WASHINGTON, August 2, 2014 –A 2013 study in the New England Journal of Medicine concluded that a Mediterranean diet supplemented with olive oil and nuts beat out a conventional low fat diet in reducing cardiovascular risk. The health benefits of a Mediterranean diet have been discussed and lauded for decades, but this is the first major study that specifically links diet with reduction in heart disease.
With the participation of over 7,400 people randomly assigned to either a Mediterranean diet supplemented with olive oil, a Mediterranean diet supplemented with nuts, or a low-fat control diet, the study found that both Mediterranean diet groups saw close to a 30% reduction in cardiovascular events like strokes and heart attacks in comparison to the individuals in the low-fat control group.
The study took place in Spain and followed subjects between the ages of 55 and 80 for approximately five years. None of the subjects presented cardiovascular disease at the beginning of the study, but were at high risk for cardiovascular disease. Risk factors included diabetes, smoking, obesity, family history of cardiovascular disease, and hypertension.
During the study, subjects participated in quarterly education sessions, and depending on their group, received free olive oil or mixed nuts to supplement their meals. Subjects in the olive oil group were asked to consume at least four tablespoons of olive oil per day and participants in the nuts group were asked to consume at least one ounce of a mix of hazelnuts, almonds, and walnuts.
What is the Mediterranean diet?
The study defined a traditional Mediterranean diet as one characterized by a high component of olive oil, fruit, nuts, vegetables, and cereals. It also has a moderate component of fish and poultry, and small component of dairy products, red meat, processed meats, and sweets. The Mediterranean diet also includes drinking wine with meals in moderation. While it is high in fat, with nearly 40% of calories from fat, the Mediterranean diet is very low in saturated fats.
Participants in the Mediterranean groups were asked to eat between two to three servings of fruit and two to four servings of vegetables per day. They were also asked to consume at least three servings of fish and three servings of legumes per week. Those already accustomed to drinking wine with meals were asked to drink at least seven glasses per week. Mediterranean group participants were also asked to eat white instead of red meats and avoid commercially baked cookies and pastries as well as limit intake of processed meats and dairy products.
The Mediterranean diet group was encouraged to dress, stir-fry, and sauté vegetables in olive oil rather than steaming or using low-fat or fat-free spreads or dressings. Both Mediterranean groups were also counseled to substitute fat-free or low-fat processed snacks with a handful of nuts.
On the other hand, the control group was asked to follow a conventional low-fat western diet of fruits, vegetables, cereals and low-fat dairy products. However, while apparently most of the Mediterranean diet participants complied with the diet prescribed, few of the members of the control group actually stuck to the low-fat diet. For this reason the study ended up comparing a Mediterranean diet with the conventional western diet of commercially baked goods, soda, and red and processed meats.
An interesting conclusion that can be drawn from the study is that a low-fat diet may have little effect on reducing the risk of cardiovascular disease. Even though the participants in the Mediterranean groups did not lose weight, they did significantly reduce their risk for heart disease. This can be seen as good news, since it may be easier to incorporate certain foods into a diet than to eliminate fats altogether and lose weight. A diet that allows stir-frying and sautéing in olive oil sounds much easier to stick to than one where all vegetables are steamed or dressed in fat-free dressings.
The study was so successful that its data and safety monitoring board recommended it be cut short in 2011 because the results were so clear that it would be unethical to continue. Researchers cautioned, however, that the study has limitations, since participants were already at high risk for cardiovascular disease and already lived in a Mediterranean country, where it was easy to follow a Mediterranean diet. Further research is needed to determine how the results will apply to people with medium to low risk of heart disease and those who do not live in other parts of the world.
It is still unclear how and why the Mediterranean diet reduces the risk of heart disease. Researchers think that it is not as simple as adding nuts or olive oil to a diet, but rather it is the combination of foods and the amounts eaten that seem to have a beneficial effect on cardiovascular health.