May 2019 Issue
The Mediterranean Diet
By KC Wright, MS, RDN, LD
Vol. 21, No. 5, P. 18
Learn why it’s ranked the number one dietary pattern of the year and the keys to implementation.
The confetti and streamers strewn from ringing in the 2019 New Year had barely been swept up when U.S. News & World Report announced their Best Diet rankings to the eager ears of the estimated 45 million Americans who diet annually. The Mediterranean diet (MedDiet) made its debut as the Best Diet Overall this year, bumping out the Dietary Approaches to Stop Hypertension (DASH) diet, with which it was tied for the top spot in 2018.1
The MedDiet is characterized by its relatively high fat intake from olive oil, which makes it palatable yet low in saturated fat and high in nutrients and dietary fiber. It’s a diet that’s rich in antioxidant compounds and bioactive elements with anti-inflammatory effects, and it has a low glycemic index.2 The MedDiet is broadly acknowledged by many health professionals to offer a host of health benefits, and the scientific research continues to be consistent in showing the diet’s effect in reducing chronic disease and mortality. This article reviews the apparent unparalleled science that raises the MedDiet to its crowning status, and practical application for dietitians when communicating the eating pattern to clients and patients.
Report Ranking Methodology
To calculate the diet rankings, U.S. News & World Report convened a panel of 25 nationally recognized experts comprising health professionals, including nutritionists and specialists in diabetes, heart health, human behavior, and weight loss. U.S. News editors and reporters sifted through medical journals, government reports, and other resources to develop detailed profiles for their diet roster. Each diet profile illustrated how the diet works, analyzed claims for validity, identified possible health risks, and demonstrated the practical aspects of following the diet.
Through an in-depth survey, as well as their own fact finding, each expert scored 41 eating plans in nine categories, such as ease of compliance, likelihood of losing significant weight in both the short and long term, and effectiveness against CVD and diabetes. To standardize the ratings, the experts established a set of health definitions and values for each category. Neither cost nor the influence of exercise was factored into the diet rankings. Experts also were solicited to provide their own advice for someone considering a particular diet. Any expert who indicated a clear or apparent conflict of interest with any particular diet abstained from rating that diet.
Once each diet was thoroughly reviewed, the experts’ ratings were converted to scores from highest (5) to lowest (1). Those scores were then used to construct nine sets of Best Diets rankings—Overall, Commercial, Weight-Loss, Diabetes, Heart-Healthy, Healthy Eating, Easiest to Follow, Plant-Based, and Fast Weight-Loss. The U.S. News & World Report ranks the MedDiet the Best Diet Overall with a comprehensive score of 4.2/5, including a score of 3/5 for weight loss and 4.9/5 as a healthful diet. The MedDiet narrowly edged out the DASH diet, which was ranked overall at 4.1/5.
Why the MedDiet?
According to Eric Rimm, ScD, a professor of epidemiology and nutrition director of the cardiovascular epidemiology program at the Harvard School of Public Health, and a panel expert for U.S. News & World Report Diet Rankings, both the MedDiet and the DASH diet “are great, but the evidence and number of studies for the MedDiet are much greater.” Rimm explains, “For chronic disease prevention, the MedDiet has been tested and proven to reduce the risk of cardiovascular disease, diabetes, and other chronic conditions in a randomized setting—something the DASH diet has not been equally as well tested. The MedDiet is likely better, as indicated by the evidence base available.”
In the current context of assessing the health effects of overall food patterns instead of single nutrients or foods, the MedDiet has become a scientific topic of high interest due to evidence that has directly supported substantial health benefits, including some large trials with hard clinical endpoints that aren’t available for any other dietary pattern.2 David L. Katz, MD, MPH, FACPM, FACP, FACLM, founding director of Yale-Griffin Prevention Research Center and a member of the expert panel of U.S. News & World Report Diet Rankings explains his view on the elevated MedDiet status: “I think one factor is that there have been a number of recent research papers on the Mediterranean diet, so it is front of mind. The Mediterranean diet has certainly stood the test of time, contributing to the health of populations across many generations.”
Although WW (formerly Weight Watchers) continues to hold the top spot for Best Weight-Loss Diets in U.S. News & World Report 2019 rankings with a 3.9/5, research shows improved weight outcomes for individuals following the MedDiet. Data from PREDIMED—a primary prevention trial involving thousands of people with diabetes or other risk factors for heart disease—showed that a MedDiet supplemented with extra virgin olive oil or nuts, and without any fat and calorie restrictions, decreased bodyweight and resulted in less gain in central adiposity compared with a control diet.3 Participants in the olive oil group lost the most weight. In a study of more than 1,000 teenagers, researchers tested a six-month school-based nutrition education intervention based on the principles of the MedDiet and found significant decreases in overweight and obesity, abdominal obesity (specifically waist circumference), and blood pressure.4
Hands down, the MedDiet is heart-healthy. Evidence consistently has shown reduced risk of CVD and overall mortality.5,6 In fact, no other food pattern is backed by an accrual of sound prospective epidemiologic and trial-based evidence supporting the reduction in clinical CVD events.2 And, as Rimm confirms, “We are all about an evidence base.”
Data from the Women’s Health Study on 26,000 healthy subjects demonstrated that those who followed a MedDiet had 25% less risk of developing CVD over 12 years.7 The reduction was attributed to changes in inflammation, blood sugar, and BMI.
The MedDiet plan helps to dispel the myth that people with, or at risk of, CVD should follow a low-fat diet. In the PREDIMED research,3 total fat intake was a hefty 39% to 42% of the diet, much higher than the 20% to 35% fat guideline set by the Institute of Medicine.8
What’s more, research shows the MedDiet helps to prevent and control type 2 diabetes. A study based on dietary and diabetes data from more than 22,000 people over 11 years found that those who adhere to a MedDiet may have a lower risk of developing type 2 diabetes compared with those who don’t follow the eating style.9 A meta-analysis of four cohort studies with more than 15,000 cases of type 2 diabetes found that those consuming the most olive oil had a 16% lower risk of developing the condition.10 In fact, every two-teaspoon increase in olive oil daily was linked with a 9% lower disease risk.
For patients with established type 2 diabetes, adding olive oil to the diet significantly lowered their HbA1c.10 Risk of type 2 diabetes was reduced in the PREDIMED trial.11 A systematic review of the MedDiet to determine its effect for a year showed that participants with type 2 diabetes saw better improvements in blood sugar control on the MedDiet compared with those following a low-fat, low-carbohydrate diet.12
Like most diets, the cost of the MedDiet depends on how and where the food is sourced and prepared—whether ingredients are bought in bulk, for example, or whether most meals are consumed in upscale restaurants. Shopping for whole foods and preparing them at home does take more time and effort, but it’s often much more affordable. Good extra virgin olive oil, nuts, fish, and fresh produce can be more expensive than highly processed convenience foods that are high in calories, sodium, sugar, and unhealthful fats.
Yet, it’s also important to consider how diets and eating patterns may have an effect on expenses beyond food. To determine the influence of more healthful eating on health care costs, researchers analyzed the relationship between diet, health problems, and health care spending. Preliminary data suggest that if Americans were to make their diets just 20% more Mediterranean, the United States would save $25.7 billion per year—significant savings with a realistic shift in diet quality. If Americans shifted their eating patterns to consist of an 80% MedDiet, an estimated $135 billion per year savings would occur.13
Implementing the MedDiet
The 2015–2020 Dietary Guidelines for Americans already have taken steps toward adapting the MedDiet for the American population.14 RDs have an opportunity to share the foundation of the 2019 U.S. News & World Report Diet Rankings to reinforce the benefits of the MedDiet with their clients and patients. Margaret Slavin, PhD, RD, an associate professor of nutrition and food studies at George Mason University, says, “I think of the U.S. News [diet] rankings as a way for the experts (who are deeply familiar with the evidence base) to communicate the merits and drawbacks of these diets with the public.”
When dietitians introduce or reaffirm the MedDiet, it’s important to communicate that there’s no “one” MedDiet; rather, it reflects an eating pattern of traditional diets of countries bordering the Mediterranean Sea before the mid-1960s—before globalization had its influence on lifestyle, including diet.2 The traditional diets differ slightly among the Italians, Greeks, Spaniards, and French as a way of eating, given their cultures and food values. Yet, they all share many of the same principles—a relatively high total fat intake (from olive oil) that makes it palatable, but low in saturated fats (by limiting meat products), and rich in nutrients and dietary fiber from a plethora of vegetables, fruits, nuts, legumes, and whole grains. Consumption of fish along with the option of red wine for adults at meals, and low to moderate intake of dairy round out the diet. In addition to adapting the MedDiet as a regular meal pattern, complementary traditions emphasized the beneficial social aspects of eating meals together and active lifestyles.
“I think another important factor is how much this is not a ‘diet,’“ Katz says. “It is, instead, a way of eating native to a whole region. I suspect my fellow expert panelists share my view that ‘dieting’ is much less desirable than eating well permanently.” In fact, the Greek word for diet, diaita, means way of life or lifestyle, a set of skills, knowledge, rituals, symbols, and traditions, ranging from the landscape to the table.15
For many clients and patients, the not-so-structured MedDiet can be a challenge to determine what to eat and how many calories to consume. RDs can help shape practical recommendations for individuals, such as replacing bagged processed snacks with more healthful options (eg, mixed tree nuts, fruits, and vegetables), swapping soda and juices with water (and moderate amounts of red wine for adults), and regularly consuming fresh fruits as the usual dessert, setting aside sweets, ice cream, and cakes for occasional treats. Special attention may be necessary to reduce significant snacking in between meals. Diet quality can be improved by substituting red or processed meats with seafood, legumes, and nuts.
To get clients started, the Mediterranean Diet Pyramid is a consumer-friendly resource available from Oldways (a nonprofit food think tank in Boston) created in partnership with the Harvard School of Public Health and the World Health Organization.16 Although the pyramid shape suggests the proportion of foods to eat, it doesn’t specify portion sizes or specific amounts. RDs can help develop menus for patients to determine how much food to eat at each meal, depending on age, activity level, and body size. Oldways also offers a four-week Mediterranean Diet Menu Plan. Motivating public interest and teaching cooking skills for the MedDiet are fundamental needs that can increase nutritional value and demonstrate that the eating pattern can taste good.
As the MedDiet is essentially a plant-based diet, the cultivation of locally produced fresh food can contribute to a sustainable food system, promote farming as a viable option, and stimulate financial growth within a community. In addition to enhancing nutrition and encouraging a healthful lifestyle, dietitians can review with clients the environmental benefits of the MedDiet. As a plant-based diet, it has a smaller water footprint and lower greenhouse gas emissions than diets that rely more on animal products. The MedDiet also has a high sociocultural food value where eating is important beyond the physiological need for energy. Food is prepared in moderate portion sizes, avoiding waste, and is linked to high cultural, social, and economic value.15
Thought for Food
Now more than ever, RDs can cite strong scientific research that demonstrates the merits of the MedDiet eating pattern. Slavin recommends a gentle balance for nutrition practice: “A great body of evidence points toward the overall health-promoting qualities of diet patterns that are rich in fruits, vegetables, whole grains, and lean proteins (and especially fish and plant-based proteins) while limited in saturated fat, sodium, and added sugars (and the highly processed foods that provide them). As the overall field of nutrition is shifting back to an emphasis on food patterns (as opposed to individual nutrients), the Mediterranean diet is a very tangible example of this eating pattern that also has a growing body of evidence to support its use in specific cases, and many people also agree is tasty.” Slavin adds, “It’s also important that we don’t lose sight that there are other ways to achieve that healthy eating pattern, but they don’t have a name to easily communicate.”
Katz agrees: “I recommend a basic theme of optimal eating—real food, mostly plants—with which the Mediterranean diet is compatible. It’s not the only specific way of eating I recommend, but it is salient among them, and has long been.”
Now in its ninth year of diet rankings, U.S. News & World Report is self-described as the global authority in ranking and consumer advice. Certainly, evidence-based research supports its esteem for the MedDiet.
— KC Wright, MS, RDN, LD, is a research dietitian at Dartmouth-Hitchcock Medical Center and maintains a nutrition communications practice. She advocates for good food and sustainable food systems at www.wildberrycommunications.com.
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14. US Department of Agriculture; Department of Health and Human Services. Process to develop the 2020-2025 Dietary Guidelines for Americans: topics and scientific questions to be examined by the 2020 Dietary Guidelines Advisory Committee. https://www.cnpp.usda.gov/sites/default/files/dietary_guidelines_for_americans/
RevisedTopicsAndQuestions-ListB.pdf. Accessed February 13, 2018.
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