A team of Italian scientists studied nearly 19,000 people, all of whom were eating a traditional Mediterranean diet. They were monitored for cardiovascular disease, including heart attacks and strokes.
In 2013, a study in the New England Journal of Medicine said the traditional Mediterranean diet reduced the risk of heart attack or stroke by up to 30 percent.
But this latest study, published in the International Journal of Epidemiology, goes further and suggests those who went to university and earned more than 40,000 euros (US$47,000) got considerably more benefit than those with lower income and education.
"The cardiovascular benefits associated with the Mediterranean diet in a general population are well known. Yet for the first time our study has revealed that the socioeconomic position is able to modulate the health advantages linked to Mediterranean diet," said the report's author, Dr. Marialaura Bonaccio from the University of Insubria.
"In other words, a person from low socioeconomic status who struggles to follow a Mediterranean model, is unlikely to get the same advantages of a person with higher income, despite the fact that they both similarly adhere to the same healthy diet," she added.
The reason for the difference is not clear although it may be because the wealthier and more educated tend to buy organic foods — which are usually more expensive — and cook them in a healthier way.
"These substantial differences in consuming products belonging to Mediterranean diet lead us to think that quality of foods may be as important for health as quantity and frequency of intake," said the report's co-author Dr. Licia Iacoviello.
"During recent years, we have documented a rapid shift from the Mediterranean diet in the whole population, but it might also be that the weakest citizens tend to buy Mediterranean food with lower nutritional value," said Dr Giovanni de Gaetano, director of the University's Department of Epidemiology and Prevention.
"We cannot be keeping on saying that the Mediterranean diet is good for health if we are not able to guarantee an equal access to it."