What is a Mediterranean Style Diet?

The recently released 2018 Clinical Practice Guidelines (CPG) Guidelines of Diabetes Canada recommend that those with Diabetes continue to eat 45% to 65% of their daily calories as carbohydrate, 10% to 35% of their daily calories as protein and only 20% to 35% of their daily calories, yet affirm that there is “evidence to support a number of other macronutrient-, food- and dietary pattern-based approaches” and that “evidence is limited for the rigid adherence to any single dietary approach”[1] .

One of the dietary patterns they recommend is a “Mediterranean-style dietary pattern” in order to “reduce major cardiovascular events and improve glycemic (blood sugar) control.”

So what is a “Mediterranean-style dietary pattern“?

According to the Clinical Practice Guidelines,

A “Mediterranean diet” primarily refers to a plant-based diet first described in the 1960s. General features include a high consumption of fruits, vegetables, legumes, nuts, seeds, cereals and whole grains; moderate-to-high consumption of olive oil (as the principal source of fat); low to moderate consumption of dairy products, fish and poultry; and low consumption of red meat, as well as low to moderate consumption of wine, mainly during meals”

Countries with coastlines on the Mediterranean Sea include Albania, Algeria, Bosnia and Herzegovina, Croatia, Cyprus, Egypt, France, Greece, Israel, Italy, Lebanon, Libya, Malta, Morocco, Monaco, Montenegro, Slovenia, Spain, Syria, Tunisia and Turkey and the diets of these countries vary considerably, so there isn’t only ONE “Mediterranean Diet“.

What is the Mediterranean Diet that the Clinical Practice Guidelines are referring to?

It would seem that they are referring to dietary intake based of southern Italy from the 1960s from when rates of chronic disease were reported to be amongst the lowest in the world and adult life expectancy was reported to be amongst the highest. That is, the health benefits of “The Mediterranean Diet” came out of Ancel Keys’ Six Country Study (1953) and later his Seven Countries Study (1970).  More on that below.

One of the academic papers that the Guidelines cites as the basis for a “Mediterranean diet” makes the direct link to Ancel Keys clear;

“Ecologic evidence suggesting beneficial health effects of the Mediterranean diet has emerged from the classic studies of
Keys.” [2]

In 1953, Ancel Keys published the results of his “Six Countries Study“[3], where it is said he demonstrated that there was an association between dietary fat as a percentage of daily calories and death from degenerative heart disease.

Four years later, in 1957, Yerushalamy published a paper with data from 22 countries [4], which showed a much weaker relationship between dietary fat and death by coronary heart disease than was suggested by Keys’s six country data (see below).

from [3].Keys, A. Atherosclerosis: a problem in newer public health. J. Mt. Sinai Hosp. N. Y.20, 118–139 (1953).

from [4] Yerushalmy J, Hilleboe HE. Fat in the diet and mortality from heart disease. A methodologic note. NY State J Med 1957;57:2343–54

Nevertheless, in 1970, Keys went on to publish his Seven Countries Study in which he maintained that there was an associative relationship between increased dietary saturated fat and Coronary Heart Disease – ignoring the data presented in Yerushalamy’s 1957 study and failing to study countries such as France, in which the relationship did not hold.

In Keys’ paper published in 1989 [5] which was based on food consumption patterns in the 1960s in the seven countries, he found that the average consumption of animal foods (with the exception of fish) was positively associated with 25 year Coronary Heart Disease deaths rates and the average intake of saturated fat was strongly related to 10 and 25 year CHD mortality rates. Keys published this study 32 years after Yerushalamy’s 1957 paper which showed a significantly weaker relationship, yet it seems that people only remember Key’s data.

Countries with coastlines on the Mediterranean Sea on which there was known dietary and disease data in 1957 and that Keys later ignored in 1970 included France (labelled #8 on Yerushalamy’s graph above) and Israel (labelled #11). France is known for the “French paradox” (a term which came about in the 1980s) because of their relatively low incidence of coronary heart disease (CHD) while having a diet relatively rich in saturated fats. According to a 2004 paper about the French Paradox, there was diet and disease data available from the French population that was carried out in 1986–87 and which demonstrated that the saturated fat intake of the French was 15% of the total energy intake, yet such a high consumption of saturated fatty acids was not associated with high Coronary Heart Disease incidence in France [6]. Nevertheless, Keys published his 1989 study [5] ignoring the French dietary and disease data that was available from 1986-1987 [6]. Was it because it didn’t fit his hypothesis?

The diet of the French in the 1960's was every bit a "Mediterranean Diet" as that of southern Italy, but since Ancel Keys ignored (or did not study) the French data in the 1960s, that "Mediterranean Diet" remains ignored in the guidelines of today.

According to the French Paradox paper, high saturated fat intakes combined with low Coronary Heart Disease rates were also observed in other Mediterranean countries, including Spain and that rates in other non-Mediterranean Europeans countries such as Germany, Belgium are similar [6].

Perhaps then, a ‘true’ Mediterranean Diet which is protective of Coronary Heart Disease ought not to be defined as being largely “plant-based” and “low in consumption of red meat and dairy” – which the French diet clearly is not, but rather should focus on being a diet high in consumption of specific types of vegetables and fruit, nuts and seeds, abundant in the use of olive oil and that includes regular consumption of wine with meals.

As outlined in a recent article, eight recent meta-analysis and systemic reviews which reviewed evidence from randomized control trials that had been conducted between 2009-2017 did not find an association between saturated fat intake and the risk of heart disease. As well, recently published results from the Prospective Urban and Rural Epidemiological (PURE) Study, the largest and most global epidemiological study carried out to date and published in the Lancet in December 2017 found that those who ate the largest amount of saturated fats had significantly reduced rates of mortality (death) and that low consumption of saturated fat (6-7% of calories) was actually associated with increased risk of stroke.

Also as described in a recent article, a study published at the end of March 2017 in Nutrients and which examined health and nutrition data from 158 countries worldwide found that total fat and animal fat consumption were least associated with the risk of cardiovascular disease, and that high carbohydrate consumption, particularly as cereals and wheat was most associated with the risk of cardiovascular disease – with both of these relationships holding up regardless of a nation’s average national income.

Final Thoughts…

The 2018 Clinical Practice Guidelines continue to recommend the health benefits of a “Mediterranean style diet” defined based on the 60-year-old-data of Ancel Keys’ Six Countries Study / 50 year old Seven Countries Study- when we now know that Keys excluded data that was available from countries including France, which did not fit his hypothesis.

Given that there seems to be increasing evidence that Keys’ Diet-Heart Hypothesis (the belief that dietary saturated fat causes heart disease) has been significantly challenged by newer data, is it not time to study the factors in the diet of this region that ARE protective against cardiovascular disease, and to redefine a Mediterranean diet in these terms?

Would you like to have a Meal Plan that emphasizes the foods of this region, including meat and cheese, fish and seafood, vegetables and fruit, nuts and seeds, olive oil and wine and which may play a protective role in heart heath?

Please send me a note using the Contact Me form located on the tab above, and I will reply as soon as possible.

To our good health!

Joy

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References

  1. Sievenpiper JL, Chan CB, Dwortatzek PD, Freeze C et al, Nutrition Therapy – 2018 Clinical Practice Guidelines, Canadian Journal of Diabetes 42 (2018) S64–S79 http://guidelines.diabetes.ca/docs/CPG-2018-full-EN.pdf
  2. Trichopoulou A, Costacou T, Bamia C et al, Adherence to a Mediterranean Diet and Survival in a Greek Population, N Engl J Med 2003;348:2599-608.
  3. Keys, A. Atherosclerosis: a problem in newer public health. J. Mt. Sinai Hosp. N. Y.20, 118–139 (1953).
  4. Yerushalmy J, Hilleboe HE. Fat in the diet and mortality from heart disease. A methodologic note. NY State J Med 1957;57:2343–54
  5. Kromhout D, Keys A, Aravanis C, Buzina R et al, Food consumption patterns in the 1960s in seven countries. Am J Clin Nutr. 1989 May; 49(5):889-94.
  6. Ferrières J. The French paradox: lessons for other countries. Heart. 2004;90(1):107-111.

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Author: Joy Kiddie, MSc, RD

Joy Y Kiddie MSc., RD - I'm a Registered Dietitian in private practice in British Columbia, Canada that provides low carb and ketogenic services in-person in my Coquitlam office, as well as by Distance Consultation (using Skype / telephone).