Landmark clinical trial provides strong evidence in favor of the traditional Mediterranean diet
by Craig Weatherby
According to a survey by the American Heart Association, one in three Americans suffered from some form of cardiovascular disease (CVD) in 2002. But there’s ample evidence that relevant diet and lifestyle changes can reduce those risks as much or more than costly synthetic drugs with unknown long-term effects.
Ever since the results of the groundbreaking Seven Countries Study began to trickle out in the 1960’s, evidence that traditional rural diets in Greece and Italy protect heart health has continued to accumulate. And these cardiovascular advantages seem especially strong among people living in their Mediterranean coastal areas and on Aegean islands, thanks to their exceptionally fish-rich diets.
Basic and human research conducted since the Seven Countries study suggest that the cardiovascular benefits of classic Mediterranean diets flow from their abundance of helpful foods and their avoidance of problematic ones (See “Fish Inhibits Heart-Attacking Inflammation” and “Extra Virgin Olive Oil Seen Superior for Reducing Cardiac and Cancer Risks”).
While they vary, Mediterranean diets share two relevant attributes:
- Rich in anti-inflammatory, antioxidant foods: Fish, vegetables, culinary herbs, and extra virgin olive oil. Note: Refined, “pure” grade olive oil lacks the potent antioxidants in unrefined “extra virgin” oil and is far less heart-healthy.
- Low in pro-inflammatory foods: Red meat, refined grains, and omega-6-rich cooking oils and processed foods.
When it comes to heart-health, many researchers hypothesize that low-fat diets are counterproductive, because they tend to leave people shy of their need for the essential, anti-inflammatory omega-3 fats—and, in the context of Mediterranean diets—the powerfully anti-inflammatory antioxidants in extra virgin olive oil—needed to maintain or enhance cardiovascular health.
Accordingly, the authors of a solid new study from Spain decided to test the heart-health powers of the classic Mediterranean diet against those of a low-fat diet. This pioneering epidemiological study followed the participants over a period of four years, rather than the several months or less in similar prior investigations.
And the results of this relatively rigorous Spanish research support the cardiovascular superiority of traditional Mediterranean diets versus extreme very-low-fat diets like the one developed by Dr. Dean Ornish.
Spanish findings place Mediterranean diets first
A Spanish team at the Hospital Clinic of Barcelona recruited 772 adults at high risk of cardiovascular disease (CVD), and divided them into three groups. One group agreed to eat a low-fat diet, and the other two groups ate the classic Mediterranean diet, but were given either free nuts or free olive oil, which presumably caused them to consume more than normal.
Risk factors and heart-health status such as body weight, blood pressure, lipid profile, glucose levels and inflammatory molecule levels were recorded every three months, and almost all of the participants completed the four-year trial.
Compared with the group placed on low-fat diets, both Mediterranean-diet groups enjoyed greater improvements in blood glucose levels, systolic blood pressure levels, and their ratio of total cholesterol to HDL (“good”) cholesterol.
As the Spaniards said, “Compared to a low-fat diet, Mediterranean diets supplemented with olive oil or nuts have beneficial effects on cardiovascular risk factors.”
Olive oil proves more powerful than nuts
Interestingly, there were differences between the two Mediterranean diet groups:
- The group that received free virgin olive oil enjoyed greater decreases in blood glucose levels, greater improvements in the ratio of total cholesterol to HDL cholesterol, and significant reductions in their blood levels of C-reactive protein (a marker of inflammation linked to heart disease).
- The group that received free nuts enjoyed greater reductions in systolic blood pressure.
Team leader Emilio Ros, M.D. expressed confidence that these changes would benefit people’s health: “We expect it to reduce the rates of heart attacks and strokes and other cardiovascular diseases by 50 percent.”
We regret that (probably for financial reasons) the trial did not include a fourth, “free fish” group. Compared with omega-3s from nuts and seeds, omega-3s from fish possess far stronger evidence of cardiovascular benefit. We suspect that the advantages over the low-fat group would peak among people eating a Mediterranean diet especially rich in fish.
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