Researchers Say You Should Avoid This One Food Choice While Taking Antibiotics

Our microbiomes include bacterial species that evolved alongside us, helping with digestion and supporting the immune system. But when antibiotics are used, they often eliminate helpful gut bacteria along with the harmful ones.

According to a new study, eating sugary foods while on antibiotics may make that disruption worse. Researchers from NYU Langone Health, City of Hope, and Memorial Sloan Kettering found that sugar intake combined with antibiotics was linked to a greater drop in gut-microbiome diversity.

That diversity matters: when the gut contains a wide range of natural species, it is better able to resist the growth of dangerous pathogens. Antibiotics reduce that diversity, leaving the gut more vulnerable to disease, the study says.

Microbiome and Antibiotics

In one of the largest and most detailed studies of its kind, researchers tracked every food item in 9,419 meals eaten by 173 hospitalized cancer patients and then measured changes in their gut microbiomes. The team focused on patients with blood cancers because they often receive antibiotics and because their food intake can be closely monitored while in the hospital. For every 100 grams of sugar consumed in the 48 hours before antibiotic treatment, the researchers found an additional 21% drop in bacterial diversity.

The study also found that a diet high in sugar, paired with antibiotic treatment, encouraged blooms of Enterococcus faecium, a bacterium associated with difficult-to-treat infections. Mouse experiments confirmed the pattern: exposure to both an antibiotic and sucrose led to a rise in the Enterococcus population in the gut by day three, and an even larger increase by day six.

Patients with blood cancers who undergo stem cell transplantation are typically hospitalized for several weeks and receive both chemotherapy and antibiotics during that time. Their nutrition can shift dramatically throughout the hospital stay, while their microbiomes are severely damaged. In these patients, harmful bacteria such as Enterococcus faecium can flourish because much of the gut ecosystem has been destroyed.

Dietary Changes to Improve Clinical Outcomes

“The microbiome is emerging as an important factor in cancer care,” said co-senior study author Marcel van den Brink, MD, PhD, chief physician executive at City of Hope. “For patients undergoing intensive treatments such as 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.”