Monday, February 1, 2016

Mediterranean Diet: The Best Ever?

by Larry Creswell, M.D.

Can a diet with more fat really be healthier for your heart? Well, it may be true! Let’s talk about a recently published scientific report on the Mediterranean diet and heart health. The findings are remarkable and have implications for athletes and non-athletes, alike.

What is the Mediterranean Diet?
First, we should take a moment to discuss just what we mean by the Mediterranean diet. As you may know, some 20 countries and four territories in Europe, Africa, and Asia border the Mediterranean Sea, but we’re talking here about the diet most commonly associated with Greece, southern Italy, coastal Spain, and perhaps Crete. Unfortunately, though, there is no formal definition.

Although it was recognized much earlier, the term “Mediterranean diet” was popularized in the mid-1990s by Walter Willett, MD, DrPH, an expert in nutrition at the Harvard School of Public Health. He is best known for his best-selling book, Eat, Drink, and Be Healthy, but he also gave us the widely accepted notion of the Mediterranean diet. To quote from the scientific study we’ll detail below, it includes “a high intake of olive oil, fruit, nuts, vegetables, and cereals; a moderate intake of fish and poultry; a low intake of dairy products, red meat, processed meats, and sweets; and wine in moderation, consumed with meals.” Fats may represent up to 35% of total calories in this diet, with saturated fats accounting for less than 8% of total calories.

The Mediterranean Paradox
What’s interesting is that the Mediterranean populations consume a diet that is relatively high in fat intake yet enjoy much lower rates of coronary heart disease than populations. This benefit is thought to be due to the types of fat in the diet -- low quantities of saturated fats and high quantities of monounsaturated fats. Check out a primer by the American Heart Association on the various types of fat.

But we also know that this Mediterranean population has a lifestyle that includes ample physical activity, consumes their big meal of the day in the afternoon, often naps and gets plenty of sunshine. A better diet is probably not the only reason this population avoids heart disease.

The New Study
Now comes a new study -- the PREDIMED trial -- reported in the March 5, 2013, issue of the prestigious New England Journal of Medicine from a group of investigators in Spain. They studied 7447 individuals aged 55-80 who had no known cardiovascular diseases at the time of enrollment but who had risk factors for the development of cardiovascular disease (such as diabetes, smoking, high blood pressure, elevated lipid/cholesterol levels, family history of heart disease, and obesity). The subjects were divided into three groups who ate different diets:

  1. A Mediterranean diet supplemented with extra-virgin olive oil -- 1 liter per week
  2. A Mediterranean diet supplemented with mixed nuts -- 30 g per week
  3. An American-style low-fat diet

Except for their diet, the three groups were very similar in other respects.

This is the largest study of this sort -- ever. Despite the long history of promoting low-fat diets in this country, there has never been a similar study to test the value of that advice.

Here, the subjects were monitored for the development of cardiovascular problems using a combined, composite endpoint of myocardial infarction (MI), stroke, or death from cardiovascular (CV) causes. After a median follow-up period of 4.8 years, the study was terminated by a review board because an interim analysis showed such a marked difference in outcome between the treatment groups. The review board felt that it was unethical to continue the study if the investigators knew that one or more of the diets were clearly superior.

As it turned out, significantly fewer episodes of MI, stroke, or death due to CV causes occurred in the groups eating either of the Mediterranean diets. The magnitude of this beneficial effect of the Mediterranean diet was substantial, with perhaps as much as a 30% reduction in the adverse outcomes. That’s a huge effect.

This study has received a lot of attention in the popular press. The Mediterranean diet has been described as the “best ever” and said to “rock the medical world.” And advocates have encouraged nearly everyone to adopt this diet.

What are the Lessons?
There are a few important take-home points from the study:

  • The traditional American-style low-fat diet is obviously not good. The study calls into question the conventional wisdom favoring this dietary approach.

  • The inclusion of healthy fats in the diet may well be one approach -- along with physical activity, etc. -- to reduce one’s cardiovascular risk.

  • The Mediterranean diet is practical and achievable. The study subjects assigned to the Mediterranean diets actually had much better compliance compared to those in the low-fat diet group.

A Couple Caveats
Before we conclude that the Mediterranean diet is truly the best diet for everybody, though, we should keep in mind a couple important issues with the new study.

The study enrolled older individuals with moderate risk for the development of heart disease. We might reasonably conclude that benefits would be less likely to accrue in younger individuals who did not have these risk factors. Many healthy athletes would be in this category.

The study subjects were all Mediterranean. Whether the beneficial results can be realized in other populations remains unknown.


Larry Creswell, M.D., is a cardiac surgeon and Associate Professor of Surgery at the University of Mississippi Medical Center in Jackson, Mississippi. In addition to his regular column on Endurance Corner, he maintains The Athlete's Heart blog to offer information about athletes and heart disease in an informal way and to encourage exchange and discussion that will help athletes build a heart-healthier lifestyle. You can contact him at lcreswell@umc.edu.
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