A study published in Nature found that consuming sugar-rich foods during antibiotic treatment worsens gut microbiome disruption, with an additional 21% reduction in bacterial diversity for every 100-gram increase in sugar, according to research tracking 173 cancer patients undergoing stem cell transplants. The study, conducted by teams at City of Hope, NYU’s Grossman School of Medicine, and Memorial Sloan Kettering Cancer Center (MSK), analyzed 9,419 meals and 1,000 stool samples from patients receiving antibiotics during hematopoietic cell transplants. Patients who consumed more sugar experienced a loss of microbiome diversity as aggressive microbes crowded out other strains of bacteria, linked to an overgrowth of harmful bacteria like Enterococcus, which increases infection risks.
The research, detailed in a press release dated September 30, 2026, by City of Hope, a nonprofit cancer and diabetes research and treatment center, focused on blood cancer patients undergoing allogeneic hematopoietic cell transplants, a high-risk population for severe gut microbiome disruption. Dr. Marcel van den Brink, president of City of Hope Los Angeles and City of Hope chief physician executive, emphasized that antibiotics disrupt the diversity of our gut bacteria. The study’s findings suggest that avoiding sugary foods during treatment may protect the microbiome. Our research supports emerging evidence that avoiding sugary foods during antibiotic treatment may protect the microbiome. Preserving microbiome diversity has previously been linked with improved clinical outcomes for patients with cancer,
said Dr. van den Brink.
Mouse experiments reinforced the human study’s conclusions. When given broad-spectrum antibiotics and feeding them a range of diets, mice that ate a high-sucrose diet quickly developed an overgrowth of Enterococcus in their guts. This pattern mirrored the human data, showing sugar’s role in accelerating microbiome collapse. The study also tracked dietary intake through hospital meal trays and questionnaires, providing more accurate data than traditional memory-based surveys. Researchers noted that the gut microbiome—comprising trillions of microorganisms—plays an essential role in supporting our immune systems and overall health.
Antibiotics are known to broadly destroy good bacteria in the gut, allowing the overgrowth of harmful microbes.
Study Suggests Skipping Sweets During Antibiotic Treatment May Help
The study’s human component involved 173 hospitalized patients, with researchers from City of Hope, Memorial Sloan Kettering Cancer Center, and NYU’s Grossman School of Medicine collaborating. The findings highlight the importance of diet during antibiotic use, particularly for cancer patients undergoing intensive treatments. While the study focused on stem cell transplant recipients, the principles may apply broadly. Our research supports emerging evidence that avoiding sugary foods during antibiotic treatment may protect the microbiome,
van den Brink said. The team says the findings connect to the idea of food as medicine
during cancer care and the ways diet can help people prevent and recover from illness.
A separate cohort study at Memorial Sloan Kettering Cancer Center, conducted between 2017 and 2022, examined adult allo-HCT recipients. Patients were invited to participate in dietary-intake collection three times weekly. Neutrophil engraftment was defined as the first of 3 days of neutrophil count ≥500 per μl. Five patients died without achieving engraftment and were excluded from the analysis of median time to engraftment. No patients were lost to follow-up. For mortality analysis, one patient died before landmark day 12 and was excluded. The latest follow-up/data collection date was in April 2023.
The study's results highlight the need for further research into dietary strategies to mitigate antibiotic-related microbiome damage. Researchers advise patients taking antibiotics to limit sugary foods, though the study does not recommend specific dietary changes. The research could lead to new treatment strategies for cancer patients and potentially others taking antibiotics.