Sweets during antibiotics may deepen the damage to gut bacteria

Antibiotics don't only hit the bacteria making you sick. They also thin out the crowded community living in your gut. A new paper in Nature asks whether what you eat while that's happening changes how hard the hit lands.

Researchers tracked 9,419 meals eaten by 173 people in hospital for a stem cell transplant, a treatment usually given for blood cancers. They matched those meals to microbiome samples from 158 of the patients. People who ate more sweets and sugars while on antibiotics showed greater disruption. Their gut communities had fewer kinds of bacteria, and Enterococcus, a bacterium that can cause disease, expanded further.

Meal records can't separate sugar from everything else happening to a very sick person, so the team turned to mice. Adding sucrose, ordinary table sugar, made antibiotic-driven Enterococcus blooms bigger and longer-lasting. According to the press release, each 100 grams of sugar eaten in the 48 hours before antibiotics was linked to an additional 21% drop in bacterial diversity.

That is where the evidence stops. Transplant patients go through intensive treatment and are very different from a healthy adult taking a short course of antibiotics. The human data show an association, and the cause-and-effect evidence comes from mice. The authors say the finding needs checking in independent groups of patients and in studies that actually change what people eat.