It has long been known that air pollution affects the risk ̵
A new study finds that higher consumption of omega-3 fatty acids found in oily fish such as salmon, sardines and sea trout and in some plant sources such as walnuts and flaxseed, is associated with reduced asthma symptoms in urban children exposed to relatively high level of indoor air pollution.
"We know that asthma is a disease driven by inflammation," Dr. 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 produce by-product molecules known as "pro-resolving mediators" that make their way into our lungs. "They help solve inflammation," Brigham says.
Due to this anti-inflammatory effect, Brigham and her colleagues had a clue that dietary habits with omega-3 fatty acids can help to mitigate the effects of air pollution on children's symptoms. To study this, they followed diet and indoor air pollution levels (from sources, including smoke, dust and allergens) at home to 135 children, mostly African American and all with asthma, in Baltimore, Md.
They measure two types of indoor air pollution consisting of different sizes of particles: PM2.5 (fine inhalable particles that are 2.5 microns or less) and the somewhat larger PM10. These particles are too small for us to see, but they can enter our airways, and the smaller size – PM2.5 – can infuse deep into our lungs.
"What we found was that higher reporting intake of omega-3 was associated with reduced effects of indoor particles on symptoms," Bright says. "Children who ate more omega-3 seemed to be more resistant to PM's effects."
Brigham and her team also assessed the intake of omega-6 fatty acids found in vegetable oils and are abundant in many processed foods containing oil. Normally, Americans eat far more omega-6 acids compared to omega-3s, and that was the same for all children in the Baltimore study. And the study found that children who consumed the most omega 6 fatty acids had more severe asthma symptoms.
Brigham says omega 6 fatty acids in inflammation are complicated. Some of the by-products of omega-6 acids, such as leukotrienes, have been shown to be pro-inflammatory. "Leukotrienes are one of the molecules known to be responsible for the inflammation of asthma," she says.
Now, because this was an observation study, scientists cannot prove that omega-3 acids caused a decrease in symptoms or that the high intake of omega-6 acids caused more serious symptoms. But the results fit with a large number of evidence documenting the anti-inflammatory effects of omega 3's.
And when it comes to dampening the effects of air pollution, there are other studies that support the idea that dietary intervention can help provide protection.
"This study adds to a growing body of evidence that diet – Western, Mediterranean coast, etc. – can affect the health effects of exposure to air pollution," says Kym Gowdy, assistant professor of pharmacology and toxicology at East Carolina University.
She points to a recent study published in the journal Circulation which found a Mediterranean style, reduced the risk of death from cardiovascular disease related to prolonged exposure to air pollutants.
"The study by Dr. Brigham supports [new] the overall perception that nutritional status is an important factor that should be considered to improve protection against air pollution n," said Neil Alexis, professor at the UNC School of Medicine in Chapel Hill, NC
And although Brigham's study focused on the useful fatty acids in foods, Alexis notes that another study has found that antioxidant supplements can also help to mitigate the effect of ozone exposure on small airways. in children who have moderate to severe asthma. Meanwhile, a separate 2018 study in adults found that vitamin E helped reduce inflammatory features of asthma.
Generally, a diet rich in fruits, vegetables, nuts and seeds and healthy fats – including omega 3's – are many proven health benefits, including a reduced risk of cardiovascular disease. The new study points to a further potential benefit, especially for people exposed to air pollution. And when it comes to getting enough omega-3 fatty acids: US dietary guidance recommends that adults eat 8 ounces of shellfish per week and young children a little less.