Eating high amounts of sugar while taking antibiotics can intensify damage to the gut microbiome, according to a new study published in Nature. Researchers found that for every additional 100 grams of sugar consumed in the 48 hours before treatment, the diversity of beneficial gut bacteria dropped by 21 percent.
The study focused on hospitalized cancer patients with blood disorders. These individuals often receive intensive antibiotic regimens alongside chemotherapy or stem cell transplants. The combination of powerful drugs and dietary sugar created a environment where harmful bacteria could thrive.
Microbiome Diversity Declines With Sugar
The research team tracked 9,419 meals eaten by 173 patients at NYU Langone Health, City of Hope, and Memorial Sloan Kettering. They recorded daily food intake and collected microbiome samples to monitor changes in bacterial populations.
Antibiotics are designed to kill harmful bacteria, but they often destroy beneficial species as well. This loss of diversity leaves the gut ecosystem vulnerable. When the protective microbial community is weakened, potentially dangerous pathogens can take over.
The data showed a clear link between sugar consumption and this vulnerability. Patients who ate more sugar experienced a sharper decline in alpha diversity, a key measure of microbial variety. This decline was not just a side effect of the illness but correlated directly with dietary choices during the treatment window.
Harmful Bacteria Surge
The study also identified a specific bacterial species that flourished under these conditions. Sugary diets combined with antibiotic treatment were associated with significant increases in Enterococcus faecium. This organism is a known cause of hospital-acquired infections that are difficult to treat.
Mouse experiments confirmed the human findings. Animals given the antibiotic biapenem and a diet high in sucrose saw their gut Enterococcus populations explode. By day three, the bacterial load was 16.3 times higher than in control groups. By day six, it was 33.4 times higher.
Researchers believe sugar acts as fuel for these surviving harmful bacteria. While antibiotics reduce the competition from beneficial microbes, the remaining pathogens use dietary sugars to expand rapidly. This process magnifies the injury to the gut lining and increases the risk of systemic infection.
Clinical Implications for Cancer Care
The findings highlight the importance of diet in cancer care. Patients undergoing bone marrow transplants are hospitalized for weeks. Their food intake is closely monitored, making it possible to adjust nutritional strategies.
Jonas Schluter, co-senior author and assistant professor at NYU Langone, emphasized the need to limit unintended health risks. He noted that modifying diet during and after antibiotic courses could help protect the microbiome. Reducing sweets intake is a practical step that patients and hospitals can implement immediately.
Marcel van den Brink, chief physician executive at City of Hope, stated that the microbiome is emerging as a critical factor in treatment outcomes. A healthy gut balance influences how patients recover and experience side effects. Understanding how everyday factors like diet affect this balance is essential for improving care.
Jonathan Peled, associate director at Memorial Sloan Kettering, pointed out that microbiome injury is linked to worse outcomes, including higher mortality rates in blood cancer patients. The next step is to design clinical trials to test whether short-term dietary changes can improve these outcomes.
The research team included authors from multiple institutions, including the University of Texas MD Anderson Cancer Center and the University of Minnesota. Funding was provided by the National Institutes of Health and several private foundations.
While the study establishes a strong correlation between sugar and gut damage, researchers note that more work is needed to determine the exact mechanisms. Whether sugar directly supports Enterococcus or weakens competing bacteria remains to be seen. However, the evidence suggests that cutting back on simple sugars during antibiotic treatment could reduce microbiome injury.
Source: ScienceDaily
