A new study published in Nature has identified a link between a common dietary nutrient, gut bacteria, and the immune system. The research suggests that certain gut bacteria can convert choline from food into a chemical messenger that strengthens the gut’s immune defenses.
The study, conducted by researchers, used a specialized screening tool to test how chemicals produced by gut bacteria interact with over 300 different receptors in the body. The team screened 100 different gut bacterial strains, comparing their behavior in a lab dish versus inside living mice.
A key finding was that inside the body, bacteria had access to dietary nutrients, including choline, that are not present in standard lab conditions. This allowed the bacteria to produce a chemical messenger called acetylcholine (ACh). ACh is normally used by the body for nerve signaling, muscle movement, and memory.
Two bacterial strains were studied closely: Bifidobacterium breve, a species common in the gut during early life, and Pediococcus pentosaceus, a probiotic strain found in fermented foods. Researchers identified the bacterial enzymes responsible for converting choline into ACh and created a modified version of B. breve that could not produce ACh for comparison.
The conversion of choline into ACh only happened inside a living body. When the bacteria were grown in standard lab conditions without dietary choline, they did not produce ACh.
When mice were given ACh-producing B. breve, researchers observed three changes. Levels of intestinal IgA, an antibody that coats the gut lining as a first defense against pathogens, increased. The overall makeup of the gut microbiome shifted. Mice with ACh-producing bacteria also showed greater resistance to gut infection.
The study describes this as a direct diet-microbiome-host connection: dietary choline feeds bacteria that produce ACh, which in turn strengthens the gut’s immune defenses. The intestinal lining is constantly exposed to food, bacteria, and potential pathogens. IgA patrols this environment, distinguishing harmless microbes from threats. When IgA levels are strong, the gut is better equipped to stop pathogens.
This 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.
Dietary sources of choline
Choline is found in a variety of foods. Eggs, particularly the yolk, are a reliable source. Liver, legumes, and salmon also contain choline. The ACh-producing strains identified in the study, including Bifidobacterium breve, thrive when a person eats a fiber-rich diet. Pediococcus strains are found in fermented foods like kimchi, sauerkraut, and certain fermented dairy products.
The choline consumed does not only support the body’s own nerve signaling. It also fuels a microbial pathway that shapes immune defenses from the inside out. Eating choline-rich foods regularly and supporting microbiome diversity are two direct ways to help keep that system running.
