China, India, and many other countries are smothering in toxic smog.

Many Americans breathe much cleaner air, but that’s not so true of people who live in U.S. cities with heavy traffic.

All vehicle fumes harm health, but the worst pollutants come from diesel-powered vehicles, factories, and power plants.

The most harmful offenders are fine “PM2.5” particles, so called because they're smaller than 2.5 millimeters.

Years of breathing high levels of PM2.5 can cause respiratory and cardiovascular diseases, diabetes, brain degeneration, and cancer.

The reasons why PM2.5 particles are so damaging throughout the body aren't fully understood, but appear linked to oxidative (free radical) stress, DNA damage, and the immune system's responses to pollutants, especially inflammation.

Now, the results of a lab study in mice suggest that omega-3 fatty acids — especially the kinds found in seafood (DHA and EPA) — provide some protection from damaging PM2.5 particles.

Study finds that omega-3s protect mice against pollutants
The new findings come from scientists at Massachusetts General Hospital, Harvard Medical School, and China’s Guangdong (Canton) Medical College.

For the first part of their study, they exposed mice to fluorescent PM2.5 particles and tracked their distribution in the animals’ bodies (Li XY et al. 2017).

That experiment showed, for the first time, that PM2.5 particles penetrate the “pulmonary barrier” protecting the lungs, and travel to the brain, liver, spleen, kidneys, and testes.

Mice exposed to airborne PM2.5 also showed a sharp rise in inflammation and oxidative (free radical) stress, compared to mice that breathed clean air.

Next, they tested the effects of dietary omega-3 fatty acids on the inflammation and oxidative stress triggered by air polluted with PM2.5.

The American-Chinese team used two different groups of mice to test the effects of omega-3s:

  • Mice given omega-3 supplements following exposure to PM2.5-polluted air.
  • Mice genetically modified to possess high levels of omega-3s in their tissues.

For comparison, they also exposed a control group of mice — which had no omega-3 advantage — to PM2.5-polluted air.

Encouragingly, both groups of omega-3 test mice suffered much less inflammation and oxidative stress.

As the researchers wrote, "[Omega-3 fatty acids] present an immediate and practical solution for reducing the disease burden of air pollution." (Li XY et al. 2017)

Would people benefit, and at what dose?
The study’s lead author — Dr. Jing Kang of Massachusetts General Hospital — believes their results should translate to humans.

As he said, “I can anticipate the same things [that happen in mice] would happen in humans, because many other inflammatory diseases in humans can be treated with OFAs [omega-3 fatty acids]. We feel very confident OFAs can do something very good.”

His confidence seems well-placed, given the positive findings of two small human trials that tested the effects of omega-3s against air pollution. For more about those studies, see Does Fish Fight the Dangers of Dirty Air? and Omega-3s Help Protect against Pollution Harm.

And seven years ago, a study found that higher fish consumption during pregnancy may help protect a woman’s fetus against the harmful effect of her own exposure to airborne pollutants (Jedrychowski W et al. 2010).

Dr. Kang recommended the people act on their findings: “I would definitely recommend taking OFAs to counter air pollution problems,” he said. “[Omega-3 fatty acids] are well known to have many other health benefits and the key thing is they are not like a drug, but a nutrient with so many benefits.”

He also said that doses given to the mice would translate to a human dose of about three grams of omega-3s per day.

That’s the amount of omega-3s in about two three-ounce (85g) portions of fatty fish — such as salmon, tuna, or mackerel — or several fish oil capsules, depending on the dose of omega-3 EPA + DHA in each capsule.

That’s much more than most Americans get, according to the Mayo Clinic: “The average American consumes about 1.6 grams of omega-3 fatty acids daily. About 1.4 grams of this comes from [plant-source] ALA, while [only] 0.1 to 0.2 grams [come] from [seafood-source] EPA and DHA.”

Compared with seafood source omega-3 DHA and EPA, the omega-3 ALA found in certain plant foods is not nearly as effective at fighting inflammation.

And the human body can only convert small amounts of plant-source ALA into the seafood-source omega-3 DHA and EPA used in the mouse study and prior human studies.

So, the average American would need to raise their DHA + EPA intake sharply if they want to ensure maximum protection against air pollution.

People living in areas with relatively clean air wouldn’t need such high doses, while people living in air-polluted cities should probably try to get three grams of omega-3 DHA + EPA per day.

Since some of the damage caused by air pollutants comes from inflammation and oxidative stress, people could probably take lower doses of omega-3s if they radically reduce their intake of omega-6 fatty acids from vegetable oils.

The Mayo Clinic stressed that point in their guidance about omega-3s:
“In Western diets, people eat about 10 times more omega-6 fatty acids than omega-3 fatty acids. These large amounts of omega-6 fatty acids come from vegetable oils such as corn oil, sunflower oil, and soy oil. Because omega-6 and omega-3 fatty acids compete in the body, benefits may be reached either by decreasing omega-6 intake or increasing omega-3 intake.”

The extremely high omega-6 intake in the standard American diet produces a pro-inflammatory environment in the body, which would make the effects of air pollutants worse.

And as Dr. Kang said, increased omega-3 intake would bring side benefits to heart, brain, and metabolic health.

B vitamins may help, too
A small clinical study published last April found that supplemental B vitamins also afford strong protection against air pollution.

Researchers from Columbia University recruited 10 non-smoking men aged 18 to 60, and exposed them to polluted air after giving them this daily regimen of B vitamins:

  • 2.5 mg of folic acid
  • 50 mg of vitamin B6
  • 1 mg of vitamin B12

The results showed that the B vitamin supplements nearly reversed any negative effects on the volunteers’ cardiovascular and immune systems and weakened the adverse effects of air pollution on heart rate by 150 percent.

So if you live in a city with air polluted by factories and vehicles, you should consider taking those B vitamins, in addition to eating fatty fish and/or taking omega-3 supplements.



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