Researchers published their results in JAMA Network Open. They study consisted of nearly 26,000 subjects who consumed a diet heavy in plants and olive oil and low in meats and sugar.

“Our study has a strong public health message that modest changes in known cardiovascular disease risk factors, particularly those relating to inflammation, glucose metabolism and insulin resistance, contribute to the long-term benefit of a Mediterranean diet on cardiovascular disease risk,” said Shafqat Ahmad, a research fellow at the Brigham and Women’s Hospital and at the Harvard Chan School and study lead author.

“This understanding may have important downstream consequences for the primary prevention of cardiovascular disease.”

For up to 12 years, a team of investigators from Brigham and Women’s Hospital, Harvard Medical School and the Harvard T.H. Chan School of Public Health looked at the participants’ food intake questionnaires and measured blood samples biomarkers. They kept an eye out for events of heart attack, stroke, coronary arterial revascularisation and cardiovascular death.

Overall, the team reported a 29% decrease in inflammation, which indicates a reduction in cardiovascular disease risk, a nearly 30 % change in glucose metabolism and insulin resistance and a more than 27% change in body mass index.

“While prior studies have shown benefit for the Mediterranean diet on reducing cardiovascular events and improving cardiovascular risk factors, it has been a black box regarding the extent to which improvements in known and novel risk factors contribute to these effects,” said Samia Mora, a cardiovascular medicine specialist at the Brigham and Harvard Medical School and study corresponding author.

“In this large study, we found that modest differences in biomarkers contributed in a multi-factorial way to this cardiovascular benefit that was seen over the long term.”