A new study published in Nature on September 30, 2026, reveals that consuming sugar-rich foods while taking antibiotics significantly worsens gut microbiome disruption. Researchers tracking hundreds of hospitalized cancer patients found that every 100-gram increase in sweets consumed in the days surrounding treatment accelerated the loss of helpful bacterial diversity.
Tracking Every Meal in Hospitalized Cancer Patients
They followed patients with blood cancer who were going through an intensive treatment called allogeneic hematopoietic cell transplant (allo-HCT), a group at particularly high risk for severe gut microbiome disruption and associated side effects. Specifically, the cohort study of adult allo-HCT recipients at Memorial Sloan Kettering Cancer Center in New York took place between 2017 and 2022, where eligible participants had been admitted for Allo-HCT. Newly admitted allo-HCT patients received invitations to join dietary-intake monitoring on a tri-weekly basis, with April 2023 marking the final point for follow-up and data gathering. Led by researchers from NYU Langone Health and Memorial Sloan Kettering, the study precisely tracked every food item in meals eaten by hospitalized cancer patients and then measured their gut microbiome changes. By evaluating 1,000 stool specimens alongside a total of 9,419 meals consumed by 173 hospitalized cancer patients—exceeding 9,400 meals overall—the research connected sugary diets to heightened antibiotic-induced microbiome degradation among those undergoing stem cell transplants. Bedside meal trays included a printout generated by the commercial hospital kitchen software Computrition, prompting patients to mark right after eating whether they finished 0, 25%, 50%, 75% or 100% of each ordered food item. These instruments were collected by a dietician or other research staff.
How Sugar Amplifies Antibiotic Damage
Antibiotics are among the most prescribed drugs globally, and are known to eliminate helpful bacteria alongside harmful species, in some cases letting harmful ones dominate. Preserving a robust mix of natural species helps the microbiome better withstand harmful pathogens, whereas antibiotics strip away this variety and leave the intestinal tract more susceptible to illness, according to the researchers. Research from California’s nonprofit cancer and diabetes care and research institution, City of Hope, served as the basis for the findings shared in the journal Nature. The team uncovered a clear, measurable pattern: dietary sugar acts as an accelerator for this collateral damage. Accounting for a 21 percent extra decrease in alpha diversity—which tracks the variety of beneficial bacterial species—each 100-gram rise in pre-treatment sweets over a two-day period, matching the sugar content of a large milkshake, caused bacterial diversity to decline by greater than 20 percent in the study group.
“When someone is going through cancer treatment and not feeling well or eating much, we often advise they drink smoothies, sports drinks, or nutrition shakes, thinking that at least this way they’ll get some fluids, protein, and electrolytes,” as stated by Jonathan “Tsoni” Peled, MD, PhD, a cellular therapist and bone marrow transplant specialist at Memorial Sloan Kettering Cancer Center (MSK). But we have found that when these kinds of sugary foods and drinks are combined with antibiotics, the results can be toxic to the microbiome because they greatly lower the diversity of microorganisms.
Next Steps for Clinical Practice
As we are learning how collateral damage of antibiotics to the microbiome are linked with long-term health problems, it’s important to identify factors that limit these unintended health risks,
said researcher Jonas Schluter, PhD, from NYU Langone Health in New York. Our study, which used more than 9,000 recorded meals, suggests that modifying diet during and after antibiotics, specifically by reducing sweets intake, could help with that.
Readers should consult qualified healthcare professionals regarding personal dietary and medical decisions.
