Now let's look at the details of the study. This was a multi-center study in Spain that enrolled 7447 people, both men and women ages 55 to 80 years old. None the participants had detectable heart disease at the beginning of the study, but they were all at high risk for developing heart disease. They either had type II diabetes or at least three of the following risk factors: smoking, hypertension, elevated LDL, low HDL, overweight, or a family history of premature heart disease.
The participants were divided into three groups. A Mediterranean diet +1.7 oz of extra virgin olive oil each day, a Mediterranean diet +30 nuts each day (15 walnuts, 8 hazelnuts and 7 almonds), and a traditional low-fat diet. (The participants in the Mediterranean diet groups were provided with the extra olive oil or nuts to assure adherence). There was no restriction on calories or encouragement to exercise. At the end of five years both versions of the Mediterranean diet resulted in a 30% reduction in cardiovascular events, primarily stroke, compared to the control diet.
So what does this mean for you?
1) This study is consistent with many other studies showing that the Mediterranean diet is a healthy diet. In case you were wondering, a Mediterranean diet is characterized by a high intake of olive oil, fruit, nuts, vegetables and cereals; a moderate intake of fish and poultry; and a low intake of dairy products, red meat, processed meats, and sweets. It generally also includes wine in moderation, consumed with meals.
2) What about low-fat diets? Are they also good for you? As I said above, low-fat diets have been shown to be effective at preventing a heart attack for highly motivated people who have already had a heart attack, but they have not yet been shown to be effective in a primary prevention setting such as the study I just described.
That may be because it is difficult to get good adherence to low-fat diets in a large clinical study such as this one where the participants may not be highly motivated to make major changes to their diet. For example, some of the headlines describing the results of this study go so far as to say that it shows the Mediterranean diet is effective and a low-fat diet is ineffective. That would be a misinterpretation of the data. The group assigned to the low-fat diet had very poor adherence to the diet. In fact, their intake of fat changed very little.
Perhaps this was because the study was conducted in Spain where a Mediterranean diet is much more familiar than a low-fat diet. But the group on the low-fat diet in this study also had much less dietary counseling than the groups on the Mediterranean diet. The groups on the Mediterranean diet attended dietary training sessions at the beginning of the diet and four times a year thereafter to assure adherence to the diet. The group assigned to the low-fat diet attended dietary training at the beginning of the diet and were then just given a leaflet explaining how to follow a low-fat diet for the first 3 years of the study.
To Your Health!
Dr. Stephen G Chaney
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.