The research suggested people who eat a Mediterranean-like diet have healthier hearts, but those studies couldn´t rule out that other health or lifestyle differences had made the difference.
For the new trial, researchers randomly assigned study volunteers at risk of heart disease to a Mediterranean or standard low-fat diet for five years, allowing the team to single out the effect of diet, in particular.
The study developed in Spain assigned almost 7,500 older adults with diabetes or other heart risks to one of three groups.
Two groups were instructed to eat a Mediterranean diet – one supplemented with extra-virgin olive oil and the other with nuts, both donated for the study – with help from personalized advice and group meetings. The third study group ate a "control" diet, which emphasized low-fat dairy products, grains and fruits and vegetables.
Over the next five years, 288 study participants had a heart attack or stroke or died of any type of cardiovascular disease.
People on both Mediterranean diets were 28 to 30 percent less likely to develop cardiovascular disease than those on the general low-fat diet, the researchers reported Monday in the New England Journal of Medicine.
It´s the blend of Mediterranean diet components – not one particular ingredient – that promotes heart health, according to Martinez-Gonzalez.
Martinez-Gonzalez suggested people seeking to improve their diet start with small changes, such as forgoing meat one or two days per week, cooking with olive oil and drinking red wine with meals rather than hard alcohol.
Replacing a high-carbohydrate or high-saturated fat snack with a handful of nuts is also a helpful change, said Teresa Fung, a nutrition researcher at Simmons College in Boston who also wasn´t on the study team.