A new study published in Nature has found a direct link between a common dietary nutrient, gut bacteria, and the immune system. The research shows that certain bacteria in the gut can convert choline, a nutrient found in foods like eggs, into a chemical messenger that strengthens the gut’s immune defenses.
The study, led by researchers who developed a new screening tool, examined how 100 different gut bacterial strains behaved inside living mice, rather than just in a lab dish. They found that when bacteria had access to dietary nutrients, specifically choline, they produced the chemical messenger acetylcholine. This process did not happen when the bacteria were grown in standard lab conditions without choline.
Two bacterial strains were the focus of the study: Bifidobacterium breve, common in early life, and Pediococcus pentosaceus, found in fermented foods. The researchers identified the specific enzymes these bacteria use to turn choline into acetylcholine. They also created a modified version of B. breve that could not produce acetylcholine, which allowed for a direct comparison.
Mice that had the acetylcholine-producing bacteria showed higher levels of intestinal IgA, an antibody that acts as a first line of defense in the gut. These mice also had a different overall makeup of gut bacteria and showed greater resistance to gut infections. The study describes this as a direct connection between diet, the microbiome, and the host’s immune system.
IgA is the antibody that patrols the intestinal lining, distinguishing harmless microbes from harmful pathogens. The finding that bacterial production of acetylcholine boosts IgA levels adds a new layer to understanding how the microbiome affects immune health. The intestinal lining is constantly exposed to food, bacteria, and potential threats, and strong IgA levels help the gut manage this environment.
The research was conducted in mice, and more studies are needed to confirm if the same processes occur in humans. However, the mechanisms identified, including the specific bacterial enzymes and the resulting immune responses, provide a basis for further investigation.
Choline is found in foods such as eggs, particularly the yolk, as well as liver, legumes, and salmon. The bacterial strains that produce acetylcholine, like Bifidobacterium breve, thrive on a diet rich in fiber. Pediococcus strains are present in fermented foods like kimchi, sauerkraut, and certain dairy products. The study suggests that the choline consumed in the diet not only supports the body’s own nerve signaling but also fuels a microbial pathway that shapes immune defenses from within the gut.
