Mediterranean Diet Revisited

By Paul E. Lemanski, MD, MS, FACP

Editor’s Note: This is the 123rd in a series on optimal diet and lifestyle to help prevent and treat disease. Any planned change in diet, exercise or treatment should be discussed with and approved by your personal physician before implementation. The help of a registered dietitian in the implementation of dietary changes is strongly recommended.

Medicines are a mainstay of American life and the healthcare system not only because they are perceived to work by the individuals taking them, but also because their benefit may be shown by the objective assessment of scientific study. Clinical research trials have shown that some of the medicines of Western science may reduce the risk of Type 2 diabetes, heart attacks, strokes, cardiovascular death and even some cancers.

In the first 122 installments of the Non-Medicated Life, a healthy diet and lifestyle have been shown to accomplish naturally for the majority of individuals most of the benefits of medications in the prevention of the chronic medical conditions mentioned above. With respect to a healthy diet the Mediterranean diet is widely regarded in medical and nutrition circles as one of the healthiest. This diet is still eaten in many parts of the countries bordering the Mediterranean sea, but a recent influx of the “standard American diet” has diluted many of its benefits. Moreover, Mediterranean restaurants in the U.S. many times do not strictly adhere to the diet’s original tenets. In this article I would like to more completely define the Mediterranean diet, describe its most beneficial aspects, and suggest how the diet works to so impressively improve health.

First, how can we define a Mediterranean diet? For thousands of years humans inhabiting the lands surrounding the Mediterranean sea have had the foods eaten determined by the animals and plants found in this region, which in turn have been determined by the land’s geography and climate. For example, cattle are not found in large numbers due to lack of available grasslands. Consequently, red meat consumption is naturally restricted in favor of smaller animals such as chickens, ducks, and seafood and this has influenced the overall diet composition. Dairy is generally limited to yogurt and cheese. Examples of seafood includes salmon, sardines, oysters, mussels, shrimp and clams.

The lack of intensive animal husbandry has limited the number of animals sacrificed resulting in decreased overall consumption which in turn decreases both the size of portions and the frequency of consumption. Therefore, one important aspect that helps define the Mediterranean diet is restricted meat consumption, especially red meat. Meat is consumed no more than twice a week and with no more than four ounces in a serving.

Available plants also help to define the composition of the diet. You find a great diversity of vegetables including tomatoes, broccoli, cauliflower, carrots, Brussels sprouts, leafy grans, onions, garlic, eggplant and olives, the latter of which also supplies oil for cooking. There is also a variety of fruits such as apples, grapes, oranges, figs, dates, citrus, oranges, pears, peaches, avocado and melons. Berries of all types are also popular. Legumes are abundantly represented in the diet including beans, peas, lentils, and chickpeas. Nuts and seeds include walnuts, almonds, hazelnuts, pumpkin and sunflower seeds. Whole grains include whole wheat bread, whole wheat pasta, barely, oats, and quinoa. The emphasis is on fresh vegetables and fruits and the use of extra virgin olive oil as a replacement for  butter and lard; fruit is eaten for snack or dessert.

This diet would represent a significant change for most Americans currently eating the standard American diet or for those who frequent most Italian restaurants and consider pizza representative of this way of eating. That said, the Mediterranean diet within the bounds noted above is satisfying, has variety and balance, and should not be thought of as a diet, but rather a way of eating. Given the differences from the standard American diet, what is the evidence that making such a significant change would be worth the effort and actually improve health?

Strict adherence to such a diet has been shown in two randomized clinical trials, the PREDIMED study and the Lyon Diet Heart study, to reduce cardiovascular events such as heart attacks and strokes. The PREDIMED study from Spain was published in the New England Journal of Medicine. It randomized 7,447 people to one of three diets: a Mediterranean diet with extra-virgin olive oil, a Mediterranean diet with nuts, and a control low fat diet. The result was a 30% relative risk reduction in major cardiovascular events for those following a Mediterranean diet with extra-virgin olive oil or nuts as compared to controls. Given that statin drugs, the mainstay of cholesterol management, also reduce relative risk by 30%, this non-medicated result is impressive.

The Lyon Diet Heart study from France, published in the cardiology journal Circulation, randomized 605 patients who had a history of a heart attack to receive either a Mediterranean diet higher in plant based Omega-3 fats (alpha-linolenic fatty acid or ALA) vs. a “prudent” Western diet (healthier than a standard American diet). The result after five years was a 70% relative risk reduction for fatal and non-fatal heart attack – an astonishing result exceeding the benefit of medications. This raises the question of even greater benefit combining diet and medication. Alpha-linolenic fatty acid (ALA) is found in walnuts and canola oil. Perhaps the most interesting result was that the cholesterol levels in the Mediterranean diet group and the control group eating the “prudent” Western diet were the same at the beginning and at the end of the study. This suggests that the Mediterranean diet works by a non-cholesterol lowering mechanism and brings us to the last issue to be revisited, which is how does it work.

The Mediterranean diet is a predominately a whole food, plant based diet and this may be the primary mechanism reducing risk. Plant based fats from whole foods such as avocados, nuts, and seeds are predominately monounsaturated with increased omega-3 fatty acids (ALA) and their minimal processing preserves thousands of phytochemicals such as polyphenols and antioxidants, which are anti-inflammatory and reduce oxidation of plaque. Extra virgin olive oil is also effective from an antioxidant perspective. Thus while it appears that low levels of LDL cholesterol are protective from the perspective of cholesterol plaque formation, reduced oxidation of plaque (educed ox-LDL) is also important for plaque stabilization. 

It is significant therefore that plant foods have 64 times the amount of antioxidants than animal foods. Fruits are even more powerful, with berries averaging 10 times the antioxidant content of other fruits and vegetables. Mediterranean herbs and spices may have 10 times the antioxidant power of nuts and seeds. For example, a single teaspoon of dried oregano or 2/3 teaspoon of marjoram may double the antioxidant content of a bowl of whole wheat spaghetti with marinara. Such benefits appear not to occur with antioxidant supplements but require the presence of the whole food.

In summary, the Mediterranean diet described above is a non-medicated way of lowering cardiovascular risk rivaling medication. It is a predominately plant-based diet, which allows meat and fish with a somewhat restricted frequency of consumption, and in smaller amounts than most Americans are used to. As a consequence saturated fat is minimized. A variety of vegetables and fruits are eaten daily, providing antioxidants in their natural state. Extra-virgin olive oil, nuts, and seeds provide greater amounts of monounsaturated and omega-3 fats than in a typical American diet. Grains are minimally processed. Despite such seeming restrictions, the Mediterranean diet offers great variety, enjoyment, and sustainability. As such, the Mediterranean diet provides a valuable strategy for achieving the non-medicated life.

Paul E. Lemanski, MD, MS, FACP (plemanski3@gmail.com) is a board-certified internist practicing internal medicine and lifestyle medicine in Albany. Paul has a master’s degree in human nutrition, he’s an assistant clinical professor of medicine at Albany Medical College, and a fellow of the American College of Physicians.