Researchers have shown that eating the equivalent of two thirds of a teaspoon of olive oil every day can reduce the effect of air pollution on the heart.
A separate study has also shown that olive oil can lower blood pressure when eaten with certain vegetables.
Professor Philip Eaton, Professor of Cardiovascular Biochemistry at King's College London, said: "The findings of our study help to explain why previous research has shown that a Mediterranean diet supplemented with extra-virgin olive oil or nuts can reduce the incidence of cardiovascular problems like stroke, heart failure and heart attacks."
Exposure to high levels of air pollution is linked to an increased risk of heart disease, stroke and asthma.
Microscopic particles from diesel engines, for example, increase inflammation and cause blood vessels to harden, increasing blood pressure and the risk of clots.
The findings, based on 42 healthy adults who were exposed to controlled levels of air pollution, were presented at the American Thoracic Society International Conference.
Dr Haiyan Tong, a research biologist with the United States Environmental Protection Agency, said: "Our study suggests that use of olive oil supplements may protect against the adverse vascular effects of exposure to air pollution particles.
"If these results are replicated in further studies, use of these supplements might offer a safe, low cost, and effective means of counteracting some of the health consequences of exposure to air pollution."
A third study has found that pregnant women exposed to air pollution during their second trimester are at greater risk of having children with asthma.
It was known that air pollution damages the lungs of the developing baby but it has now been found that weeks 12 to 24 are the peak period.
The findings, from Icahn School of Medicine and Mount Sinai in New York, were also presented at the American Thoracic Society International Conference.
The study included 430 children followed from birth to age seven.
