A Heart-Healthy Mediterranean Diet?

Mediterranean diets led to lower risk of heart attacks and strokes in Spanish trial

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) You might have heard about the Mediterranean diet. It involves eating certain specific "healthy" fats and less processed carbohydrates. It might also help stave off heart disease.

A recent study compared individuals eating Mediterranean diets with those eating low fat diets. Fewer heart attacks, strokes and heart-related deaths occurred in the Mediterranean group than in the low fat group.

There were several limitations to the study, but it still appears to show a slightly lower risk of heart disease among those eating the Mediterranean diet.

"Ask your doctor about the Mediterranean diet."

The study, led by Ramón Estruch, MD, PhD, of the Center for Biomedical and Pathophysiology Research of Obesity and Nutrition, aimed to see whether a Mediterranean diet might reduce the risk of heart disease.

The researchers conducted a trial with 7,447 individuals, aged 55 to 80, who were at high risk for heart disease but had not yet developed it when the study began.

The participants were determined to be at high risk for heart disease because they either had type 2 diabetes or else they had at least three of the following risk factors for heart disease:
    •    smoking
    •    high blood pressure
    •    high low-density lipoprotein cholesterol levels
    •    low high-density lipoprotein cholesterol levels
    •    overweight or obesity
    •    family history of premature coronary heart disease

The study participants were split into three groups that each ate a different diet. One group, which ended up with 2,543 participants, ate a Mediterranean diet supplemented with extra virgin olive oil. They were provided the olive oil for free during the study.

Another group, which included 2,354 participants by the end of the study, ate a Mediterranean diet supplemented with mixed nuts, which they received for free during the study.

The third group, with 2,450 participants, ate a diet of their choice with the recommendation to reduce their dietary fat. This group received small nonfood gifts during the study.

Recommended items in the Mediterranean diet include olive oil, tree nuts and peanuts, fresh fruits, vegetables, fatty fish, seafood, legumes, white meats and optional wine with meals. Discouraged items include soda drinks, commercial bakery goods, sweets, pastries, spread fats and red and processed meats.

Those in the low fat diet group were recommended to eat low-fat dairy products, bread, potatoes, rice, pasta, fresh fruits, vegetables, lean fish and seafood. They were discouraged from eating vegetable oils (including olive oil), commercial bakery goods, sweets, pastries, nuts, fried snacks, red and processed fatty meats, visible fat in meats and soups, fatty fish and spread fats.

Those in the Mediterranean diet participated in individual and group educational sessions four times a year during the study, which tracked individuals for an average of just under five years each.

For the first three years, the control group did not receive personalized diet advice or group sessions. They received only an annual leaflet explaining the low fat diet. They did have the same group and individual educational sessions during the last two years of the study.

The researchers tracked how many participants had a heart attack, a stroke or died from heart-related causes. A total of 288 participants had one of these three things occur during the course of the study, between October 1, 2003 and December 1, 2010.

Those assigned to Mediterranean diets, whether with extra olive oil or extra nuts, adhered well to their diets, based on their reports of their food intake and on blood analysis.

During the study, 96 heart attacks, strokes or deaths from heart-related causes occurred in the group eating a Mediterranean diet with extra virgin olive oil. This translated to a rate of approximately 8.1 events per 1,000 people per year.

Meanwhile, 83 heart attacks, strokes or cardiovascular deaths occurred in the group eating a Mediterranean diet with extra mixed nuts. This translated to a rate of approximately 8 events per 1,000 people per year.

In the control group not assigned to a Mediterranean diet, a total of 109 heart attacks, strokes or cardiovascular deaths occurred during the study. This translated to a rate of approximately 11.2 events per 1,000 people per year.

Approximately one more heart attack per 1,000 people per year occurred in the low fat diet group than in the Mediterranean diet groups. Approximately 2 to 3 more strokes per 1,000 people per year occurred in the low fat diet group than in the Mediterranean diet groups.

The rate of heart-related deaths was nearly identical between the low fat diet group and the group eating the Mediterranean diet with extra nuts. This rate (3 deaths per 1,000 people per year) was one more than the rate of those eating the Mediterranean diet with extra virgin olive oil.

The researchers calculated that those eating the Mediterranean diets were approximately 30 percent less likely to experience one of the events tracked (heart attack, stroke or cardiovascular death) than those eating the low fat diet.

This risk reduction means that, over the course of the study, about 3 fewer people eating one of the Mediterranean diets experienced a heart attack or stroke or cardiovascular death each year than those eating the low fat diet experienced.

"We observed that an energy-unrestricted Mediterranean diet, supplemented with extra virgin olive oil or nuts, resulted in a substantial reduction in the risk of major cardiovascular events among high-risk persons," the authors wrote. "The results support the benefits of the Mediterranean diet for the primary prevention of cardiovascular disease."

Aside from the change in the diet advice to the low fat diet group halfway through the study, another limitation of the study was that the participants all lived in a Mediterranean country. It's therefore unclear if individuals at high risk for heart disease in other countries would see the same benefits from switching to a Mediterranean diet.

Sarah Samaan, MD, a cardiologist with Legacy Heart Center in Dallas-Fort Worth and a dailyRx expert, said she was impressed with this study.

"The diet advice and recommended foods were completely attainable, and the diets recommended included foods that are easy to find and relatively inexpensive," Dr. Samaan said.

"All three groups received good advice and support, and so the study does not compare the Mediterranean diet to a typical US diet, heavy on the fast food and processed food," she said. "I suspect it would have come out way ahead had that been the case. In addition, the study was conducted in Spain, where baseline diet quality is probably substantially healthier than in the US."

Dr. Samaan said the number of cardiovascular events might even have been higher in the low fat diet group had fewer of those participants dropped out. She also noted that there were fewer heart attacks across all three groups than expected, which made it more difficult to statistically calculate the different risks across the groups.

"Other studies have also found good support for a Mediterranean diet as well as for a diet rich in nuts and olive oil, but this study puts the diet to the test in people without heart disease at baseline," Dr. Samaan said.

"For years, well-meaning doctors have recommended that patients eat 'low fat,' but our understanding of what is heart healthy has evolved far beyond that outdated advice," she said. "We know now that certain fats, especially the monounsaturated and omega-3 fats, are critical for optimal heart health, and this study confirms that choosing these types of fats can have an important impact on our health and well being."

The study was published February 25 in the New England Journal of Medicine. The research was funded by the Spanish government, the Carlos III Institute of Health, the Center for Biomedical and Pathophysiology Research of Obesity and Nutrition, the National Center for Cardiovascular Resesarch, the Foundation for Health Research-European Foundation of Regional Development, the Ministry of Science and Innovation, the Mapfre 2010 Foundation, the Health Council of the Government of Andalucia, the Public Health Division of the Department of Health of the Autonomous Government of Catalonia, the Generalitat Valenciana and the Regional Government of Navarra.

Seven of the authors reported financial ties (research, honoraria, speaker fees, boards or travel funding) to a number of pharmaceutical companies, food companies and food industry groups, such as PepsiCo, the California Walnut Commission, Nestle and Danone.

Reviewed by: 
Review Date: 
February 24, 2013
Last Updated:
August 15, 2013