It’s long been known that air pollution influences the risk — and severity — of asthma. Now, there’s emerging evidence that diet can play a role, too.

A new study finds that higher consumption of omega-3 fatty acids, found in oily fish such as salmon, sardines and lake trout, and in some plant sources such as walnuts and flaxseed, is linked to reduced asthma symptoms in city kids who are exposed to fairly high levels of indoor air pollution.

“We know that asthma is a disease that’s driven by inflammation,” explains Dr. Emily Brigham, a pulmonologist at Johns Hopkins University and co-author of the study. As our bodies digest fish, the omega-3 fatty acids generate byproduct molecules known as “pro-resolving mediators” that make their way into our lungs. “They help to resolve inflammation,” Brigham says.

Given this anti-inflammatory effect, Brigham and her colleagues had a hunch that diets rich in omega-3 fatty acids may help attenuate the effects of air pollution on kids’ symptoms. To study this, they tracked the diets and indoor air pollution levels (from sources including smoke, dust and allergens) in the homes of 135 children, mostly African-American and all with asthma, in Baltimore, Md.