Antibiotics are lifesaving drugs, but they come with collateral damage: they wipe out not only harmful bacteria but also the diverse community of helpful microbes in our gut. Now, a major new study shows that eating sweets while on antibiotics can make that damage significantly worse.
Researchers from NYU Langone Health, City of Hope, and Memorial Sloan Kettering tracked the diets and microbiomes of 173 hospitalized cancer patients and recorded more than 9,400 meals.
They found that for every 100 grams of sugar consumed in the 48 hours before antibiotic treatment, patients experienced an additional 21% reduction in microbiome diversity, a measure of how many different beneficial bacterial species are present.
This loss of diversity makes the gut more vulnerable to harmful bacteria. One species in particular, Enterococcus faecium, flourished under the combination of antibiotics and sugar. In mice, sucrose plus the antibiotic biapenem drove a 16-fold increase in Enterococcus by day 3, and more than 33-fold by day 6.
The gut microbiome has an effect on the body’s ability to fight off disease as well as how effectively treatments for cancer work. If antibiotics upset the balance of the gut microbiome, then harmful bacteria may take over the gut and lead to increased rates of infection and poorer patient outcomes.
“As we are learning how collateral damage from antibiotics to the microbiome is linked with long-term health problems, it’s important to identify factors that limit these unintended health risks,” said Jonas Schluter, PhD, co-senior author. “Our study… suggests that modifying diet during and after antibiotics, specifically by reducing sweets intake, could help with that.”
Patients with blood cancers often undergo stem cell transplants, chemotherapy, and prolonged antibiotic use. Their microbiomes are already fragile.
“The microbiome is emerging as an important factor in cancer care,” said Marcel van den Brink, MD, PhD, co-senior author.
“Healthy diversity of the gut microbiome can have important implications for outcomes.”
Jonathan Peled of Memorial Sloan Kettering added: “Especially in blood cancer patients, microbiome injury is associated with worse outcomes, including higher overall mortality and infections. An important next step will be to design clinical trials to test whether short-term dietary changes can improve clinical outcomes.”
The results show that eating sugary foods acts as an enhancer of the effects of antibiotics. Although it is not known whether sugar is feeding the harmful bacteria such as Enterococcus, reducing competition from other beneficial bacteria, or acting in some other way, what we do know is that limiting sweet items while taking antibiotics may be helpful for protecting the health of your gut.
As co-author William Jogia put it: “While the findings suggest that reducing simple sugars may limit microbiome injury, whether sugar directly supports Enterococcus, weakens competing bacteria, or acts through another mechanism in patients remains to be seen.”
A simple yet significant principle is illustrated by this study; the food you ingest has the potential to influence how your body reacts to medications. The combination of high-sugar intake and antibiotics could prove hazardous to the sensitive equilibrium of the microbiome in your gut.
In addition, the results of our study indicate that if you reduce your intake of simple sugar while on antibiotics, it could potentially prevent loss of some of the beneficial bacteria in your gastrointestinal tract. However, we need to conduct additional research with other populations to see whether our findings hold true for everyone and what types of interventions work best to maintain a healthy gut microbiota.
Journal Reference:
- Dai, A., Ballweg, A., Jogia, W. et al. Sugar-rich foods exacerbate antibiotic-induced microbiome disruption.
Nature (2026). 10.1038/s41586-026-11077-3
