What is the Mediterranean Diet?

The Mediterranean Diet describes a way of eating inspired by the traditional cuisine in European countries by the Mediterranean Sea, but primarily Greece, Spain, and Italy. While the eating habits of these countries differ, they typically feature primarily plant-based foods, olive oil, and moderate amounts of dairy, fish, poultry, and eggs.

This lifestyle promotes minimally-processed, whole foods as a way to improve overall health. The U.S. News and World Report ranked the Mediterranean Diet as the best overall meal plan for years due to its reported benefits for heart health and longevity.

Reported Benefits of the Mediterranean Diet

Proponents of the Mediterranean diet have reported multiple health benefits, such as:

  • Increased heart health
  • Reduced inflammation
  • Diabetes prevention
  • Achieving a healthy weight.

In this article, we will discuss the scientific findings behind each of these claims to determine if there is enough empirical evidence to suggest that the Mediterranean Diet provides these benefits. But first, what is the Mediterranean Diet?

Mediterranean Diet Food List

The Mediterranean Diet encourages a balanced diet with various nutritious food sources. You can eat meat or follow a wholly plant-based diet while still lying within the Mediterranean guidelines. It deters its followers from consuming sweets with added sugar, vegetable oils, trans fats, refined white grains, and processed foods.

What Foods Can I Eat?

Here are some foods you can enjoy on the Mediterranean Diet:

  • Leafy Greens: arugula, collard greens, kale, spinach
  • Vegetables: asparagus, broccoli, Brussels sprouts, carrots, cauliflower, onions, zucchini
  • Tubers: beets, parsnips, potatoes, sweet potatoes, yams
  • Fruits: apples, apricots, avocados, bananas, blueberries, cantaloupe, citruses, cucumbers, dates, figs, grapes, kiwi, mangoes, melons, olives, peaches, pears, strawberries, tomatoes
  • Whole Grains: barley, brown rice, buckwheat, corn, couscous, Ezekiel bread, farro, millet, sprouted grains, quinoa, whole-grain bread, whole-grain oats, whole-grain pasta
  • Legumes: beans, chickpeas, lentils, peanuts, peas, pulses
  • Nuts and Seeds: almonds, cashews, chia seeds, flax seeds, hazelnuts, macadamia nuts, pistachios, sunflower seeds, pumpkin seeds, walnuts
  • Seafood and Fish: anchovies, clams, crab, mackerel, mussels, oysters, salmon, sardines, shrimp, trout, tuna
  • Dairy and Eggs: cheese, chicken eggs, duck eggs, Greek yogurt, milk, and quail eggs, but preferably pasture-raised and unprocessed; also an emphasis on goat-derived dairy
  • Poultry: chicken, duck, goose, turkey
  • Healthy Fats: avocado oil, extra virgin olive oil
  • Beverages: water, coffee, red wine (optional), tea, unsweetened juices

The Mediterranean Diet recommends using as many leafy greens, tubers, vegetables, fruits, legumes, nuts, seeds, fish, seafood, and healthy fats as you would like in your cooking. They limit dairy, eggs, and poultry to a few times a week and red meat to special occasions.

What Foods Can’t I Eat?

On the Mediterranean Diet, you are to avoid eating:

  • Added Sugars: baked goods, candy, chocolate, cookies, ice cream, juice, energy drinks, pastries, soda, sports drinks, table sugar
  • Convenience Foods: chips, fast food, frozen or microwave dinners, popcorn, pretzels
  • Processed Meats: bacon, hot dogs, lunch meat, salami, sausage
  • Refined Grains: biscuits, crackers, flour tortillas, white bread, white pasta, white rice
  • Refined Oils: canola oil, corn oil, safflower oil, soybean oil, vegetable oil

The diet recommends eating fruit as a dessert and minimizing these food items as much as possible. While strict followers will eliminate them, you can still occasionally partake in a slice of cake or fried meal.

Studies On the Mediterranean Diet

Researchers have performed many studies to evaluate the benefits of the Mediterranean Diet. Here are four different studies on the effects of the diet.

1. Effect of a Mediterranean Diet Supplemented with Nuts on Metabolic Syndrome Status (Salvas-Savado, et al., 2008)

The investigators recruited 1,224 participants from the PREDIMED Study. This study was a  randomized trial determining the benefits of the Mediterranean Diet for cardiovascular disease prevention. Here, they used older subjects at risk of heart disease.

They gave the participants quarterly lessons about the diet and experimented with the fats involved. The researchers instructed a low-fat diet for the control group and 1 liter per week of extra virgin olive oil or 30 grams per day of mixed nuts as the predicting variables. They discouraged an increase in activity and assessed the relevant lifestyle variables with the National Cholesterol Education Program Adult Treatment Panel III criteria.

The researchers administered a 14-item questionnaire to determine the adherence to the diet, as well as other surveys to eliminate other variables like physical activity and food items. To encourage adherence, they gave the subjects free olive oil and mixed nuts, depending on their group. The control group received oil dispensers and low-fat recipe books to help. Each participant had a dietitian as well to instruct them on improving their diet.

Results

At the beginning of the study, 61.4% of the test subjects matched the criteria for metabolic syndrome, which is a group of conditions that increases the risk of heart disease. After one year, the research team found a 2.0%, 6.7%, and 13.7% decrease in these values for the control, olive oil, and mixed nuts groups, respectively.

Adjusting for age, obesity, weight changes, and sex, they found an odds ratio for the reversion of metabolic syndrome to be between 0.8 and 2.1 with a 95% confidence interval for the olive oil group and 1.1 to 2.6 for the nuts group compared to the control. Odds ratios measure the association between two events (e.g., eating nuts and reversing heart disease).

These findings suggested that a Mediterranean Diet with nuts can significantly decrease the prevalence of metabolic syndrome, which in turn decreases your risk of stroke, heart disease, and diabetes.

2. Adherence to the Mediterranean Diet and Inflammatory Markers (Sureda, et al., 2018)

The study conducted by Sureda and their team assessed how the inflammatory markers changed amongst adolescents and adults following the Mediterranean Diet. It involved a random sample of 598 residents of the Balearic Islands population between ages 12 and 65.

They took blood samples to find the inflammation biomarkers, including metabolic syndrome prevalence, leptin, plasminogen activator inhibitor 1 (PAI-1), tumor necrosis factor-alpha (TNF-ɑ), high-sensitivity C-reactive protein (hs-CRP), and adiponectin. Inflammatory markers are proteins in the blood whose concentrations change during inflammation.

The researchers assessed the dietary habits and adherence to the Mediterranean Diet, which improves the results from the first listed study.

Results

In adolescents, they found that 51.3% of males and 53.1% of females adhered to the Mediterranean diet. For adults, it was 45.7% and 44.3% for males and females, respectively.

In males, increased adherence correlated to several lower inflammatory markers, including leptin, PAI-1, TNF-ɑ, and hs-CRP and higher adiponectin. The investigators found these results in adults, but not adolescent, subjects. For females, greater adherence corresponded to lower leptin and hs-CRP for adolescents and lower PAI-1 and hs-CRP for adults.

Those advanced in age had a greater prevalence of metabolic syndrome, yet they did not adhere to the diet as much. Less adherence correlated to increased metabolic syndrome and a poor inflammation marker profile.

3. Reduction in the Incidence of Type 2 Diabetes with the Mediterranean Diet (Salas-Salvado, et al., 2011)

This study compared the effects of a Mediterranean Diet rich in free virgin olive oil or mixed nuts with a low-fat diet on the incidence of diabetes. The researchers used 418 non-diabetic test subjects between the ages of 55 and 80 recruited in the northeastern Spain PREDIMED study. These individuals had a high cardiovascular risk.

The team assigned the participants randomly to educate them on low-fat diets, and Mediterranean Diets supplemented with 1 liter per week of free virgin olive oil or 30 grams per day of mixed nuts.

In the courses, they did not provide a meal plan or advice on physical activity. They measured adherence with a 14-item questionnaire to give personalized dietary advice. The general instruction included using plenty of olive oil, eating more vegetables, fruits, fish, and legumes, reducing meat consumption, making their tomato sauce, avoiding processed and sugary foods, and drinking red wine.

The control group received gifts to encourage a low-fat diet, such as recipe books and oil dispensers. The team encouraged adherence, but they did not monitor the participants regularly. The study lasted several years, with the median follow-up being four years.

Results

After four years, the olive oil group had 10.1% diabetes incidence, the mixed nuts group had 11.0%, and the control group had 17.9%. The 95% confidence interval ranged from 5.1 to 15.1, 5.9-16.1, and 11.4-24.4 for olive oil, nuts, and control, respectively. A confidence interval is a range of values with a defined probability that the result lies within those boundaries.

Pooling those who adhered to the Mediterranean Diet showed that diabetes incidence had reduced by 52%. The confidence interval ranged from 27% to 86%.

For both groups, following the Mediterranean Diet lessened diabetes incidence in individuals at high cardiovascular risk. They did not restrict calories or alter their physical activity.

4. Systematic Review of the Mediterranean Diet for Long-Term Weight Loss (Mancini, et al., 2016)

In this study the researchers reviewed randomized controlled trials to see how the Mediterranean Diet impacted weight loss and heart health after 12 months. They reviewed the Cochrane Library of Clinical Trials, MEDLINE, and EMBASE for studies that had follow-ups over 12 months after the observation period ended to see if they had long-term weight loss and improved cardiovascular risk factor levels in overweight individuals.

They found five trials that met their criteria, with four trials comparing the Mediterranean Diet to a low-fat diet, two comparing it to a low-carbohydrate diet, and one to the American Diabetes Association diet.

Results

The researchers discovered that the Mediterranean Diet showed greater weight loss than a low-fat diet after 12 months. The Mediterranean Diet showed a loss of 4.1 to 10.1 kg, while the low-fat one displayed a gain of 2.9 kg to a loss of 5.0 kg.

However, the Mediterranean Diet performed similarly to the low-carbohydrate and American Diabetes Association Diet (losing 4.1 to 10.1 kg and 4.7 to 7.7 kg, respectively). Also, these diets improved lipid and blood pressure levels as well.

Overall, the Mediterranean Diet helped individuals lose weight, but not exceptionally well compared to other diets.

Conclusion

When comparing the results of the study to the reported health benefits, it seems that the Mediterranean Diet improves heart health by reducing cardiovascular risk factors. Also, it reduces inflammatory markers and diabetes incidence.

While the Mediterranean Diet can lead to weight loss, the individual must ensure they do not eat in a surplus of calories. Although healthy, high-fat foods are calorically dense, so the person may need to track the amount they consume when looking to lose weight.

Nonetheless, a Mediterranean Diet contributes to a healthier lifestyle. By combining a way of eating filled with fruits, vegetables, fish, legumes, whole grains, and healthy fats, one can improve their quality of life. These benefits are expanded through the inclusion of physical activity and maintaining a healthy weight.

References

Mancini, J. G., Filion, K. B., Atallah, R., & Eisenberg, M. J. (2016). Systematic Review of the

Mediterranean Diet for Long-Term Weight Loss. The American journal of medicine, 129(4), 407–415.e4. https://doi.org/10.1016/j.amjmed.2015.11.028

Salas-Salvadó, J., Fernández-Ballart, J., Ros, E., Martínez-González, M. A., Fitó, M., Estruch,

R., Corella, D., Fiol, M., Gómez-Gracia, E., Arós, F., Flores, G., Lapetra, J., Lamuela-Raventós, R., Ruiz-Gutiérrez, V., Bulló, M., Basora, J., & Covas, M. I. (2008). Effect of a Mediterranean diet supplemented with nuts on metabolic syndrome status: one-year results of the PREDIMED randomized trial. Archives of internal medicine, 168(22), 2449–2458. https://doi.org/10.1001/archinte.168.22.2449

Sureda, A., Bibiloni, M. d. M., Julibert, A., Bouzas, C., Argelich, E., Llompart, I., Pons, A., & Tur,

  1. A. (2018, January 10). Adherence to the Mediterranean diet and inflammatory markers. Nutrients, 10(1), 62. https://dx.doi.org/10.3390%2Fnu10010062

Salas-Salvadó, J., Bulló, M., Babio, N., Martínez-González, M. Á., Ibarrola-Jurado, N., Basora,

J., Estruch, R., Covas, M. I., Corella, D., Arós, F., Ruiz-Gutiérrez, & V., Ros, E. (2011). Reduction in the incidence of type 2 diabetes with the Mediterranean diet: results of the PREDIMED-Reus nutrition intervention randomized trial. Diabetes care, 34(1), 14–19. https://doi.org/10.2337/dc10-1288