The study included 7447 people between 55 and 80 years of age. All of the participants were at high risk for heart attack or stroke, assigned to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or, as a control, a diet in which they ate whatever they wanted but were advised to limit their fat intake as much as they could. After about five years the incidence of heart attack, stroke and cardiovascular cause-related deaths among the groups were compared.
They found that an “energy-unrestricted” Mediterranean diet supplemented with either extra virgin olive oil or nuts decreased cardiovascular disease risk by 30 percent in people at high risk for the disease. A closer analysis of the data showed, however, that while the overall risk for cardiovascular events was decreased, the Mediterranean diet helped to prevent stroke, but not heart attack (myocardial infarction). The researchers are unsure if the diet’s protection against stroke but not against heart attack reflects a real difference in the diet’s effects on body physiology or having too few test subjects to, regarding protection against heart attacks, reach statistical significance.
While a 30 percent drop in cardiovascular events is always a good thing, in terms of absolute numbers, it’s not that much of a difference. A 30 percent decrease means if 1,000 people switched to a Mediterranean diet for one year, there would only be three fewer people who’d suffered cardiovascular events.interview with the New York Times, and added, “the really important thing – the coolest thing – is that they used very meaningful endpoints. They did not look at risk factors like cholesterol or hypertension or weight. They looked at heart attacks and strokes and deaths. At the end of the day, that is what really matters.”
Past research has suggested that the Mediterranean diet was the way to go. A large survey of the literature from 2009 ranking tens of different types of diets placed the Mediterranean diet as the most protective against coronary heart disease. But the ranking was based largely on studies showing that people in the Mediterranean tended to have lower rates of heart disease, which could have been due to other factors besides diet.
The traditional mediterranean diet includes high amounts of olive oil, nuts, fruit, vegetables, and cereals, moderate amounts of fish and poultry and low amounts of red and processed meats, dairy products and sweets. And moderate amounts of wine during dinner, of course. We are in the Mediterranean after all. But as of yet, there’s no consensus among scientists as to why these foods would protect us against what is the leading cause of death for both men and women in the United States. It is thought that, perhaps, a kind of synergy among the nutrient-rich foods favorably affects the underlying elements that influence cardiovascular health, like levels of lipids in the blood, insulin sensitivity, oxidative stress levels, and inflammation.
“Food synergy” is a relatively new concept in nutrition that attempts to assess the health effects of food as a whole rather than the sum of its nutritional parts. It is based on the idea that the interactions between constituents in food are important, that these constituents eaten from their natural biological sources affect the body differently than taken alone as supplements. So, what “food synergy” sounds like to me is a kind of hand-waving way to say: it’s complicated. Minerals, vitamins, antioxidants, and other supplements we put in our bodies to be healthy aren’t turning out to be the cell-, heart- and brain-protecting powers they were thought to be in the ‘90s (although the companies selling these supplements certainly haven’t noticed).
And so, because it’s complicated, it’s not clear why a diet loaded with oils and nuts high in calories is good for the cardiovascular system. Despite the measurable evidence, experts in the past have been hesitant to recommend a Mediterranean diet to many people at risk for cardiovascular problems because they were also overweight. Indeed, in the study people who did not lose any weight while on the diet still reaped the health benefits. The body’s complicated, and so is food. But thankfully we have studies like the current one that tests and idea even if there’s no obvious way to explain it.