Antibiotics are recognized for causing gastrointestinal issues, particularly diarrhea, as they kill harmful bacteria while also eliminating healthy gut microorganisms. A recent study published in *Nature* on September 30, 2026, suggests that avoiding sugar during antibiotic treatment may protect the gut microbiome from further harm.
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Dr. Jonathan “Tsoni” Peled, a bone marrow transplant specialist at Memorial Sloan Kettering Cancer Center, noted that sugary items such as smoothies and nutrition shakes, often recommended for patients undergoing cancer treatment, could adversely affect microbiome health when combined with antibiotics. He stated that such sugary foods significantly reduce microbial diversity in the gut.
The research stemmed from an ongoing effort at Memorial Sloan Kettering to track the gut microbiomes of patients undergoing stem cell or bone marrow transplants. These patients, whose immune systems are compromised, frequently require antibiotics. Over time, the use of antibiotics can drastically disrupt their gut microbiomes. Dr. Peled pointed out that these patients generally start with a diverse microbiome, but it can be dominated by a single organism, typically Enterococcus, during treatment, leading to increased risks of severe infections.
The study involved 173 hospitalized patients, allowing researchers to monitor their diet precisely through recordings of over 40,000 meals and more than 1,000 fecal samples. The findings revealed a troubling correlation: for every 100-gram increase in sugar consumption—roughly equivalent to two cans of soda—the diversity of the gut microbiome decreased by 24% during antibiotic treatment. This effect persisted even after accounting for the patients’ health conditions.
Indeed, Dr. Peled highlighted that many foods recommended for sick individuals may harm their microbiome due to high sugar content. While this research focused on cancer patients, the implications raise questions about sugar consumption among healthy individuals prescribed antibiotics for milder illnesses. Preliminary studies in mice indicated that a diet high in sugar could exacerbate microbiome disruption caused by antibiotics, suggesting a broader impact.
Dr. Peled emphasized that while concrete recommendations for all antibiotic users are not yet available, avoiding sugar during treatment may be a feasible and low-risk approach to consider.