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A study published in Nature found that among 173 hospitalized cancer patients, higher sugar intake in the 48 hours before antibiotic treatment was associated with a greater decline in gut bacterial diversity. Mouse experiments also linked dietary sucrose during antibiotic exposure to a sharp rise in Enterococcus, but researchers say clinical trials are needed to learn whether reducing sugar improves patient outcomes.
A study of 173 hospitalized cancer patients found that higher sugar intake in the 48 hours before antibiotic treatment was associated with a greater drop in gut bacterial diversity, raising the possibility that diet can compound antibiotics’ effects on beneficial microbes. The research, published online Sept. 30 in Nature, also found increases in Enterococcus faecium among patients with sugary diets and antibiotic exposure; it does not establish that sugar caused the changes or that cutting sugar improves health outcomes.
Researchers from NYU Langone Health, City of Hope and Memorial Sloan Kettering analyzed records of 9,419 meals and tracked changes in participants’ gut microbiomes. For every additional 100 grams of sugar consumed during the 48 hours before treatment, they observed an additional 21% decline in alpha diversity, a measure of the variety of bacterial species in the gut. This is a study-specific association, not evidence that an individual serving of sugar will produce a predictable change.
The researchers also reported that sugary diets combined with antibiotic treatment were associated with increases in Enterococcus faecium, a bacterial species linked to infections that can be difficult to treat. In mouse experiments, animals given the antibiotic biapenem while eating sucrose had gut Enterococcus populations 16.3 times higher by day three and 33.4 times higher by day six. Those animal results support further investigation but do not show what dietary changes would do for people.
The team says one possible explanation is that bacteria able to survive antibiotics use dietary sugars to expand. The study did not establish whether sugar directly fuels Enterococcus in patients, weakens competing bacteria, or affects the microbiome by another route. Researchers say clinical trials are needed before they can determine whether changing sugar intake during or after antibiotics improves patient outcomes.
Diet May Compound Antibiotic Effects
Antibiotics can disrupt the gut microbiome by killing beneficial bacteria as well as the microbes causing an infection. A loss of bacterial diversity may leave the gut ecosystem less able to resist the growth of potentially harmful species. The study suggests diet could be one factor associated with that disruption, though its findings do not establish cause and effect.
The question may carry particular weight for people receiving intensive cancer care. Patients with blood cancers may receive prolonged antibiotics and other treatments that affect the microbiome; the study’s authors note that microbiome injury in this group has been associated with infections and worse outcomes. But this research measured diet and microbiome changes, not whether eating less sugar reduced infections, complications or mortality. No clinical benefit from a low-sugar diet was tested.
For readers taking antibiotics, the findings are a research signal, not a reason to change treatment or follow a restrictive diet without professional guidance. Antibiotics should be taken as prescribed. Anyone considering a dietary change while being treated, particularly a hospitalized patient or someone undergoing cancer treatment, can discuss it with their care team.
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Why Researchers Tracked Cancer Patients
The investigators studied people with blood cancers because they frequently receive antibiotics and, while hospitalized, their meals and microbiome samples can be monitored closely. The team recorded food intake at each meal and collected microbiome samples daily, producing detailed observations across 9,419 meals and 173 patients.
Some patients with blood cancers undergo stem cell transplants and remain in hospital for weeks while receiving chemotherapy and antibiotics. During that time, both diet and gut bacteria can change. Researchers said this setting offered a way to examine how everyday factors may relate to the microbiome during intensive treatment; it also means the results may not apply in the same way to people taking a short course of antibiotics outside hospital.
The study builds on concern that antibiotics can reduce microbial diversity and allow some surviving organisms to expand. Its contribution is the reported link between recorded sugar intake and microbiome changes in this patient group, combined with mouse experiments showing a similar pattern under controlled conditions.
“The microbiome is emerging as an important factor in cancer care.”
— Marcel van den Brink, study co-senior author and chief physician executive at City of Hope
Cause and Patient Benefits Unproven
The patient findings are observational: they show an association between sugar intake and microbiome changes, not that sugar caused those changes. The report does not establish whether the association applies to people outside the hospitalized blood-cancer population, or whether different types of sugar, specific foods or different antibiotic regimens produce the same pattern.
It also remains unknown whether reducing sugar during or after antibiotic treatment would preserve bacterial diversity, prevent Enterococcus growth or improve outcomes such as infection rates. The mouse findings cannot answer those questions for people. The researchers say the mechanism is unresolved and that clinical trials are needed to test dietary changes and patient outcomes.
Clinical Trials Are the Next Test
The researchers identified clinical trials as the next step: studies would need to test whether a short-term dietary change during or after antibiotic treatment affects microbiome measures and meaningful health outcomes. Until such evidence is available, the findings do not support a specific sugar limit or a general recommendation to alter diet during antibiotics.
Further work may also examine how sugar relates to Enterococcus and other gut bacteria, and whether the results hold in patient groups beyond those studied. For now, people should follow their prescribed antibiotic regimen and consult a qualified clinician or dietitian before making dietary changes during treatment, especially in the setting of cancer care or hospitalization.
Key Questions
Does this study prove sugar makes antibiotics more damaging?
No. In patients, researchers found an association between higher sugar intake before treatment and a greater decline in gut bacterial diversity. The observational data do not prove that sugar caused the change.
How many people were studied?
The patient analysis included 173 hospitalized cancer patients and records of 9,419 meals. The researchers also conducted separate experiments in mice.
Should I stop eating sugar while taking antibiotics?
The study did not test whether reducing sugar improves health outcomes, and it does not set a recommended sugar limit. Keep taking antibiotics as prescribed and ask a qualified health professional before making dietary changes during treatment.
What is Enterococcus faecium?
It is a bacterial species found in the study’s microbiome analysis and linked to infections that can be difficult to treat. The researchers observed increases associated with sugary diets and antibiotic treatment; the finding does not mean every person taking antibiotics will develop an infection.
What research is needed next?
The study authors say clinical trials should test whether short-term dietary changes during or after antibiotic treatment affect microbiome measures and patient outcomes, including whether they change infection risk.
Source: rss
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