Let's take a look at the Mediterranean diet. The bulk of the food in Mediterranean countries comes from fruits, vegetables, seeds, nuts, and whole grains that are consumed daily. And when I say whole grains, I mean in their whole form. For example, whole wheat bread that you typically find in the supermarket is not made from whole grains. It has been milled to a point where it's too process and ends at being digested just like other process-baked goods.
Next, you have fish and sea food which are consumed at least twice a week. There is a moderate amount of dairy, poultry and eggs and very rarely sweets. They also don't drink soft drinks and juices but, rather, water and red wine in moderation.
We have known for a long time from epidemiological studies that people living in the Mediterranean countries have less heart disease and strokes. The first trial to specifically study the effect of the Mediterranean dietary intervention was the PREDIMED Study. This was a large randomized primary prevention trial of about 4,000 people. Patients who were randomized to Mediterranean diet, supplemented with extra virgin olive oil, Mediterranean diet supplemented with nuts and regular low fat diet. People randomized to the olive oil group were recommended to have at least four tablespoons of oil a day. Whereas subjects randomized to the nut group who were recommended to eat at least three servings of nuts per week.
Everybody was to eat daily at least three servings of vegetables, two servings of fruit, and weekly three servings of fish and seafood, especially fatty fish. Three servings of legumes and to favor white meat instead of red meat. In the low-fat group, subjects were recommended to eat a similar amount of fruits and vegetables as a Mediterranean diet as well as fish and seafood. They were also encouraged to eat low-fat dairy products and to have carbs like bread, potatoes, pasta and rice. They were discouraged from eating nuts and fat that were visible on meats or in spreads. The PREDIMED Study was a landmark study. And it was seminal because it was the first study to systematically study an intervention using the mediterranean diet. This study showed an overall decrease in the risk of disease in the groups that were supplemented with extra virgin olive oil or nuts compared to the low-fat diet. It showed not only an improvement in cognitive function, but it also showed a marked decrease in vascular disease. The change was largely driven by strokes, specifically.
The PREDIMED Study also showed an improvement in depression scores, especially in the group that was supplemented with nuts. And this effect was seen more strongly in patients that had diabetes. Recall the association between insulin resistance and depression. The Mediterranean diet supplement with nuts is associated with improved depression. The SMAS trial was specifically designed to study the effect of a Mediterranean diet on depression. It compared diet to social support in the treatment of depression. In this study, 67 patients were randomized. Diet consisted of a Mediterranean dietary pattern with fruits, veggies, beans and legumes, non-sweetened dairy, and seafood. The control group met with a clinician at the same frequency as the diet intervention group and had support and talk therapy.
At the end of three months, the Mediterranean diet group saw a decrease in depression by 32% compared to 8% in the social support group. The number needed to treat our NNT was four. That is an amazing effect size and the more adherent patients were with the diet, the better their depression improved.