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It has long been known that air pollution influences the risk – and severity – of asthma. More and more evidence shows that food can also play a role.
A new study reveals that an increased consumption of omega-3 fatty acids, found in oily fish such as salmon, sardines and lake trout and in some plant sources such as nuts and flax seeds, is related to a reduction in asthma symptoms in children in cities exposed to fairly high levels of indoor air pollution.
"We know that asthma is a disease caused by inflammation," says Dr. Emily Brigham, a pulmonologist at Johns Hopkins University and co-author of the study. As our body digests fish, omega-3 fatty acids generate byproduct molecules called "pro-resolving mediators" that enter our lungs. "They help to solve the inflammation," says Brigham.
Given this anti-inflammatory effect, Brigham and his colleagues felt that diets rich in omega-3 fatty acids may help mitigate the effects of air pollution on children's symptoms. To study this, they followed dietary patterns and indoor air pollution levels (from sources such as smoke, dust, and allergens) in 135 children, mostly African-Americans and suffering from high blood pressure. Asthma in Baltimore, Maryland.
They measured two types of indoor air pollution, consisting of different particle sizes: PM2.5 (fine respirable particles 2.5 microns or less) and slightly larger PM10s. These particles are too small for us to see, but they can enter our airways and the smaller size – PM2.5 – can lodge deep in our lungs.
"What we found was that higher omega-3 consumption would have been badociated with reduced effects of suspended particles on symptoms inside buildings. "said Brigham. "Children who ate more omega-3s seemed to better withstand the effects of particles."
Brigham and his team also evaluated the intake of omega-6 fatty acids found in vegetable oils and in abundance in many processed foods containing oil. In general, Americans consume far more omega-6 than omega-3s, which was also the case for all children in the Baltimore study. The study also found that children who consumed the most omega-6 fatty acids had more serious asthma symptoms.
Brigham says that the role of omega 6 fatty acids in inflammation is 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 inflammation related to asthma," she said.
As this was an observational study, researchers can not prove that omega-3 acids caused a decrease in symptoms nor that the high consumption of omega-6 acids caused more serious symptoms. But the results are consistent with the many evidence documenting the anti-inflammatory effects of omega-3s.
And, in terms of mitigating the effects of air pollution, other studies support the idea that dietary interventions can help to provide protection.
"This study adds to an increasing number of publications suggesting that food, western, Mediterranean, etc. – can influence the health effects of air pollution exposure," he said. said Kym Gowdy, badistant professor of pharmacology and toxicology at East Carolina University.
She cites a recent study published in the journal circulation a Mediterranean diet has reduced the risk of death from cardiovascular disease due to prolonged exposure to air pollutants.
"The [new] Dr. Brigham's study confirms the general idea that nutritional status is an important factor to consider in enhancing protection against air pollution, "says Neil Alexis, a professor at Chapel's UNC School of Medicine. Hill, NC
And although Brigham's study focuses on fatty acids useful in foods, Alexis notes that another study found that antioxidant supplements can help mitigate the impact of exposure to ozone on the small airways of children with moderate to severe asthma. At the same time, a separate study conducted in 2018 in adults revealed that vitamin E helped to reduce the inflammatory characteristics of asthma.
In general, a diet rich in fruits, vegetables, nuts and seeds and healthy fats – including omega-3 – has many health benefits, including a reduced risk of cardiovascular disease. The new study highlights another potential benefit, especially for people exposed to air pollution. And when it comes to getting enough omega-3 fatty acids: The American diet recommendations recommend that adults consume 8 ounces of seafood a week and younger children a little less.
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SCOTT SIMON, HOST:
There is a trade group that has existed for over 100 years, almost as long as B. J. Leiderman made our musical theme. The Salt Institute has represented the salt industry of the United States, which sells everything from salt-laden salts to salt-glazed roads on your food. The Salt Institute closed on March 31st. Nell Greenfieldboyce, of NPR, wanted to know why.
NELL GREENFIELDBOYCE, BYLINE: Earlier this month, Michael Jacobson visited the Salt Institute's website. And he saw a surprising announcement.
MICHAEL JACOBSON: I was surprised, like everyone else, to see that this centennial professional badociation was closing down.
GREENFIELDBOYCE: And how did you feel about it?
JACOBSON: I felt good.
GREENFIELDBOYCE: Jacobson is the co-founder of the Center for Science in the Public Interest, who calls himself the food watchdog in America. He says Americans eat too much salt, which can lead to high blood pressure and heart disease. And he says that for years the Salt Institute has been attacking studies that support salt reduction while promoting studies suggesting that less salt could be dangerous.
JACOBSON: The Salt Institute, for 30 years that I am, has only blurred the tracks in terms of salt and health.
GREENFIELDBOYCE: He has already been invited to compete at the Salt Institute as part of the "Colbert Report". Colbert asked Lori Roman, president of the Salt Institute, about the idea that salt can be bad for you.
(SOUNDBITE OF TV SHOW, "THE COLBERT REPORT")
STEPHEN COLBERT: All high falutin medical organizations say salt is like – just fill a gun with salt and ignite it in your brain.
(TO LAUGH)
LORI ROMAN: Well, I think the diet police practice maybe a bit of police brutality because, unlike some of the products she has targeted in the past, you need salt to live on. You can not survive without it. That's the reason why …
COLBERT: More than that, if you eat enough salt, you'll curse yourself like an ox, and you'll live forever, right?
(TO LAUGH)
GREENFIELDBOYCE: I asked Lori Roman about the closure of the institute. She would only send me a statement from her board of directors. He added that the Salt Institute had helped the public understand the essential nature of the product, without giving any explanation. Board members work for large salt companies like Morton Salt, Cargill, Compbad Minerals. I reached out their hand. They've basically given me zero information. So I called Dick Hanneman. He has been president of the Salt Institute for about a quarter of a century.
DICK HANNEMAN: I am saddened to learn that this is going away because I thought it was useful.
GREENFIELDBOYCE: He says it has worked on important issues, such as the best use of salt on the roads of the country. And as for nutrition, he says they've pushed back the government's anti-salt campaigns, even sued the Department of Health and Human Services.
HANNEMAN: So we approached the issue not politically, but by science trying to point out the first point, the weakness of the argument of the '60s and' 70s on which politics had been adopted, and then the need to develop more science.
GREENFIELDBOYCE: He says that when the group was created as an badociation of salt producers in 1914, there were hundreds of salt producers. Later, the name changed, as did the industry. Finally, the group had fewer than a dozen member companies.
HANNEMAN: So if some big companies lose interest, the funding disappears.
GREENFIELDBOYCE: He does not know what machinations led to his closure. But he says that salt itself is here to stay.
HANNEMAN: Humans continue to eat between 2,400 and 5,500 milligrams of sodium a day.
GREENFIELDBOYCE: And that's way too much, according to independent national academies of science, engineering and medicine. This month alone, adults should consume less than 2,300 milligrams of sodium daily. That's about a total of one teaspoon. But remember, most salt comes from prepared foods rather than your salt cellar. Nell Greenfieldboyce, NPR News.
(SOUND MUSIC) Transcription provided by NPR, Copyright NPR.
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