Is There Really a Mediterranean Diet? A Pattern, a Study and a Brand
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
A way of eating identified in the 1950s became the most studied dietary pattern in the world and then a marketing term. Separating what the research supports from what the label sells takes some care.
Where the idea came from
The concept originates in work by Ancel Keys and colleagues from the 1950s, comparing diet and heart disease across populations in seven countries, which found notably low rates of coronary disease in Crete and southern Italy alongside a diet high in olive oil, vegetables, legumes and bread and low in meat and dairy. The observation was genuine and the study had real limitations, including the selection of the countries compared and the reliance on dietary surveys of small samples at a single period, and it has been criticised on both grounds for decades. The pattern described was also a pattern of relative poverty in a rural population, which is part of why meat was scarce, and that context is frequently omitted.
What the pattern contains
The dietary pattern as defined in research has consistent components:
- •Olive oil as the principal fat, in substantial quantity
- •Vegetables, fruit, legumes, nuts and whole grains in quantity and daily
- •Fish and seafood regularly, and poultry, eggs and dairy in moderation
- •Red meat and processed meat rarely
- •Wine in moderation with meals, which is included in most definitions and is the most contested element
- •Very little in the way of refined sugar and processed food
What the evidence shows
The pattern is among the best supported in nutrition, which is a lower bar than it sounds given the difficulty of the field. Large observational studies consistently associate closer adherence with lower cardiovascular disease and lower mortality, across many populations including well outside the Mediterranean. One large randomised trial in Spain reported a substantial reduction in cardiovascular events among participants assigned to the pattern supplemented with olive oil or nuts, which is unusual because randomised dietary trials at that scale are rare, and that trial was retracted and republished in 2018 after irregularities in how some participants were randomised, with the reanalysis reporting a smaller but still positive result. The honest summary is that the evidence is good by nutritional standards and is not the settled matter that popular coverage suggests.
Why single foods explain little
Attempts to identify which component does the work have largely failed, and the failure is informative about nutrition generally. Olive oil, fish, nuts, wine and specific compounds have each been tested in isolation with results that are weaker and less consistent than those for the whole pattern. Several plausible explanations exist. Components may interact, so that fat from olive oil helps absorb compounds from vegetables eaten with it. What the pattern excludes may matter as much as what it contains, since eating this way displaces other things. The pattern is bound up with meal structure, physical activity and social eating, which trials cannot isolate. And a dietary pattern may simply be the right unit of analysis, which is the direction nutritional research has moved over the past two decades.
What the label sells
The commercial afterlife of the concept has drifted well away from the research. Products are marketed with the term on the basis of containing olive oil or a Mediterranean-sounding ingredient, which has no relationship to the dietary pattern studied. Restaurant menus described that way frequently feature the meat, cheese and refined grain the pattern minimises. The version eaten in the countries concerned has itself changed enormously since the 1950s, with consumption of meat, dairy and processed food rising sharply and measured adherence falling, particularly among the young. The recognition of the pattern as cultural heritage in 2010 was sought partly to counter that trend. Anyone wanting the benefit the research describes has to eat the pattern rather than buy the label.
The takeaway
The idea comes from 1950s comparisons that found low heart disease alongside a diet heavy in olive oil, vegetables and legumes, in a rural population where meat was scarce partly through poverty. Observational evidence consistently associates adherence with lower mortality, and the major randomised trial was retracted and republished with a smaller positive result. The marketing term has drifted far from the pattern studied.