The Secret Behind the Mediterranean DietJanuary 2010
By Dale Kiefer
The Mediterranean diet is one of the healthiest ways to eat on the planet. It’s rich in fiber, fruits-vegetables, and heart-healthy omega-3 fatty acids.
You may be surprised to learn, however, that many of its benefits emanate from just one of its components: olive oil.1,2 Emerging scientific evidence suggests that along with other foods found in the Mediterranean diet, specific olive oil compounds—olive oil polyphenols—enhance the diet’s health-promoting effects.
For thousands of years, people in Mediterranean countries have eaten a diet rich in fresh fruits and vegetables, whole grains, nuts and legumes, fish, wine, olive oil, and lean meat. The benefits of this approach are well-documented. They range from a reduction in cardiovascular disease risk to lower incidence of neurological disorders, cancer, and even age-related bone loss.3-15
Recent clinical studies indicate that these benefits result from the combined effect of the polyphenols such as hydroxytyrosol found in olive oil, in conjunction with omega-3 from fish, resveratrol from red wine, beta-sitosterols abundant in plant foods, and other constituent compounds of the Mediterranean diet.16
The Power of Olive Oil Polyphenols Revealed
Experts have long assumed that the monounsaturated fat content in olive oil is responsible for most of its health benefits. But a growing body of evidence suggests that the collective effects of olive oil polyphenols are just as important.
In 2007, Spanish researchers published a review of multiple clinical trials looking at various aspects of olive oil polyphenolic compounds’ effect on health. The reviewers noted that monounsaturated fat alone could not account for all the observed benefits.
“Perhaps a high oleic acid intake is not the sole primary [agent] responsible for the healthy properties of olive oil,” the authors wrote. If this were the case, any rich source of monounsaturated fats, such as non-virgin olive oil, or rapeseed/canola oil, would provide the same benefits as extra virgin olive oil, they argued.17
Another large study indicated that polyphenols are the nutritional “secret weapons” in olive oil. This large, multicenter clinical trial involving 200 subjects from five European countries, examined the effects of daily olive oil consumption on oxidative damage.18
Three different kinds of olive oil were used, each with increasing concentrations of polyphenols.18 Participants were randomly given about 0.84 fluid ounces of one of the olive oils each day for three weeks.
Investigators found that all the olive oils increased beneficial high-density lipoprotein (HDL) levels. All three also decreased plasma triglycerides.18
Consumption of medium- and high-phenolic-content olive oil favorably influenced the total cholesterol/HDL ratio and reduced levels of oxidized low-density lipoprotein (LDL).18 “The greatest effects on increasing HDL-cholesterol levels and decreasing lipid oxidative damage were observed after [consumption of] high-phenolic olive oil,” researchers noted.19 This led them to conclude that the polyphenols, rather than monounsaturated fat alone, are responsible for olive oil’s multiple benefits.
Olive Oil Works with Omega-3 to Prevent Atherosclerosis
Many of the anti-inflammatory and cardioprotective benefits of the Mediterranean diet come from the omega-3s from fish and other seafood in the Mediterranean diet. However, recent scientific evidence showed that when consumed in combination, omega-3 fatty acids and olive oil polyphenols confer greater benefits than either nutrient alone.20-24
In July 2009, scientists presented data regarding atherosclerosis prevention in a preclinical model of atherosclerotic disease. Norwegian researchers used a blend of marine omega-3 fatty acids and extra virgin olive oil and the progression of atherosclerotic lesions was subsequently assessed.23
Lesion formation was reduced by 54% in the aorta and 61% in the aortic arch of the female animals studied. Among males, significant reductions in lesion sizes were observed solely in the thoracic and abdominal aortas.23
“This effect seemed to be [independent of] lipid metabolism and platelet aggregation,” they concluded. “Hence, dietary supplementation of such an oil mixture may be valuable in the prevention of atherosclerotic vascular diseases.”23
Heart Health Benefits Comparable to Aspirin
Physicians routinely recommend that patients at risk for cardiovascular disease take low-dose aspirin because of its anti-clotting and anti-inflammatory action, which reduces the risk of a heart attack or ischemic stroke. Olive oil polyphenols may work just as well.25,26
A recent study demonstrated that olive oil polyphenols decrease the “stickiness” of blood platelets as effectively as aspirin, lowering the risk of clotting.26 The olive oil polyphenol hydroxytyrosol acetate inhibits synthesis of the body’s natural clotting factor, according to the British Journal of Nutrition.26
A clinical trial performed on healthy male volunteers revealed similar findings. Subjects consumed olive leaf extract before submitting blood samples for analysis. Tests revealed a significant dose-dependent reduction in platelet activity with olive extract.25
Dietary olive oil polyphenols have also been shown to significantly lower experimentally-induced inflammation.27 Laboratory rats fed a diet rich in olive polyphenols have shown markedly diminished indicators of inflammation, compared to rats fed olive oil with no polyphenols.
Animals with adjuvant arthritis, a model of chronic inflammation, also fared better on a diet rich in polyphenols compared to those on diets without them. Olive oil polyphenols have even been shown to augment the effects of the anti-inflammatory drug indomethacin in pre-clinical models.27