Researchers from Texas Tech University find that the heart-healthy benefits of walnuts might just come from how they impact the gut. Specifically, scientists found that the tasty snack improves heart function by first creating a healthier balance of beneficial bacteria.

“Research has shown that walnuts may have heart-healthy benefits like lowering cholesterol levels and blood pressure,” says Mansi Chandra, an undergraduate researcher at Juniata College in Pennsylvania, in a media release. “This motivated us to look at how walnuts benefited the gut microbiome and whether those effects led to the potential beneficial effects. Our findings represent a new mechanism through which walnuts may lower cardiovascular disease risk.”

The research team used a set of techniques called metatranscriptomics to study gene expression and the bacteria in the gastrointestinal tract from fecal samples. The technology can quantify and monitor gene expression levels over time in response to environmental changes, like ones prompted by a person’s diet. The analysis used 35 samples from a previous study in which people at high cardiovascular risk were put on a two-week standard Western diet and then randomly assigned to one of three study diets.