Sugary foods and drinks during antibiotics further damaged gut bacteria in transplant patients
Sugar-rich foods exacerbate antibiotic-induced microbiome disruption
Nature, 30 Sept 2026, https://doi.org/10.1038/s41586-026-11077-3
Summary by Claude Opus 5.5 - October 2026
Bottom line: Among very sick hospital patients, sugary foods and drinks consumed while on broad-spectrum antibiotics were linked to extra damage to the gut microbiome: lower bacterial diversity and more overgrowth of Enterococcus, a hospital pathogen. Sugar without antibiotics showed no such link. Mouse experiments support cause and effect.
Study: Peer-reviewed prospective observational cohort, plus mouse experiments. 173 adults hospitalized for allogeneic stem-cell (bone marrow) transplant at Memorial Sloan Kettering, New York, 2017–2022. Every meal tray was tracked (9,419 meals) and 1,009 stool samples from 158 patients were sequenced. Vitamin D was not measured or discussed.
Key findings
- Each extra 100 g (dry weight) of "sugars, sweets and beverages" in the 2 days before a stool sample, while on broad-spectrum antibiotics, predicted an additional 24.1% drop in gut diversity (95% CI 7.7–38.1%).
- The biggest contributors were sports drinks, sugary nutritional shakes and added (rather than naturally occurring) sugars.
This is notable because sugar-rich oral supplements are commonly recommended to transplant patients. - Among patients with above-median sugar intake, each extra day of broad-spectrum antibiotics was linked to about 12% higher death risk (HR 1.12, 95% CI 1.01–1.23). There was no significant link in the lower-sugar half (HR 1.07).
- In antibiotic-treated mice, added sucrose raised Enterococcus 16-fold at day 3 and 33-fold at day 6. Glucose, fructose and fruit smoothie acted similarly. Sucrose alone, without antibiotics, had no effect.
The authors conclude that "limiting sugar intake during antibiotic therapy may help mitigate microbiome injury."
What this does NOT show
- That sugar causes the gut damage in people.
The human data are associations; the cause-and-effect evidence comes from mice. - That it applies to healthy people taking a routine antibiotic. These were severely ill transplant patients on chemotherapy and powerful IV antibiotics.
- That cutting sugar improves survival. No diet trial has been done, the mortality analysis was not adjusted for multiple comparisons, and the high-sugar group also ate less food overall.
- That illness severity is ruled out. Sicker patients get more antibiotics and may favor sweet drinks because of mouth sores and nausea.. The authors' sensitivity analyses reduce this confounding but cannot remove it.
- Gut diversity and Enterococcus are surrogate markers, not health outcomes.
- Several authors have financial ties to microbiome-therapy companies