These nitro fatty acids are formed when consuming spinach, celery and carrots that are filled with nitrates and nitrites, along with avocado, nuts and olive oils that contain healthy fats.
Nitro fatty acids appear to inhibit an enzyme known as soluble epoxide hydrolase, which regulates blood pressure, said the research in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal.
The study was based on experiments in lab mice, and was funded by the British Heart Foundation.
"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," said Philip Eaton, professor of cardiovascular biochemistry at King's College London.
While most experts agree that the Mediterranean diet -- which consists of lots of vegetables, fish, grains, red wine and fatty nuts and oils -- brings health benefits, there has been little scientific consensus about how or why.
Some have touted red wine as a driving force behind the ability of Europeans to eat high fat cheeses and meats while maintaining better overall health than Americans.
But research published last week found that a key antioxidant in red wine, resveratrol, did not help people in Italy live longer or avoid cancer or heart disease.