Sugar May Worsen Antibiotic Damage to the Gut, Study Finds

Antibiotics can wipe out helpful gut bacteria along with harmful ones. New research suggests that what people eat while taking them, particularly sugar, may make that damage worse.

The study, published in Nature, was led by senior investigator Jonathan Peled, M.D., Ph.D., a medical oncologist at Memorial Sloan Kettering Cancer Center who specializes in bone marrow transplantation and cellular therapies for blood cancers. Peled spoke with The Educated Patient about the findings.

Tracking every bite in the hospital

The researchers followed 173 adults undergoing bone marrow transplants at Memorial Sloan Kettering. They tracked more than 9,400 meals and analyzed about 1,000 stool samples. Because patients ordered nearly all their food from the hospital kitchen, the team could record exactly what and how much each person ate, down to the ingredients in each recipe.

That level of detail is rare, Peled said. Most diet studies rely on people remembering what they ate over weeks or months, which is difficult to report accurately.

Patients who ate more sweets and sugars while on antibiotics had less diverse gut bacteria and greater growth of Enterococcus, a bacterium that can cause bloodstream infections in people with weakened immune systems. Among patients with higher sugar intake, longer courses of broad-spectrum antibiotics were also linked to higher mortality.

In follow-up experiments in healthy mice, adding table sugar to an antibiotic greatly increased the growth of Enterococcus. Sugar alone, without antibiotics, had no effect.

“We think that antibiotics do an initial round of damage, and then the sugar somehow makes that worse,” Peled said.

Exactly why remains unclear. Harmful bacteria may use sugar as fuel, sugar may change how the remaining bacteria compete, or it may affect the body in ways that favor harmful growth.

A low-cost idea that still needs testing

Many people try probiotics or other remedies to protect their gut during antibiotics, but Peled said the evidence behind them isn’t strong. Cutting back on sugar for the length of an antibiotic course could be a simple alternative.

“Unlike new drugs that are very expensive and have side effects, avoiding sugar for a week is something that anybody ought to be able to do at low or no cost,” he said.

Still, Peled stressed that the findings come mostly from a very ill, heavily treated patient group and from mice. Clinical trials are needed to know whether limiting sugar truly helps, including for healthier people taking a short course of antibiotics.

“We need funding for clinical trials to guide dietary recommendations,” he said.

Until then, he leaves decisions about diet during antibiotic treatment to patients and their doctors.