Daily supplements of fatty acid-rich fish oil may counteract the effects of air pollution on the heart, researchers report.

"The cardiac responses to air pollutants were dramatically reduced in those on fatty acids," said Dr. Fernando Holguin, an assistant professor of medicine at Emory University School of Medicine. He presented the research this week at the American Thoracic Society's annual meeting in San Diego.

Holguin's team tracked the cardiac health of 50 elderly people, all nursing home residents averaging 70 years of age and living in smog-plagued Mexico City.

Each resident received a one-gram oil capsule twice a day (once in the morning and again in the evening) containing omega-3 fatty acids. Half of the group received fish oil capsules and the other half soy oil capsules.

The researchers took ongoing measurements of each participant's cardiac function, focusing specifically on their heart rate variability. Heart-rate variability refers to the heart rate alterations from beat to beat.

"Exposure to the particles of air pollution reduces heart rate variability, and taking the omega-3 fatty acids increased it," Holguin explained. "Increased heart rate variability reduces heart disease risk."

The fish oil was much better at keeping heart rate healthy than was the soy oil, the Emory team found. "Those on soy oil had just marginal protection," Holguin said, while "those on fish oil had a complete abolishment of the effect of the [smog] particles on the heart."

Another expert, Dr. Zi-Jian Xu, a staff cardiologist at Santa Monica-UCLA Medical Center and an assistant clinical professor of medicine at the David Geffen School of Medicine, UCLA, said he is not surprised by the results. "Fish oil has been found to reduce cardiovascular events, mainly heart attack and stroke," he said. "It has also been shown to modestly reduce the risk of another heart attack. The theory is that omega-3 fatty acids can improve cardiovascular health."

The new finding is also consistent with previous research, Xu added.

Holguin advises that people follow the advice of the American Heart Association (AHA) with regards to their daily intake of omega-3 fatty acids. The AHA currently recommends that individuals with documented heart disease eat about one gram of omega-3 fatty acids a day, preferably from fatty fish. Beyond that, supplements could be considered "in consultation with the physician," the AHA recommends.

Those without documented heart disease are advised by the AHA to eat a variety of fish, preferably fatty species such as salmon, mackerel and sardines, at least twice a week and to include oils and foods rich in alpha-linolenic acid (flaxseed, canola and soybean oils, flaxseed and walnuts) in the diet.