City of Hope Study Links High Sugar Intake to Greater Antibiotic-Related Gut Microbiome Disruption
Researchers at City of Hope, a major cancer research and treatment organization, have reported new findings suggesting that consuming higher amounts of sugar during antibiotic treatment may contribute to disruption of the gut microbiome. The study, published in Nature, examined patients with blood cancers undergoing allogeneic hematopoietic cell transplantation, a population that is particularly vulnerable to significant changes in gut microbial communities and complications associated with microbiome injury.
The research provides new evidence for the potential role of diet in protecting the gut microbiome during intensive cancer treatment. It also highlights how food intake may interact with antibiotics to influence the balance of bacteria living in the gastrointestinal tract.
The findings are relevant to the broader concept of “food as medicine,” in which nutrition is considered an important component of disease prevention, treatment support and recovery. According to the researchers, the results could eventually contribute to new approaches for protecting the microbiome in cancer patients and potentially other people who require antibiotic treatment.
“Antibiotics disrupt the diversity of our gut bacteria, or microbiomes, which play an essential role in supporting our immune systems and overall health,” said Marcel van den Brink, M.D., Ph.D., co-senior author of the study, president of City of Hope Los Angeles and chief physician executive of City of Hope.
“Our research supports emerging evidence that avoiding sugary foods during antibiotic treatment may protect the microbiome. Preserving microbiome diversity has previously been linked with improved clinical outcomes for patients with cancer,” he added.
Van den Brink, who has conducted research in microbiome biology, cell transplantation and cancer immunotherapy, collaborated on the study with Jonathan Peled, M.D., Ph.D., of Memorial Sloan Kettering Cancer Center, and Jonas Schluter, Ph.D., of NYU’s Grossman School of Medicine.
Large-Scale Study Tracks Diet and the Microbiome
The study was conducted over five years and included patients undergoing intensive treatment for blood cancers. These patients were hospitalized for several weeks while receiving chemotherapy, and in some cases radiation, to eliminate their existing immune system before receiving a stem cell transplant.
Because patients undergoing this type of treatment are highly susceptible to infection, antibiotics are commonly used to prevent or treat infections during the hospitalization period.
The researchers noted that antibiotics can have effects beyond eliminating disease-causing bacteria. Broad-spectrum antibiotics can also affect beneficial microorganisms in the gastrointestinal tract, potentially reducing the diversity of the microbiome and allowing certain organisms to expand.
In the study population, every patient received at least one antibiotic during hospitalization, while approximately 80% received one or more broad-spectrum antibiotics. These antibiotics can affect a wide range of bacterial species and therefore have a particularly substantial impact on the gut microbiome.
To investigate the relationship between diet, antibiotic exposure and microbial changes, researchers tracked 9,419 meals consumed by 173 hospitalized patients. They also assessed microbiome diversity through stool samples from 158 patients.
The study generated a detailed dataset that enabled researchers to compare patients’ dietary intake with changes in their gut microbial communities.
Real-Time Dietary Data Provided Detailed Insight
One of the notable aspects of the study was the way dietary information was collected.
Rather than relying primarily on patients to recall what they had eaten days or weeks earlier, the research team worked with the hospital kitchen to track nutritional information for meals served to participants. Each meal tray included a questionnaire that asked patients to record how much of each food and beverage they consumed.
The researchers ultimately recorded information covering more than 40,000 individual food items.
For individual patients, the research team tracked between eight and 128 meals, depending on the patient’s length of participation. The observation period extended from 12 days before transplantation through as many as 49 days following transplantation.
In addition, the researchers analyzed more than 1,000 stool samples to monitor changes in the gut microbiome over the course of treatment.
The high frequency and detailed nature of the dietary information allowed the researchers to examine associations that can be difficult to identify in conventional nutrition studies.
“Unlike past nutrition studies that rely on patients’ memories of what they ate or other imprecise surveys, we had meticulous dietary records collected in real time,” van den Brink said. “This enabled us to look for patterns that otherwise might be impossible to detect.”
Higher Sugar Consumption Associated With Microbiome Diversity Loss
Using multiple statistical models, the researchers analyzed the data for associations between dietary patterns and changes in microbiome diversity.
A consistent association emerged between higher consumption of sweets during antibiotic treatment and reductions in bacterial diversity.
According to the researchers, patients who consumed greater quantities of sweets while receiving antibiotics were more likely to experience a decline in microbiome diversity.
The researchers also identified Enterococcus as an organism of particular interest. Expansion of Enterococcus in the gut can be associated with adverse outcomes in patients undergoing hematopoietic cell transplantation, including bloodstream infections and graft-versus-host disease.
The study found that the combination of broad-spectrum antibiotic exposure and higher intake of sugar-rich foods was associated with greater disruption of the gut bacterial community.
The researchers reported a 24% reduction in bacterial diversity for every 100-gram increase in sweets, with the amount of sugar corresponding approximately to the sugar content of a large milkshake.
The finding does not establish that sugar directly causes the observed microbiome changes in all people taking antibiotics. Rather, the human study identified an association within a particularly vulnerable patient population. Additional clinical research will be needed to determine whether reducing sugar consumption directly prevents microbiome injury.
Mouse Experiments Provide Additional Evidence
To further investigate the relationship between sugar, antibiotics and the microbiome, the researchers conducted experiments in mice.
Healthy mice received broad-spectrum antibiotics and were subsequently fed different diets. Animals receiving a high-sucrose diet while taking antibiotics developed an overgrowth of Enterococcus in their gastrointestinal tracts.
By comparison, mice consuming the high-sugar diet without antibiotics maintained normal bacterial diversity.
The animal findings provided additional support for the association observed in the human patient data. They also gave researchers a potential biological model for investigating how dietary sugar may interact with antibiotic exposure to alter microbial communities.
“The fact that animal studies support associations we found in patient data provides a compelling rationale for future clinical trials to evaluate whether reducing sugar intake during antibiotic use would protect the microbiome,” van den Brink said.
The researchers emphasized that controlled clinical trials will be necessary to determine whether dietary changes can directly preserve microbiome diversity and whether such changes can improve clinical outcomes.
Potential Importance for Cancer Care
The gut microbiome has increasingly become an area of interest in cancer research. Gut bacteria interact with the immune system and can influence the biological environment in which cancer treatments are administered.
For patients undergoing hematopoietic cell transplantation, microbiome disruption can be particularly important because these individuals experience profound changes to their immune systems and are exposed to intensive treatments and antibiotics.
“The microbiome is emerging as an important factor in cancer care,” van den Brink said. “The better we understand what supports and disrupts it, the more opportunities we have to reduce treatment side effects while improving how patients respond to and recover from therapy.”
The findings also highlight nutrition as a potentially modifiable factor during hospitalization. Many patients receive nutritional products and beverages as part of supportive care, including shakes, smoothies and sports drinks. Some of these products can contain substantial amounts of added sugar.
“Many of the foods and drinks we encourage hospitalized patients to consume, like nutritional shakes, smoothies and sports drinks, are high in sugar content,” van den Brink said. “That’s something we’ll need to evaluate when prescribing antibiotics.”
However, the researchers caution against interpreting the findings as a universal recommendation for everyone taking antibiotics to eliminate sugar from their diet.
Antibiotic Stewardship and the Microbiome
The study also adds another dimension to the concept of antibiotic stewardship.
Antibiotic stewardship programs generally focus on using antibiotics appropriately to reduce unnecessary exposure and slow the development of antibiotic resistance. The City of Hope researchers suggest that the effects of antibiotic selection on the microbiome may also deserve consideration.
“Antibiotic stewardship includes thinking about how different antibiotics affect the microbiome,” van den Brink said. “Our study demonstrates that some antibiotics disrupt beneficial gut bacteria more than others.”
For patients, the researchers suggest discussing antibiotic selection with their healthcare teams and considering whether equally effective treatment options may have different effects on the microbiome.
Such decisions, however, need to be made in the context of the individual patient’s infection, medical condition and treatment requirements. Patients should not stop or alter prescribed antibiotics without guidance from their healthcare providers.
Is Avoiding Sugar During Antibiotic Treatment Recommended?
Despite the findings, van den Brink said it is too early to recommend that everyone taking antibiotics avoid sugar.
“It’s premature to recommend everyone taking antibiotics avoid sugar,” he said.
The study also raises questions about the effectiveness of other commonly used strategies for maintaining microbiome health. For example, many people use probiotics while taking antibiotics, but the researchers noted that there is not strong evidence establishing that probiotics preserve or restore microbiome diversity in this context.
The researchers said reducing sugar intake is nevertheless a potentially straightforward dietary change that could be investigated further.
The distinction is important because the current findings come from a specific patient population undergoing intensive cancer treatment. The effects observed in these patients may not necessarily apply in the same way to healthy individuals taking short courses of antibiotics for common infections.
Future clinical trials will be needed to establish whether reducing dietary sugar directly protects the microbiome and whether such protection translates into better health outcomes.
Advancing Microbiome Research at City of Hope
The findings build on City of Hope’s broader research into the relationship between cancer, nutrition, immunity and the microbiome.
The organization’s Microbiome Program is investigating how the microorganisms living in the human body interact with cancer biology and treatment. Its research incorporates areas including diet, nutrition and immune function, with the goal of identifying approaches that could support personalized cancer care.
The new study contributes to this research by examining diet as a potentially important factor influencing microbiome health during intensive treatment.
The study, titled “Sugar-rich foods exacerbate antibiotic-induced microbiome injury,” was supported by funding from the National Cancer Institute, National Heart, Lung, and Blood Institute, and the Susan and Peter Solomon Microbiome, Nutrition and Cancer Program at Memorial Sloan Kettering Cancer Center.
The researchers emphasized that the study findings provide a basis for further investigation rather than a definitive dietary prescription.
Overall, the research adds to growing evidence that the microbiome is closely connected with cancer treatment and that factors outside of drugs themselves—including diet and antibiotic selection—may influence microbial health. By combining detailed real-time dietary tracking with extensive microbiome sampling and supporting animal experiments, the researchers have identified a potential relationship between sugar-rich foods and antibiotic-associated microbiome disruption.
Further clinical studies will determine whether reducing sugar intake can preserve microbiome diversity and ultimately improve outcomes for patients receiving antibiotics, particularly those undergoing intensive cancer therapies such as hematopoietic cell transplantation.
About City of Hope
City of Hope’s mission is to make hope a reality for all touched by cancer and diabetes. Founded in 1913, City of Hope has grown into one of the largest and most advanced cancer research and treatment organizations in the United States, and one of the leading research centers for diabetes and other life-threatening illnesses. City of Hope research has been the basis for numerous breakthrough cancer medicines, as well as human synthetic insulin and monoclonal antibodies.
With an independent, National Cancer Institute-designated comprehensive cancer center that is ranked among the nation’s top cancer centers by U.S. News & World Report at its core, City of Hope’s uniquely integrated model spans cancer care, research and development, academics and training, and a broad philanthropy program that powers its work. City of Hope’s growing national system includes its Los Angeles campus, Orange County, California, campus, a network of clinical care locations across Southern California and cancer treatment centers and outpatient facilities in the Atlanta, Chicago and Phoenix areas. City of Hope’s affiliated group of organizations includes Translational Genomics Research Institute and AccessHopeTM.