American researchers tracking thousands of hospital meals discovered that consuming high amounts of sugar during antibiotic treatment significantly increases gut microbiome disruption, fueling the growth of potentially harmful bacteria like Enterococcus faecium.
When patients take antibiotics to clear an infection, the drugs do not discriminate between the dangerous pathogens causing illness and the beneficial microbes residing in the digestive tract. A new study published in Nature reveals that what a person eats during this vulnerable window matters immensely. Researchers found that dietary sugar acts as an accelerator for microbial damage, altering the competitive environment inside the gut.
Tracking Hospitalized Patients and Their Meals
The investigation focused on individuals undergoing treatment for blood cancers, a patient group that frequently requires intensive antibiotics and allows for precise dietary monitoring during hospital stays. Investigators from NYU Langone Health, City of Hope, and Memorial Sloan Kettering closely watched 9,419 meals consumed by 173 hospitalized cancer patients while tracking daily changes in their intestinal ecosystems.
By applying Bayesian inference to longitudinal microbiome samples gathered from 158 of those patients, the team identified a clear mathematical link between sweet foods and microbial imbalance. For every additional 100 grams of sugar eaten in the 48 hours leading up to treatment, researchers observed a 21% drop in alpha diversity—the metric used to measure the variety of helpful bacterial species remaining in the gut.
How Dietary Sugar Feeds Harmful Bacteria
The biological mechanism behind the disruption relates to how gut microbes compete for scarce resources. When antibiotics wipe out large portions of the resident flora, surviving bacteria that can rapidly consume simple sugars gain a massive competitive advantage over other species.
Photo: Techno-Science
The findings showed that sugary diets paired with antibiotic administration strongly favored the expansion of Enterococcus faecium, a bacterial species notorious for causing infections that prove difficult to treat in clinical settings. Controlled experiments in mice mirrored the human data. Animals given the antibiotic biapenem alongside dietary sucrose experienced a 16.3-fold increase in their gut Enterococcus population by the third day, surging to a 33.4-fold increase by day six.
The new work identifies dietary sugars as an amplifier of antibiotic-induced microbiome disruption, probably because the potentially harmful bacteria that survive the antibiotics are benefiting from the dietary sugars they can use to expand.
William Jogia, PhD student in Schluter’s lab in the Institute for Systems Genetics, via Juta MedicalBrief
Researchers noted that while the data clearly points to simple sugars as a driver of injury, further work is required to determine whether sugar directly supports Enterococcus growth, weakens competing microbes through an alternative pathway, or triggers a different mechanism altogether within human patients.
Clinical Implications for Vulnerable Cancer Patients
Maintaining a healthy, diverse gut microbiome carries profound weight for patients undergoing intensive medical procedures such as bone marrow transplantation. Prolonged hospital stays for stem cell therapy often coincide with heavy chemotherapy and antibiotic regimens, leaving patients vulnerable when opportunistic pathogens take over a depleted digestive tract.
Photo: nature.com
For patients undergoing intensive treatments like bone marrow transplantation, the healthy diversity of the gut microbiome can have important implications for outcomes. Studies like this help us better understand how everyday factors, including diet, may affect a delicate balance that influences how patients respond to treatment, recover, and experience side effects.
New Study Reveals How Sugar Can Worsen Antibiotic-Related Gut Damage
Marcel van den Brink, MD, PhD, chief physician executive at City of Hope, via Juta MedicalBrief
The research team recommends temporarily cutting back on sweets during and after antibiotic courses to help limit unintended collateral damage to the microbiome.
As we are learning how collateral damage of antibiotics to the microbiome is linked to long-term health problems, it’s important to identify factors that limit these unintended health risks.
Jonas Schluter, assistant professor in the Department of Microbiology at NYU Langone, via Juta MedicalBrief
The next phase of investigation will involve designing controlled clinical trials to test whether short-term dietary interventions can actively improve recovery trajectories and patient outcomes in independent cohorts.
