The enduring popularity of the Mediterranean diet is attributable to three things:
3. Health benefits
For our purposes today, I use “diet” to refer to the usual food and drink of a person, not a weight-loss program.
The scientist most responsible for the popularity of the diet, Ancel Keys, thought the heart-healthy aspects of the diet related to low saturated fat consumption. He also thought the lower blood cholesterol levels in Mediterranean populations (at least Italy and Greece) had something to do with it, too. Dietary saturated fat does tend to raise cholesterol levels.
Even if Keys was wrong about saturated fat and cholesterol levels being positively associated with heart disease, numerous studies (involving eight countries on three continents) strongly suggest that the Mediterranean diet is one of the healthiest around. See References below for the most recent studies.
Relatively strong evidence supports the Mediterranean diet’s association with:
■ increased lifespan
■ lower rates of cardiovascular disease such as heart attacks and strokes
■ lower rates of cancer (prostate, breast, uterus, colon)
■ lower rates of dementia
■ lower incidence of type 2 diabetes
Weaker supporting evidence links the Mediterranean diet with:
■ slowed progression of dementia
■ prevention of cutaneous melanoma
■ lower severity of type 2 diabetes, as judged by diabetic drug usage and fasting blood sugars
■ less risk of developing obesity
■ better blood pressure control in the elderly
■ improved weight loss and weight control in type 2 diabetics
■ improved control of asthma
■ reduced risk of developing diabetes after a heart attack
■ reduced risk of mild cognitive impairment
■ prolonged life of Alzheimer disease patients
■ lower rates and severity of chronic obstructive pulmonary disease
■ lower risk of gastric (stomach) cancer
■ less risk of macular degeneration
■ less Parkinsons disease
■ increased chance of pregnancy in women undergoing fertility treatment
■ reduced prevalence of metabolic syndrome (when supplemented with nuts)
■ lower incidence of asthma and allergy-like symptoms in children of women who followed the Mediterranean diet while pregnant
Did you notice that I used the word “association” in relating the Mediterranean diet to health outcomes? Association, of course, is not causation.
The way to prove that a particular diet is healthier is to take 20,000 similar young adults, randomize the individuals in an interventional study to eat one of two test diets for the next 60 years, monitoring them for the development of various diseases and death. Make sure they stay on the assigned test diet. Then you’d have an answer for that population and those two diets. Then you have to compare the winning diet to yet other diets. And a study done in Caucasians would not necessarily apply to Asians, Native Americans, Blacks, or Hispanics.
Now you begin to see why scientists tend to rely on observational rather than interventional diet studies.
I became quite interested in nutrition around the turn of the century as my patients asked me for dietary advice to help them lose weight and control or prevent various diseases. At that time, the Atkins diet, Mediterranean diet, and Dr. Dean Ornish’s vegetarian program for heart patients were all prevalent. And you couldn’t pick three programs with more differences! So I had my work cut out for me.
After much scientific literature review, I find the Mediterranean diet to be the healthiest for the general population. People with particular medical problems or ethnicities may do better on another diet. People with diabetes or prediabetes are probably better off with a carbohydrate-restricted diet, such as the Low-Carb Mediterranean Diet.
Dan Buettner makes a good argument for plant-based diets in his longevity book, The Blue Zones. The Mediterranean diet qualifies as plant-based.
What do you consider the overall healthiest diet, and why?
References (updated September 6, 2010):
Sofi, Francesco, et al. Accruing evidence about benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. American Journal of Clinical Nutrition, ePub ahead of print, September 1, 2010. doi: 10.3945/ajcn.2010.29673
Buckland, Genevieve, et al. Adherence to a Mediterranean diet and risk of gastric adenocarcinoma within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort study. American Journal of Clinical Nutrition, December 9, 2009, epub ahead of print. doi: 10.3945/ajcn.2009.28209
Feart, Catherine, et al. Adherence to a Mediterranean diet, cognitive decline, and risk of dementia. Journal of the American Medical Association, 302 (2009): 638-648.
Scarmeas, Nikolaos, et al. Physical activity, diet, and risk of Alzheimer Disease. Journal of the American Medical Association, 302 (2009): 627-637.
Scarmeas, Nikolaos, et al. Mediterranean Diet and Mild Cognitive Impairment. Archives of Neurology, 66 (2009): 216-225.
Fung, Teresa, et al. Mediterranean diet and incidence of and mortality from coronary heart disease and stroke in women. Circulation, 119 (2009): 1,093-1,100.
Mente, Andrew, et al. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease. Archives of Internal Medicine, 169 (2009): 659-669.
Salas-Salvado, Jordi, et al. 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 (2008): 2,449-2,458.
Mozaffarian, Dariush, et al. Incidence of new-onset diabetes and impaired fasting glucose in patients with recent myocardial infarction and the effect of clinical and lifestyle risk factors. Lancet, 370 (2007) 667-675.
Esposito, Katherine, et al. Effects of a Mediterranean-style diet on the need for antihyperglycemic drug therapy in patients with newly diagnosed type 2 diabetes. Annals of Internal Medicine, 151 (2009): 306-314.
Martinez-Gonzalez, M.A., et al. Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study. British Medical Journal, BMJ,doi:10.1136/bmj.39561.501007.BE (published online May 29, 2008).
Trichopoulou, Antonia, et al. Anatomy of health effects of the Mediterranean diet: Greek EPIC prospective cohort study. British Medical Journal, 338 (2009): b2337. DOI: 10.1136/bmj.b2337.