The Mediterranean diet has stood the test of time. It is one of the healthiest diets that an individual can follow and leads to many positive health outcomes. It is easy to see why health care providers commonly refer their patients to this way of eating.  Most importantly, the benefits are evidence-based; the research is reviewed below. The Mediterranean diet refers to a diet high in healthy fats and low in processed foods. It is common amongst those living in Crete, much of the rest of Greece, and southern Italy. In these regions, life expectancy is among the highest in the world and rates of coronary heart disease, certain cancers, and other chronic diseases are among the lowest. The people in these regions are also more physically active and typically eat meals in larger groups with social support which may also influence the benefits of this diet (Willet-Trichopoulos, 1995). The Mediterranean diet is low in saturated fats (≤ 7-8% of energy), however the total fat ranges from less than 25% to greater than 35% of energy.

Typical Food Choices          

• Whole, unprocessed plant food (vegetables, fruits, potatoes, beans, and seeds)
• Nuts
  • Almonds, which are high in vitamin e and magnesium
  • Peanuts, which are high in protein and folate
  • Brazil nuts, which are high in selenium
  • Cashews, which are high in magnesium
  • Walnuts, which are high in alpha-linoleic acid (an omega-3 fatty acid)
• Unprocessed whole grain bread or sourdough bread
• Olive oil as the principal source of fat
• Moderate intake of fish and poultry
• Zero to four eggs each weekly
• Low intake of dairy products, red meat, processed meats, and sweets
• Wine in moderation, consumed with meals

Foods to Avoid

• Sugar, such as that added to drinks, or found in candy, cookies, and bakery goods
• Processed foods

What Does the Evidence Reveal?

Reduced risk of cancers and chronic diseases with adherence to a Mediterranean diet

• In a meta-analysis of randomized trials, adherence to a Mediterranean diet was associated with primary prevention of major chronic diseases, leading to a reduction in mortality (9%), incidence of or mortality from cancer (6%), and incidence of Parkinson’s disease or Alzheimer’s disease (13%) (Sofi, Abbate, Gensini, and Casini, 2008).
• In a meta-analysis of cohort or case-controlled studies, the highest adherence to a Mediterranean diet resulted in a significant risk reduction for overall cancer mortality, and incidence for colorectal, prostate, and aerodigestive cancer (Schwingshacki and Hoffman, 2014).

Mediterranean diet may help prevent type 2 diabetes

• At least five large prospective studies report a substantially lower risk of type 2 diabetes in healthy people or at-risk patients with the highest adherence to a Mediterranean diet (Esposito and Gugliano, 2014).

• Five randomized controlled trials have evaluated the effects of a Mediterranean diet, as compared with other commonly used diets, on glycemic control in subjects with type 2 diabetes. Improvement of HbA1c levels was greater with a Mediterranean diet and ranged from 0.1% to 0.6% for HbA1c. No trial reported worsening of glycemic control with a Mediterranean diet (Esposito and Gugliano, 2014).

Reduced risk of cardiovascular disease and stroke with adherence to a Mediterranean diet

• In a cohort study of 25,994 women in the United States, adherence to a Mediterranean diet was associated with a one-fourth relative risk reduction in cardiovascular disease which was explained by reductions in inflammation, insulin resistance, body mass index, blood pressure and lipids (Ahmad-Mora, 2018).
• In an observational prospective population-based study cohort study of 23,232 men and women aged 40 to 77 years old in the United Kingdom, the risk of stroke was significantly reduced with greater adherence to the Mediterranean diet (Paterson-Welch, 2018).
• In a systematic review of experimental studies, the Mediterranean diet showed favorable effects on lipoprotein levels, endothelium vasodilatation, insulin resistance, metabolic syndrome, antioxidant capacity, myocardial and cardiovascular mortality, and cancer incidence in obese patients and in those with previous myocardial infarction (Serra-Majem, Roman, and Estruch, 2006).
• The Lyon Diet Heart Study was a randomized secondary prevention trial that looked at the rate of cardiovascular complications after myocardial infarction and demonstrated that the protective effect of the Mediterranean diet was maintained up to 4 years after the first infarction (de Lorgeril- Mamelle, 1999).

Adherence to a Mediterranean diet corresponded to weight loss at equal rates of other diets, especially if frequent monitoring was used

• In a randomized controlled study in Greece, the intervention group attended a 20-minute personalized session on the Mediterranean diet and the diet was adjusted every 2 weeks, while the control group was provided a handout on healthy nutrition and Mediterranean diet. Subjects in the intervention group had decreased weight, waist circumference, and body fat percentage at the end of the study, while in the control group, weight and waist circumference increased (Hassapidou- Tzotzas, 2019).
• In a systematic review of the Mediterranean Diet for long-term weight loss, the findings suggested that the Mediterranean diet resulted in greater weight loss than the low-fat diet, but produced similar weight loss as the low-carbohydrate diet and the American Diabetes Association diet (Mancini, Filion, Atallah, and Eisenberg, 2016).
• A meta-analysis of randomized controlled trials concluded that a Mediterranean diet may be a useful tool to reduce body weight, especially when the Mediterranean diet is energy-restricted, associated with physical activity, and more than 6 months in length (Esposito, Kastorini, Panagiotakos and Giugliano, 2011). 

In conclusion…

The benefits of a Mediterranean diet are derived from the positive nutritious components of the fruits, vegetables, legumes and nuts which have the necessary complement of vitamins and minerals without the added calories of processed foods. It is also believed that the nuts and oleic acid from the olive oil have their own protective qualities. Other positive factors that play a role are the lifestyle of the individuals who adhere to this diet and the social environment in which they live. Studies conclude that the benefits of the diet are only as good as the adherence to it, and that adherence tends to be higher when behavioral mechanisms are in place.  

References:
Ahmad, S., Moorthy, M., Demler, O., Hu, F., Ridker, P., Chasman, D., Mora, S., (2018). Assessment of Risk Factors and Biomarkers Associated with Risk of Cardiovascular Disease Among Women Consuming a Mediterranean Diet. Journal of the American Medical Association, 1 (8). doi:10.1001/jamanetworkopen.2018.5708
 
de Lorgeril, M., Salen, P., Martin, J., Monjaud, I., Delaye, J., Mamelle, N., (1999). Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation, 99 (779-785).
 
Esposito, K., Kastorini, C., Panagiotakos, D., Giugliano, D. (2010). Mediterranean diet and weight loss: meta-analysis of randomized controlled trials. Metabolic Syndrome and Related Disorders, 9 (1) 1-12. doi: 10.1089/met.2010.0031.
 
Hassapidou, M., Tziomalos, K., Lazaridou, S., Pagkalos, I., Papadimitriou, K., Kokkinopoulou, A., Tzotzas, T., (2019). The Nutrition Health Allianc (NutiHeAl) Study: A Randomized Controlled Nutritional Intervention Based on Mediterranean Diet in Greek Municipalities. Journal of the American College of Nutrition, (1-7). E-publication ahead of print, doi: 10.1080/07315724.2019.1660928.
 
Mancini, J., Filion, K., Atallah, R. Eisenber, M. (2016). Systematic Review of the Mediterranean Diet for Long-Term Weight Loss. American Journal of Medicine, 129 (4) 407-415.e4. doi: 10.1016/j.amjmed.2015.11.028

Paterson, K., Myint, P., Jennings, A., Bain, L., Lentjes, M., Khaw, K., Welch, A., (2018). Mediterranean Diet Reduces Risk of Incident Stroke in a Population with Varying Cardiovascular Disease Risk Profiles. Journal of the American Medical Association, 1(8) doi: e185708.

Schwingshackl, L., Hoffmann, G., (2014). Adherence to Mediterranean diet and risk of cancer: a systematic review and meta-analysis of observational studies. International Journal of Cancer, 135 (1884-1897). doi.org/10.1002/ijc.28824  

Serra-Majem, L., Roman, B., Estruch, R., (2006). Scientific evidence of interventions using the Mediterranean diet: a systematic review. Nutrition Reviews 64(2 Pt 2):S27-47. doi: 10.111/j.1753-4887.2006.tb00232.x 

Sofi, F., Abbate, R., Gensini, G., Casini, A. (2010). Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. American Journal of Clinical Nutrition, 92 (1189-1196).

Willet, W.C., Sacks, F., Trichipoulou, A., Drescher, G., Ferro-Luzzi, A., Helsing, E., Trichopoulos, D. (1995). Mediterranean diet pyramid: a cultural model for healthy eating. American Journal of Clinical Nutrition, 61 (Suppl:1402S-1406S).