Researchers found that among the study's participants, adherence to the Mediterranean diet was more protective than physical activity.
The study, conducted in Greece, bolsters evidence from earlier studies pointing to the diet's health benefits and is the first to track 10-year heart disease risk in a general population. Most previous studies have focused on middle-aged people.
"Our study shows that the Mediterranean diet is a beneficial intervention for all types of people - in both genders, in all age groups, and in both healthy people and those with health conditions," said Ekavi Georgousopoulou, a PhD candidate at Harokopio University in Athens, Greece, who conducted the study along with Demosthenes B Panagiotakos, professor at Harokopio University.
The study is based on data from a representative sample of more than 2,500 Greek adults, ages 18 to 89, who provided researchers with their health information each year from 2001 to 2012.
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Participants also completed in-depth surveys about their medical records, lifestyle and dietary habits at the start of the study, after five years and after 10 years.
Overall, nearly 20 per cent of the men and 12 per cent of the women who participated in the study developed or died from heart disease, a suite of conditions that includes stroke, coronary heart disease caused by the buildup of plaque in the heart's arteries, acute coronary syndromes such as heart attack, and other diseases.
Those who scored in the top-third in terms of adherence to the Mediterranean diet, indicating they closely followed the diet, were 47 per cent less likely to develop heart disease over the 10-year follow-up period as compared to participants who scored in the bottom-third, indicating they did not closely follow the diet.
Each one-point increase in the dietary score was associated with a 3 per cent drop in heart disease risk, researchers said.
The study will be presented at the American College of Cardiology's 64th Annual Scientific Session in San Diego, March 14 to March 16.