Mediterranean Diet vs. low fat diet: which is better for prevention?

One of the early studies in the effects of a Mediterranean Diet on heart disease back in 2007  assessed the risk of a second coronary event within 30 days in those who had already been hospitalized for either a heart attack or unstable angina. The researchers found that a higher Mediterranean Diet score meant a 15% lower risk of heart attack, a 23% lower risk of dying during that initial hospitalization, and a 19% lower risk of any other cardiac event during those first 30 days.

In 2013 an analysis of participants in the Nurses' Health Study and the Health Professionals Follow-Up Study who had experienced a heart attack concluded that those who improved their diet the most (as measured by the Alternative Healthy Eating Index 2010, which is similar to a Mediterranean Diet) after their heart attack were 27% less likely to die of any cause and 19% less likely to die from a heart-related illness than those who did not improve their diet.

Today's research is also in those who were at greatest risk of a coronary event: those who had already experienced such an event (Lancet 2022;399:1876-85).

This study, performed in Cordoba, Spain, recruited about 1,000 men and women who had been hospitalized in the Reina Sofia University Hospital for a major cardiovascular event such as stroke, heart attack, or peripheral artery disease. They were randomly assigned to follow either a low-fat diet or a Mediterranean Diet.

Both groups received intense coaching and support from dietitians. Those following a low-fat diet were assigned to a goal of less than 30% total calories from fat (<10% saturated fat) and 55% of calories from carbohydrates. Those following a Mediterranean Diet consumed about 35% of their calories from fat (<10% saturated fat) and a maximum of 50% of calories from carbohydrates. Both diets aimed for about 15% of calories from protein.

The study lasted for 7 years, during which 132 patients abandoned their diets, although some allowed the study's authors to continue to monitor their health records until the end of the study. (Interestingly, nearly twice as many assigned to the low-fat diet quit the study as those who had been assigned to the Mediterranean Diet: 86 vs. 46.)

After taking into account the participants' age, family history of coronary disease, smoking status, and other variables, the authors found that for those whose diets matched their assigned diets at least 80% of the time, those who followed a Mediterranean Diet were 26% less likely to experience another coronary event than those who followed a low-fat diet. When the authors limited their analysis to only men, this climbed to 33%, although the authors note that there may not have been enough women in the study to be able to draw strong conclusions.

What this means for you

What's particularly interesting about this study is that the researchers found no significant difference between the two diets in their effects on cholesterol or glucose scores, which means the effects of the diet was not due to better metabolic scores alone. Add this study to the reasons to avoid a low-fat diet.