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How is the Mediterranean Diet Beneficial?

 

med dietThe Mediterranean diet that is now advocated by health professionals and dietitians for good health has been adapted from eating patterns once common in Southern Greece and Southern Italy in the early 1960s.1  At this time, diet-related diseases such as atherosclerosis and certain cancers and chronic diseases that were affected by diet were among the lowest in the world, and the adult life expectancy among the highest.1 Importantly, this diet was typically combined with a lifestyle favourable to cardiovascular and general health. Employment in this era commonly involved regular physical exercise in the open air and few individuals were significantly overweight.

The Mediterranean diet of the 1960s included mainly fruit, vegetables, grains, seeds, nuts, cereals and legumes. Fish and poultry were eaten in preference to beef, lamb and pork and eggs were eaten every second day or so on average. Wine was the main source of alcohol and was drunk in moderation with the meal.

Olive oil was used extensively in cooking and fats derived from animal products (cheese, milk, meat) were used in moderation; fat intake itself was not specifically restricted.1 The ratio of monosaturated fats (olive oil, nuts, fatty fish) to saturated fats was approximately 2:1.2  In particular, the intake of saturated fat was generally low, calculated in one study as less than or equal to 7-8% of the daily energy intake, with total fat ranging from less than 25% to greater than 35% of energy intake throughout the region.1

“Compared with a low-fat diet, patients randomised to a Mediterranean diet had a 30% reduced risk of a cardiovascular event at 5 years.

The Mediterranean diet may also be indicated to:

Research into the Mediterranean diet concludes a biological plausibility for the reduction in cardiovascular disease in high risk, asymptomatic people.3 The results have been attributed to a number of factors, such as the effect of weight loss (and consequent reduction in diabetes and the metabolic syndrome), altered oxidation, inflammation, and endothelial function (mainly attributed to beneficial effects of fresh fruit and vegetables, nuts, extra-virgin olive oil and fish). Extra-virgin olive oil intake, in particular, appears to have an inverse relation to acute cerebrovascular incidents.It is also plausible that the consumption of wine with the meal contributes to a lower overall glycaemic profile, given that alcohol causes hypoglycaemia.

It is clear from the Women’s Health Initiative Dietary Modification Trial that a diet low in fat alone does not lower cardiovascular risk, especially compared to the Mediterranean diet.3

It is also likely that the ratio of omega-6 polyunsaturated fatty acids to omega-3 polyunsaturated fatty acids in the Western versus Mediterranean diet may have something to do with the altered risk patterns for certain diseases researched. Western diets currently have a very high omega-6 to omega-3 ratio (i.e. tend to be relatively omega-3 deficient).4

However, nuts tend to be higher in omega-6, fatty fish higher in omega-3 and extra-virgin olive oil higher in omega-6.

“In the secondary prevention of cardiovascular disease, a ratio of 4/1 was associated with a 70% decrease in total mortality. A ratio of 2.5/1 reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4/1 with the same amount of omega-3 PUFA had no effect. The lower omega-6/omega-3 ratio in women with breast cancer was associated with decreased risk. A ratio of 2-3/1 suppressed inflammation in patients with rheumatoid arthritis, and a ratio of 5/1 had a beneficial effect on patients with asthma, whereas a ratio of 10/1 had adverse consequences. “4

In summary, it appears that a Mediterranean diet reduces cardiovascular risk and cerebrovascular accidents in high risk individuals. It also independently lowers the risk and severity of type 2 diabetes, and colorectal and breast cancers especially.  The currently researched foods associated with these findings appear to be, in particular, extra-virgin olive oil, nuts and fatty fish. This may be due to the omega-6 to omega-3 polyunsaturated fatty acid ratios in the Mediterranean diet.

 

1. Willett W. C., Sacks, F. et al. Mediterranean diet pyramid: a cultural model for healthy eating The American Journal of Clinical Nutrition, June 1995, 61(6 Suppl):1402S-1406S
http://ajcn.nutrition.org/content/61/6/1402S.abstract

2. RACGP, Mediterranean diet: reducing cardiovascular disease risk, May 2014
http://www.racgp.org.au/your-practice/guidelines/handi/interventions/nutrition/the-mediterranean-diet-for-reducing-cardiovascular-disease-risk/

3. Estruch, R. et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. The New England Journal of Medicine, 4 April 2013, 368:1279-1290
http://www.nejm.org/doi/full/10.1056/NEJMoa1200303#t=articleTop

4. Simopoulos A. P1The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomedicine Pharmacotherapy, 2002 Oct; 56(8):365-79.
http://www.ncbi.nlm.nih.gov/pubmed/12442909