Researchers have identified a concerning link between sugary meals and the loss of gut bacterial diversity in patients receiving antibiotics. The study, published Wednesday in the journal Nature, examined cancer patients who were hospitalized, treated with sustained antibiotics, and later underwent stem‑cell transplants.
Study design and patient diet
Unlike most nutrition research that relies on self‑reported food logs, the investigators could track exactly what each patient ate because the participants consumed only hospital‑prepared meals. The cohort comprised 173 patients who together ate more than 9,400 meals, providing over 1,000 stool samples for analysis.
The research team, led by scientists at Memorial Sloan Kettering Cancer Center, NYU Langone Health and City of Hope Cancer Center, used this controlled setting to explore how macronutrients—fat, carbohydrates, fiber—and specific foods such as chicken, apples and chocolate cake affected the gut microbiome during antibiotic treatment.
Impact of sugar on microbial diversity
Across the patient group, a more intensive antibiotic regimen consistently correlated with a greater reduction in microbial diversity. Most food categories showed no significant association with diversity changes, but sweets—defined as sugars, sweetened foods and beverages—behaved differently. For every 3.5‑ounce increase in sugary intake while on antibiotics, the diversity measured in stool samples fell by roughly 24%.
This loss of diversity was accompanied by a surge in the opportunistic bacterium Enterococcus faecium. Normally kept in check by a balanced microbial community, Enterococcus can overgrow when antibiotics wipe out competing species, potentially crossing the gut barrier and causing bloodstream infections or sepsis.
In the context of bone‑marrow transplantation, the researchers noted that Enterococcus expansion can exacerbate graft‑versus‑host disease, a serious complication where donor stem cells attack the recipient’s tissues.
Animal model and clinical outcomes
To confirm the human findings, the team conducted a mouse experiment. A single injection of a broad‑spectrum antibiotic produced a modest rise in Enterococcus levels. When the mice received added sugar after the antibiotic dose, Enterococcus populations increased 16‑fold by day three and 33‑fold by day six, mirroring the human data.
Clinically, patients who consumed more sugar than the cohort average faced a 12% higher risk of mortality after transplantation compared with those who ate less sugar. While the absolute increase is modest, the researchers described it as statistically significant.
Dr. Jonathan Peled, a physician‑scientist at Memorial Sloan Kettering and study author, emphasized that the findings are not derived from a randomized controlled trial. Nevertheless, he suggested that limiting added sugars during antibiotic courses could be a practical measure to protect the microbiome.
External experts echoed the potential implications. Dr. Anthony Maresso of Baylor College of Medicine, who was not involved in the work, called the study “neat” and noted its relevance for hospital infection control, questioning whether dietary policies should be revised for patients on antibiotics.
The authors caution that further research is needed to determine whether the same risk applies to individuals taking antibiotics outside the hospital setting, such as for ear infections. For now, the data support a conservative recommendation: reduce consumption of sugary foods while undergoing antibiotic therapy, especially for patients undergoing intensive treatments like stem‑cell transplantation.
Mitchell Landsberg is a Senior Technology Correspondent at News Raise. He covers consumer electronics, artificial intelligence, software developments, and digital privacy trends.
