich in fiber. Pediococcus strains are found in fermented foods like kimchi, sauerkraut, and certain fermented dairy products.
The study was published in Nature and can be accessed online.
