Sweetened soft drinks don’t just feed your cravings, they may also rewire your gut.
A new study from the Technion-Israel Institute of Technology shows that white sugar in soft drinks can flip genetic switches in gut bacteria, altering their immune-modulating behavior. The research, published in Nature Communications, reveals how one bacterial species, Bacteroides thetaiotaomicron, changes its DNA orientation in response to sugar—shifts that affect inflammation markers, gut lining integrity, and T-cell activity.
Sugar Consumption Triggers DNA Flips in Gut Microbes
In humans, mice, and lab cultures, researchers observed how sugar impacts the genetic landscape of B. thetaiotaomicron, a common gut resident. The key mechanism? Reversible DNA inversions—genomic flips that control gene expression. One site, known as PVR2, responded consistently to sugar intake by switching to a reverse orientation, leading to shifts in bacterial surface proteins and immune interactions.
In mice colonized with this bacterium, sugar water caused:
- Increased reverse orientation of the PVR2 gene region within 7 days
- Decreased expression of IL-6 and ZO-1, markers of gut barrier integrity
- Altered proportions of CD8+ memory T-cells in immune tissues
When sugar was removed, the genetic orientation and immune markers returned to baseline—evidence that the effects are reversible.
Dietary Sugars Reprogram Gut-Immune Communication
“Consumption of soft drinks, supplemented with white sugar, alters the DNA of gut bacteria and affects the host immune system,” the authors wrote. “The good news? These effects are reversible.”
In follow-up lab experiments, B. thetaiotaomicron was grown on 190 different carbon sources, including common sugars like fructose, glucose, and sucrose. Conditioned media from sugar-fed bacteria changed how mouse immune cells responded in vitro. Some sugar sources boosted anti-inflammatory IL-10, while others increased pro-inflammatory IL-17 or T-cell activation markers.
Interestingly, many of these effects were not due to well-known short-chain fatty acids, but to specific proteins secreted by the bacteria. Boiling the media weakened the immune effects, pointing to heat-sensitive molecules, likely surface proteins regulated by phase-variable genes.
Protein Fingerprints Link Diet to Bacterial Behavior
One key insight from proteomics: sugar-fed bacteria secreted distinct outer membrane proteins, especially SusC and SusD starch-binding proteins. Many were tied to phase-variable regions in the genome. “These findings suggest that the altered proteins are secreted into the media, mediating the immune effects,” the authors wrote.
Why It Matters
This study highlights the fine-tuned plasticity of gut microbes and their ability to adapt—and influence us—based on what we eat. It also opens the door to personalized nutrition strategies aimed at modulating the microbiome for immune health. As the authors concluded, “By studying the effects of specific dietary components on the immune-modulatory functionality of key members of the gut microbiota, tailored dietary recommendations can be given to human subjects based on their microbiome composition.”
Journal: Nature Communications
DOI: 10.1038/s41467-025-44938-1
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