Tuesday, December 16, 2014

An overview of the Mediterranean diet



According to the Center for Disease Control, over 700,000 Americans have a heart attack each year. Finding ways to reduce the risk of heart disease is a part of the nation's public health agenda. Every few years, a flurry of new studies emerge to further our understanding of the potential health benefits associated with eating (and living) the Mediterranean way. I decided to spend this week writing about the Mediterranean diet. Before I get going, I want to mention that I hate the word “diet.” It implies something temporary in nature. When I talk about “diet,” I am referring to an eating plan; I am talking about a way of life

Where does interest in the Mediterranean diet originate?

The health, science, political and economic aspects of research and government have been aware of and interested in the Mediterranean diet for decades (1). The first formal epidemiological encounter with the Mediterranean diet dates back to 1948 when the government of Greece and the Rockefeller Foundation worked together to conduct a study to determine how to improve the living conditions on Crete. This was a comprehensive project and the Rockefeller Foundation sent an epidemiologist to Crete to lead the study. There were two main components of the dietary arm of project. One part was a 7-day weighed food inventory conducted at 128 homes. Another part of the study involved obtaining 7-day diet records from more than 500 people. The results of this study revealed that the people of Crete ate a largely plant-based diet that had a lot of nuts, olive oil, fruits, vegetables and legumes, but did not eat a lot of red meat or refined sugar. It also showed that the people of Crete had a lower incidence of cardiovascular disease.

In the 1950s, a man named Ancel Keys became intrigued by the fact that people with access to money living in United States also had access to plenty of food (1,2). In the U.S., people with money and access to food also had higher rates of heart disease and this phenomenon was not observed in some regions along the Mediterranean Sea. He postulated that a combination of lifestyle and diet impacted the risk of cardiovascular disease for the population as well as at the individual level and that there were biological measures that related to the risk of disease (i.e. cholesterol). This was a landmark study upon which our dietary guidelines were built. His research group published the first of their results in the 1950s. He published a heart-healthy cookbook in 1959. The dietary recommendations that Ancel Keys made in 1959 regarding diet, lifestyle and heart health are remarkably similar to the Dietary Guidelines for Americans that have been in place and slightly modified since 1990. 

Resources:
1) Nestle, M. (1995). Mediterranean diets: historical and research overview. AJCN. 61(suppl):1414S-20S.

2) Widmer R.J. Flammer AJ, Lerman LO, Lerman A. (2014) Mediterannean Diet, its components, and cardiovascular deisease. Am J Med. 10.1016/j.amjmed.2014.10.014. [Epub ahead of print].


The Mediterranean Diet in a Nutshell

The Mediterranean diet is rooted in fresh fruits and vegetables, whole grains, legumes, olive oil, nuts, and fish. Lifestyle factors that are essential components of what we refer to as the “Mediterranean diet” include regular physical activity and sharing mealtime with friends and family. This way of eating is a healthy and reasonable lifestyle approach that works for many people in non-Mediterranean countries.


By Daniel Schwen (Own work) [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

Make fresh or minimally processed plant based foods the main course at every meal (this usually refers to 6 servings a day).
o   fruits;
o   vegetables;
o   whole grains (breads, pastas, etc.);
o   and/or legumes (lentils, beans, peas).
Use olive oil in place of butter and margarine.
o   Olive oil contains monounsaturated fatty acids (MUFAs) that are heart-healthy. Select “extra virgin” or “virgin” olive oil to get the most MUFAs from olive oil.
o   Canola oil is also a good choice. It is also a plant-derived oil that contains unsaturated fats.
o   Butter contains saturated fat. Margarine may contain trans saturated fats. These fats are limited in the Mediterranean style of eating.
Enhance the flavor of food with herbs and spices.
o   Instead of seasoning with salt, the flavor of food is enhanced by using herbs and spices.
o   Herbs and spices not only add flavor, but they also add very small amounts of beneficial phytochemicals (plant chemicals) to the food you eat.
Eat fish at least 2 times a week.
o   Choose fatty fish like albacore tuna, salmon, lake trout, mackerel, herring, etc. because these types of fish have a type of polyunsaturated fat (PUFA) called omega-3 fatty acids. Omega-3 fatty acids are heart-healthy.
Incorporate lean proteins into your diet and use moderation.
o   Lean protein refers to poultry, eggs, low-fat or fat free dairy (yogurt, cheese, milk, etc.).
Limit your intake of red meats and sweets to only a few times a   month.
o   Try fruit-based dessert options
Regular physical activity is a part of daily life.
o   30 minutes per day 5-6 days a week of moderate (lower intensity) activity or 20 minutes per day 3 times a week of vigorous activity
Enjoy meals with friends and family.

Consult with a health care provider before starting a new exercise program. If you have a medical condition like diabetes, heart disease, high blood pressure, or anything else, it is important to discuss potential changes to your way of eating with your health care provider before you make them.

Resources


The Mediterranean Diet & Heart Health

Scientists like to know how things work. In nutrition, we like to know how dietary components impact biological function. Unfortunately, it is complicated.

Let’s say you eat an apple. Is it a red or green apple? This matters because the pigment of the skin contains phytochemicals (plant chemicals) so red apples have different phytochemicals than green ones. Not better or worse, just different. Apples also contain vitamins, fiber, water, carbohydrates, a little bit of protein and some minerals. You take a bite of the apple. You chew it and then swallow. It enters your stomach and small intestine where you digest and absorb it. You absorb nutrients and phytochemicals into your body. Scientists continue to learn about how phytonutrients function in the body. Many are involved in initiating cell signaling processes that lead to other functions like reducing inflammation. The carbohydrate portion of the apple helps to fuel your cells. You can use the amino acids released from the protein to make other proteins in your body. The microbiota (the microorganisms that live in your intestines) may make use of some of the components of the apple. The fibrous parts of the apple move on through to your colon and eventually get excreted. This can all happen after eating an apple because all of the components are ingested at one time and work together both in your food and in your body. This complex interaction gets lost when you take a supplement. 

It is possible that the complex interaction between the different components of the Mediterranean diet get lost when the diet and lifestyle is picked apart and taken out of context. To prepare for this post, I read some review and primary research articles (I reference a recent review article throughout this post). In general, individual healthful effects of fruits and vegetables, fish, olive oil, whole grains, nuts, physical activity and red wine (in moderation) are identified, however, different studies find different results. This may be because researchers look at different outcome measures, because of other differences in study design, or it may be because taking one constituent out of context modifies the effect of its interaction with the other dietary and lifestyle components that are part of the Mediterranean diet. 


Diets rich in olive oil and fatty fish provide MUFAs and PUFAsThese fatty acids may reduce inflammation in the body, decrease the amount of oxidative damage, and reduce the risk of blood clotting. Extra virgin and virgin olive oil contain MUFAs which have been shown to reduce LDL cholesterol, reduce blood clotting, decrease reactive oxygen species (which can cause oxidative damage). Fatty fish contain omega-3 PUFAs which improves lipid profiles (reduce LDL cholesterol) and improve blood pressure (1, 2). Canola oil is another source of PUFA that is also heart-healthy. It has been shown to reduce triglycerides and lower blood pressure when used instead of saturated fat (2).

Fruits and vegetables contain vitamins, phytochemicals and fiber. Diets that are high in fruits and vegetables may improve cholesterol levels and reduce the presence of reactive oxygen species. People who eat more fruits and vegetables tend to eat them in place of other foods. Eating more fruits and vegetables is associated with a decreased risk for cardiovascular disease. It may also be associated with lower blood pressure and lower body mass index (1). The maximum benefits of the Mediterranean diet are associated with 6 servings or more per day of fruits and vegetables, but a moderately reduced risk of cardiovascular disease has been, in some observational studies, detected with 3-5 servings per day (2).

Whole grains provide fiber and phytochemicals. Eating whole grains is associated with better health and a reduced risk of heart disease. Whole grains provide fiber. Fiber facilitates removal of waste from the colon and also reduces the absorption of some types of dietary compounds, like dietary cholesterol. Diets that meet the fiber recommendation (25 grams/day women and 35 grams/day men) tend to be associated with less overall inflammation, healthier blood pressure, and improved cholesterol.

Nuts and legumes are an important part of the Mediterranean diet. Nuts contain unsaturated fats and are high in calories (they provide 9 kcals/gram). Because they are both a healthful choice but calorically rich, it is recommended that you eat them with awareness and substitute them for another food such as a food that contains saturated fat. Eating nuts is associated with reduced risk of cardiovascular disease, improved lipid profiles and better blood pressure (1). Legumes are a staple in the Mediterranean diet, however it is unclear how they work in the body to improve health (1). 


"Broad-beans-after-cooking". Licensed under Public Domain via Wikimedia Commons 
(Fava beans)





The health benefits of drinking red wine, in moderation. Drinking red wine may improve cholesterol, lower blood pressure and reduce the risk of cardiovascular disease (1,2). Moderate alcohol consumption of wine means one 5-oz glass of wine per day for women and men over 65 and two 5-oz glasses of wine per day for men (2). Phytochemicals present in the skin of red grapes (i.e. resveratrol) are believed to be responsible for the health benefits of red wine. It is possible to achieve similar benefits with red grape juice, but it is important to select juice that is low in added sugar.

If you are concerned about heart disease, have a pre-existing health condition, or a family history of heart disease, it is important that you discuss your concerns with your health care provider before starting a new eating plan and/or exercise program

Resources:

1) Widmer R.J. Flammer AJ, Lerman LO, Lerman A. (2014) Mediterannean Diet, its components, and cardiovascular deisease. Am J Med. 10.1016/j.amjmed.2014.10.014. [Epub ahead of print].


2) Mayo Clinic Staff (last update on June 14, 2013). "Mediterranean diet: A heart-healthy eating plan." Mayo Clinic. Accessed 12/15/2014.


Final Thoughts

For many people, the Mediterranean diet is a healthy lifestyle choice. Current research efforts regarding the Mediterranean diet continue to focus on understanding the health benefits of it. In particular, a branch of research in this area is interested in if/how the Mediterranean diet impacts the brain. I suspect we will learn more about the role of the Mediterranean diet and whether or not it is helpful in the prevention of Alzhemier disease and other forms of dementia in the months and years to come.