A groundbreaking study has revealed that white sugar doesn’t just feed the bacteria in your gut – it rewires them. Researchers have discovered that consuming sugar can trigger physical flips in bacterial DNA, setting off a chain reaction that alters immune responses and gut health. It’s a finding that adds new weight to concerns about sugar’s hidden impacts – and opens the door to a new understanding of how diet directly shapes disease risk at the molecular level.
Scientists at the Technion-Israel Institute of Technology investigated how dietary components – in this case, white sugar – could change the genetic behavior of gut bacteria, and what the potential health impacts of this could be. Their focus was on one species in particular – Bacteroides thetaiotaomicron, a dominant species in the microbiome that helps regulate inflammation, preserve the gut lining, digest complex carbohydrates and protect against pathogens.
Looking first at cell culture and then mice, and finally humans, the researchers found that dietary refined sugar had a strange impact on B. thetaiotaomicron, causing it to undergo DNA inversion – a type of phase variation that sees sections of its genetic code flip direction. And it wasn’t a mutation but a temporary “costume change” that allowed the bacteria to alter what genes it switched on and off. These genes mostly coded for surface-layer proteins, essentially enabling the bacteria to change up its appearance – but this also altered its normally beneficial gut roles.
Phase variation like this is normally seen in pathogens like Salmonella and E. coli to dodge interception by immune cells or antibiotics. For this good bacteria, it’s induced by refined white sugar.
This sugar-triggered microbial disguise also changed how the immune system “saw” the friendly locals and responded. While not demonstrated in the human stool samples that unlocked this DNA inversion mystery, a different outer appearance of B. thetaiotaomicron could trigger the immune system to perceive the bacteria as a threatening foreigner and mount an attack, heightening the risk of inflammation and gut lining damage.
In the study, the researchers found that consuming sugary carbonated drinks that contain white sugar can trigger this DNA inversion. They also observed shifts in inflammatory markers, such as cytokines, suggesting a systemic immune response to the shapeshifting bacteria. It’s the first time scientists have observed this microbial gene-switching mechanism triggered by sugar in the human gut.
The good news is that this DNA inversion is temporary, with the bacteria switching back to their normal appearance once the sugar rush is over, however, repeated exposure amplifies this effect and could lead to more serious gut issues and chronic inflammation.
While the study doesn’t prove that sugar is a serious threat to overall gut health, it does reveal how enough of it will coax beneficial bacteria like B. thetaiotaomicron to act like a pathogen, which warrants further study on the long-term impact of this DNA inversion. It could also help develop specific probiotics that suppress the genetic switching, and help guide dietary recommendations for those prone to the kind of gut problems the disguised microbe could trigger or worsen.
“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,” added the researchers.
The study was published in the journal Nature Communications.