The seven country study about Mediterranean diet
The plan for this study was to identify coronary heart disease risk factors and disease rates. In 1958, Keys and his cohorts began examining nearly 13,000 men between the ages of forty and fifty-nine over a five-year period in Greece, Italy, Croatia and Serbia (at the time, both part of Yugoslavia), Japan, Finland, the Netherlands, and the United States. Rather than obtaining data through question-and-answer forms, dietitians were actually stationed in the homes of study subjects, measuring everything eaten and collecting samples to send back to Minnesota for chemical analysis. This type of hands-on data collection resulted in a dietary picture of the study subjects that was probably far more accurate than could ever be obtained via a questionnaire.
The extensive study included a follow-up period of an additional ten years on more than 10,000 men and examined a range of lifestyle factors in addition to diet and coronary heart disease rates.
The results of the now famous Seven Countries Study provided strong epidemiological evidence that, indeed, the percentage of calories from saturated fat is linked to in-creased blood cholesterol levels that result in an increased risk of coronary heart disease. Those countries with the highest consumption of saturated fat, such as the United States and Finland, had the highest rates of heart disease. The American men participating in the study, as well as the Finnish and Dutch men, had heart disease rates that were twice that of Italian men, and four times that of Greek, Japanese, and Yugoslav men (saturated-fat intake was, and still is, comparatively low in Greece, Japan, and Yugoslavia). Furthermore, the study determined that the rates of all-causes, age-specific death rates were among the lowest in the Mediterranean regions.
The Seven Countries Study also identified other key factors that appeared correlated with heart disease. These factors were age, blood pressure, and cigarette smoking. These factors, along with blood cholesterol, came to be known as “universal risk factors” for heart disease. Study after study continued to show that as these factors increased, so did the risk of heart disease. Of all of the identified risk factors, how-ever, blood cholesterol appeared to have the strongest correlation to heart disease.
Although a high saturated-fat diet (which appears to lead to high blood cholesterol levels) may not be, and probably isn’t, the sole factor in lower rates of coronary heart disease in the Mediterranean compared with the United States, Keys succinctly states, “The Mediterranean diet is certainly compatible with superior health.”
The investigation continues
Over the past few decades, research study after research study has confirmed the results of the Seven Countries Study: that a diet rich in fruits, vegetables, and whole grains, with low saturated fat, and monounsaturated fat as the primary fat, has been shown repeatedly to be beneficial to health and to decrease the risk of coronary heart disease and other chronic adult diseases such as diabetes and certain types of cancer. A study conducted in Lyon, France, led by Michael De Lorgeril, M.D., tested whether a Mediterranean-type diet high in omega-3 fatty acids might reduce the risk of a second heart attack in people who had had a previous heart attack.
The study, which came to be known as the Lyon Diet Heart Study, divided about six hundred patients who had recently had a heart attack, were under the age of seventy years old, and suffered no other medical or social ailments, into two groups. The first group, called the experimental group, was placed on a Mediterranean-type diet featuring fish, fruit, cereals, and beans, with about 30 percent of calories from fat. The main source of fat was canola oil, a good source of monounsaturated fat similar to olive oil. Only 8 percent of the calories in this diet were from saturated fat. The diet included about 200 milligrams of cholesterol.
The experimental group was given dietary and lifestyle counseling from health care professionals to ensure compliance. The other group, the control group, were given general low-fat diet instructions by their physicians to follow.
The study was originally scheduled to run for five years, but after a little over two years, the study was stopped. It appeared that the experimental group, the group consuming the Mediterranean-type diet, had far fewer cardiovascular complications than the control group. Therefore, it was deemed unethical to keep the highly beneficial Mediterranean diet a secret from the control group.
One of the most striking things about this study was that, after the researchers continued to track about 425 of the original study participants for another nineteen months, the original Mediterranean-diet group continued to eat a diet inspired by Mediterranean elements. They liked it that much!
And their cardiac health status continued to be much more favorable than that of those who were not following a Mediterranean-type diet. Patient compliance is often a difficult factor to obtain, so the fact that the experimental group kept eating the prescribed diet even after the study’s termination speaks volumes about both the health benefits and, presumably, the enjoyable nature and palatability of a traditional Mediterranean diet.
Research refining the health benefits of various aspects of the Mediterranean diet has been plentiful. The nature of different types of fats has been discovered. For instance, trans-fatty acids—which are found in processed foods containing hydrogenated or partially hydrogenated vegetable oils such as margarine—have been shown to increase heart disease risk. Omega-3 fatty acids, available in fish and from certain vegetable sources like flax seed, have been shown to decrease the blood’s tendency to clot, thereby decreasing heart attack risk. Monounsaturated fats, of which olive oil and canola oil are rich sources, have been shown to lower “bad” LDL cho-lesterol, and promote “good” HDL cholesterol.
Fat isn’t the only component of the Mediterranean diet that seems to be so compatible with good health. The discovery of phytochemicals, the wide array of chemical com-pounds in plant foods, has prompted a new revolution in nutrition science. The benefits of fiber, antioxidants, and other treasures available to the body through the consumption of plant foods continually interest nutrition science
Recently, there has been a lot of focus on refined carbohydrates as being promoters of heart disease, as well as diabetes and obesity. Researchers are pointing out that the body metabolizes sources of refined grains—white bread, sugary cereals, and processed snack items, for example—the same way it processes sugar, by causing a rapid rise in blood sugar, or blood glucose. Unless a person burns off the sugar present in his or her system through activity, insulin is released by the body to take the glucose out of the blood stream and into fat cells for storage. If the body keeps get-ting flooded with refined carbohydrates and sugar, its sugar-removal system begins to break down, resulting in more and more insulin production. This puts the body at risk for developing diabetes, obesity, and heart disease.
Our bodies metabolize whole-grain products (whole-grain bread, pastas, and cereals) differently, digesting them more slowly so that blood glucose levels rise more slowly. This is a more natural way to get energy and is less extreme, or more “gentle” on the system.
In the traditional Mediterranean diet, as observed by Ancel Keys and others, refined grain products were virtually nonexistent because the technology simply was not there to process whole grains into refined grain products. Sweetness in the traditional Mediterranean diet came from succulent fruits, not from processed sugars.
Of course, no one nutrient or even a single food group holds the secret to perfect health. Instead, a combination of factors, from fresher and more abundant produce to whole grains and a lower intake of fat from animal sources, to a change in attitude, lifestyle, and activity level, seem to contribute to greater heart health, lower cancer risk, healthy long-term weight control, and longer life.
The particular “magic” of the traditional Mediterranean diet is just such a combination of factors. Not just monoun-saturated fats such as olive oil. Not just whole grains instead of refined. Not just a lower intake of animal products and a higher intake of legumes, nuts, and seeds. Not just fish. Not just the small daily dose of wine with dinner. Instead, all these factors together, resulting in a low overall fat intake with a specific saturated-to-monounsaturated fat ratio, a higher fiber intake, and what amounts to a wide array of phytochemical benefits from daily plant foods, create a nutritional plan that can improve anyone’s health.