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Unravelling the Mediterranean diet: where does its dietary fame come from?

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Posted July 21, 2014

The health benefits of the Mediterranean diet have been featuring within the news media for years now. But what is in it really that, as the headlines claim, determines a healthy heart and boosts your longevity? As more research emerges, can we single out certain foods and nutrients that contribute the lion’s share to our health?

Credit: Carlos Lorenzo via Flickr (CC BY-NC-ND 2.0)

Credit: Carlos Lorenzo via Flickr (CC BY-NC-ND 2.0)

A recent trial-based PREDIMED (Prevención con Dieta Mediterránea) study, involving over 7,000 men and women from Spain with high cardiovascular disease risk, has concluded that typical Mediterranean foods, such as olive oil and nuts, are key to keeping your heart healthy, and a diet enriched in valuable vegetable oils trumps that of a low-fat angle. On the other hand, little was considered about the effects of individual nutrients or the importance of the background diet.

Several subsequent studies, however, have taken the PREDIMED findings a little further. Accordingly, certain foods and nutrients were identified or re-confirmed as the ultimate “leads” within the diet traditional in Greece, Italy and Spain, which is by itself some of most popular nutritional recommendations in the modern world.

Polyphenols – key “Mediterranean” nutrients

Nutrients are key biological molecules that deliver nutritional values to individual foods and specific diets. Plant-based foods, found in abundance within the Mediterranean diet, are particularly rich in polyphenols, famous for their antioxidant properties. In fact, a number of epidemiological studies have identified polyphenols as major players in reducing the risk of cancers, cardiovascular diseases, diabetes, osteoporosis and neurodegenerative disorders.

A recent “re-analysis” of the PREDIMED study, published in BMC Medicine, has found a whopping 37% relative risk reduction for overall mortality between people with highest and lowest polyphenol intakes. However, not all polyphenols were found to be equal in this matter – in fact, study participants who consumed the highest amounts of stilbenes and lignans experienced the greatest mortality risk reduction, while other polyphenol groups did not seem stand out from other nutrients. This is consistent with previous studies reporting an inverse association between olive oil and red wine consumption and mortality risk.

These findings added to another PREDIMED analysis recently published in Nutrition, Metabolism and Cardiovascular Diseases, which has discovered a 46% cardiovascular disease risk reduction in those having the highest amounts of polyphenols in their diets. Some curious findings were uncovered by a few other investigations as well, such as one claiming a stronger effect of polyphenols in women who abstain from alcohol, and another suggesting those starting with the worst dietary habits benefit the most from these nutrients, after they make a change for the better.

Plant foods central to the Mediterranean diet are rich in polyphenols –nuts, olive oil, fruits and vegetables, coffee, chocolate and even red wine all contain significant amounts of these nutrients. However, olives and olive oil seem to be the ultimate frontrunners amongst polyphenol-rich foods.

Mediterranean diet pyramid. Image from https://www.diabetesaction.org

Mediterranean diet pyramid. Image from diabetesaction.org

Olive oil, especially extra-virgin, is central to maintaining cardiovascular health

Another PREDIMED-based study in BMC Medicine has recently confirmed the direct effects of olive oil and olives in keeping your heart healthy. Participants with the highest intake of common and extra-virgin olive oil were found to be 35% and 39% less likely to succumb to cardiovascular disease, respectively. Moreover, each 10 g a day increase in extra-virgin olive oil intake was shown to contribute to a 10% lower likelihood of experiencing a cardiovascular event and a 7% lower risk of cardiovascular death.

Olive oil is a particularly good source of polyphenols, but processing is known to reduce its nutrition value greatly. In fact, besides an abundance of polyphenols, virgin olive oil, produced directly from mechanically pressed olives, contains various bioactive and antioxidant compounds, such as phytosterols and vitamin E. Extra-virgin is even better in this case, since it is the oil of the best quality. Regular, or so called common olive oil, on the other hand, consists mainly of refined oil that has been processed leading to greatly reduced antioxidant and anti-inflammatory content.

Instead, extra-virgin olive oil, especially while adhering to the whole Mediterranean diet, has been related to an improved lipid metabolism, insulin sensitivity, better control of blood pressure and blood sugar content, and inversely associated with type 2 diabetes – all of which are considered significant risk factors for cardiovascular death.

Major cardiovascular events were also found to be 25% less likely to occur in participants consuming the highest amounts of olive fruits themselves, adding to the notable reputation of the Mediterranean kitchen.

Sticking to good dietary habits remains above all

Identifying individual nutrients might help you make better nutritional choices, but research shows that maintaining a good background diet is crucial. In fact, the PREDIMED “re-analysis” has demonstrated that participants who adhere more strictly to the traditional Mediterranean diet, as well as those who are more physically active and less hypertensive tend to have naturally higher daily polyphenol intake.

Moreover, as some researchers suggest, the success of the PREDIMED study may be partially representative of the strict dietary counselling received by the participants. The trial included thorough dietary advice, as well as intervention, therefore, different results might have been achieved if the background diet was more variable. That is to say, olive oil will almost certainly not compensate the negative effects of an otherwise unhealthy diet, such as one enriched in “bad fats” and other heart-unhealthy foods.

On the other hand, all current evidence points to the traditional Mediterranean cuisine, possibly with some extra extra-virgin olive oil added here and there.

Written by Egle Marija Ramanauskaite

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