New research suggests that eating more sugar while taking antibiotics may worsen the disruption those drugs cause to the gut microbiome. The study, published in Nature, tracked 9,419 meals from 173 hospitalized blood cancer patients and collected daily microbiome samples. For every additional 100 grams of sugar consumed in the 48 hours before treatment, the researchers observed a 21% greater decline in alpha diversity, a measure of beneficial bacterial variety. Higher sugar intake combined with antibiotics was also linked to increased growth of Enterococcus faecium, a species associated with difficult-to-treat infections.
Mouse experiments produced similar results. Animals given the antibiotic biapenem along with dietary sucrose saw a 16.3-fold increase in gut Enterococcus by day 3, and a 33.4-fold increase by day 6. The researchers suggest that potentially harmful bacteria surviving antibiotic treatment may use dietary sugars to expand, amplifying the microbiome disruption. However, they note that the exact mechanism—whether sugar directly feeds these bacteria or weakens competing species—remains unclear.
The findings point to a simple possible intervention: temporarily reducing sweets during and after antibiotic treatment could limit microbiome damage. The researchers emphasize that clinical trials are still needed to determine whether such dietary changes improve patient outcomes. As one co-author noted, the study highlights how everyday factors like diet may influence a delicate balance that affects how patients respond to treatment and recover.