1 OCT 2026 — A study of cancer patients published in Nature on 30 September linked eating sweets during antibiotic treatment to greater damage to the gut's bacteria. Mouse experiments pointed the same way. The researchers stop short of telling everyone on antibiotics to avoid sugar, but say the idea should be tested in trials.
The patients and the meals
The team, from Memorial Sloan Kettering Cancer Center, NYU Langone and City of Hope, followed 173 people in hospital for a haematopoietic cell transplant, a stem cell or bone marrow transplant used mainly for blood cancers. They recorded 9,419 meals, item by item, and collected stool samples to track the bacteria in each patient's gut.
These patients are useful to study because they take heavy courses of antibiotics, and their gut bacteria can collapse as a result, sometimes leaving a single species dominant. The daily meal records and stool samples let the team match what each patient ate against how their bacteria changed.
What they found
Among 158 patients with repeated samples, eating more sweets and sugars during antibiotic treatment predicted a sharper loss of bacterial diversity and a larger bloom of Enterococcus, the paper reports. It calls Enterococcus a pathobiont: a normally resident bacterium that can cause disease when it overgrows.
City of Hope, one of the institutions involved, put the effect at a 24% drop in diversity for every extra 100 grams of sweets, roughly the sugar in a large milkshake. Intake of most food groups fell during the hospital stay, but not the "sugars, sweets and beverages" group, the paper notes.
The mouse experiments
In mice, extra sucrose (ordinary table sugar) made antibiotic-driven Enterococcus growth larger and longer-lasting. The sugar did not reduce how much the mice ate, which rules out one obvious alternative explanation.
What it does not show
The human data are observational. People who eat more sweets in hospital may differ in other ways, and the authors note that outside food was not fully recorded. They call for prospective trials to test whether cutting sugar during antibiotic treatment improves outcomes.
These were also a special group on intensive treatment. The study did not test healthy people on short antibiotic courses.
What the researchers advise
"It's premature to recommend everyone taking antibiotics avoid sugar," Marcel van den Brink of City of Hope, a co-senior author, said in the institution's release. He added that there is "no harm in limiting sugar in your diet".
For hospitals, the practical question sits in the food they hand out. "Many of the foods and drinks we encourage hospitalized patients to consume, like nutritional shakes, smoothies and sports drinks, are high in sugar content," van den Brink said. A commentary in Nature accompanies the paper.
View author profile → · Editorial policy
