Polyphenols – The Star of the Mediterranean Diet
The Mediterranean Diet (or Mediterranean Diet Pattern) is a way of eating, based on the cultural eating habits of those living near the Mediterranean Sea.
After observing that there was less cardiovascular disease in areas of the world less economically well-off than the United States, scientists went on to evaluate the dietary habits of various geographical areas to determine the beneficial factors. This was known as the “seven countries study”. The Mediterranean Diet has subsequently emerged as one that has very objective and measurable health outcomes in humans.
The Mediterranean Diet consists mainly of:
- Fresh fruits and vegetables
- Whole grains
- Olive oil
- Saturated fats.
The Power of Polyphenols
While it has been determined that it is the combination and synergistic effect of the entire diet that provides health benefits, the main component of the foods in the Mediterranean Diet that provide these benefits are considered to be the polyphenols.
Polyphenols are a group of compounds that give plants their color. They are naturally endogenously produced by plants to protect them from injury and threats. When humans consume these vegetables, the benefits appear to be passed on.
There are actually 4 classes of polyphenols: phenolic acids, stilbenes, lignans (some are known as phytoestrogens) and, likely the most well-known, flavonoids.
There are thousands of different flavonoids, but they can be categorized in to 6 different classes:
- Flavonols: Their main function in plants is to provide protection from UV radiation and therefore are mainly found in the skin of fruits and vegetables
- Flavones: Mostly known for giving fruits and vegetables yellow and green coloring.
- Flavanones: The major polyphenol in citrus fruits
- Flavanols (Not Flavonols): These are also known as catechins (like in green tea).
- Anthocyanins: These give the beautiful red, blue and purple colors to plants.
- Isoflavones: These are a class of phytoestrogens, meaning although they are from plants, they have a similar structure and activity to estrogen in the body. The most well-known ones are likely soy-isoflavones.
The Proven Benefits
The Mediterranean Diet has been the focus of hundreds, if not thousands, of research studies over the last few decades. A recent “umbrella” review of many meta-analyses and randomized control trials of the Mediterranean Diet showed that there is significant evidence that a greater adherence to the Mediterranean Diet was associated with reduced risk of overall mortality, cardiovascular disease, coronary heart disease, myocardial infarction, overall cancer incidence, neurodegenerative disease and diabetes.
Another study, a subset of the PREDIMED (Prevention with the Mediterranean Diet) study, showed that high dietary polyphenol is associated with reduced all-cause mortality and lowered incidents of cardiovascular events. This was comparing the Mediterranean Diet to a low fat diet (which has a lower intake of polyphenols). This study actually was able to measure the polyphenol intake to those in the Mediterranean Diet arms and associate it with the improvement in clinical outcomes.
The MOLI-SANI study showed that the polyphenols in the Mediterranean Diet are associated with less low grade inflammation which is now thought to be the cause of many chronic diseases. This was measured through inflammatory markers such as CRP, WBCs and platelets. This cohort showed that a diet higher in polyphenols was related to a decrease in low grade inflammation.
Patient Adoption of the Diet
While adopting a “diet” may sound overwhelming, it is relatively simple to implement. One goal I give to patients is to “eat a rainbow everyday” with trying to encourage at least one serving each of fruit and vegetables with each main meal, and using fruits, vegetables, and nuts as snacks. Another relatively easy way to get more benefits of polyphenols is to switch from other cooking oils to extra virgin olive oil. Each time you eat is an opportunity to make a healthy decision with food.
 Menotti A, Keys A, Blackburn H, Kromhout D, Karvonen M, Nissinen A, et al. Comparison of multivariate predictive power of major risk factors for coronary heart diseases in different countries: results from eight nations of the seven countries study, 25 year follow-up. J Cardiov Risk. 1996;3:69–75.
 Oliveira R. The Power of Polyphenols? UC Davis Integrative Medicine. http://ucdintegrativemedicine.com/2015/07/the-power-of-polyphenols/#gs.EC1R_gs. Published August 8, 2017.
 Dinu M, Pagliai G, Casini A, Sofi F. Mediterranean diet and multiple health outcomes: an umbrella review of meta-analyses of observational studies and randomised trials. European Journal of Clinical Nutrition. 2017;72(1):30-43. doi:10.1038/ejcn.2017.58.
 Medina-Remón A, Casas R, Tressserra-Rimbau A, et al. Polyphenol intake from a Mediterranean diet decreases inflammatory biomarkers related to atherosclerosis: a substudy of the PREDIMED trial. British Journal of Clinical Pharmacology. 2016;83(1):114-128. doi:10.1111/bcp.12986.
 Bonaccio M, Pounis G, Cerletti C, Donati MB, Iacoviello L, Gaetano GD. Mediterranean diet, dietary polyphenols and low grade inflammation: results from the MOLI-SANI study. British Journal of Clinical Pharmacology. 2016;83(1):107-113. doi:10.1111/bcp.12924.