Healthy adults who eat a diverse diet, with at least 8-10 grams of soluble fibre such as grains, beans, lentils, nuts and some fruits and vegetables daily, have fewer antibiotic-resistant microbes in their guts, according to a study.

Microbes that have resistance to various commonly-used antibiotics such as tetracycline and aminoglycoside are a significant source of risk for people worldwide, with the widely held expectation that the problem of antimicrobial resistance (AMR) - the term that refers to bacteria, viruses, and fungi that are resistant to antibiotics - is likely to worsen throughout the coming decades.

Antimicrobial resistance in people is largely based on their gut microbiome, where the microbes are known to carry genetically encoded strategies to survive contact with antibiotics.

"The results lead directly to the idea that modifying the diet has the potential to be a new weapon in the fight against antimicrobial resistance. And we're not talking about eating some exotic diet either, but a diverse diet, adequate in fibre," said research molecular biologist Danielle Lemay at the US Department of Agriculture's Agricultural Research Service.

In the study, published in the journal mBio, the researchers found that regularly eating a diet with higher levels of fibre and lower levels of protein, especially from beef and pork, was significantly correlated with lower levels of antimicrobial resistance genes (ARG) among their gut microbes.

Those with the lowest levels of ARG in their gut microbiomes also had a greater abundance of strict anaerobic microbes, which are bacteria that do not thrive when oxygen is present and are a hallmark of a healthy gut with low inflammation. Bacterial species in the family Clostridiaceae were the most numerous anaerobes found.

But the amount of protein in the diet was not a top predictor of high levels of ARG. The strongest evidence was for the association of higher amounts of soluble fibre in the diet with lower levels of ARGs.

"Surprisingly, the most important predictor of low levels of ARG, even more than fibre, was the diversity of the diet. This suggests that we may want to eat from diverse sources of foods that tend to be higher in soluble fibre for maximum benefit," Lemay added.

On the other hand, those people who had the highest levels of ARG in their gut microbiomes were found to have significantly less diverse gut microbiomes compared to groups with low and medium levels of ARG.

"Our diets provide food for gut microbes. This all suggests that what we eat might be a solution to reduce antimicrobial resistance by modifying the gut microbiome," Lemay said.