From Chapter 10: The Food Pyramid

Cardiovascular Health and The Mediterranean Diet


Mediterranean populations, for centuries, have enjoyed a low cardiovascular disease risk in comparison to their Northern European counterparts. While researchers have found several factors that contribute to this difference, the primary reason is the so-called Mediterranean diet.

For decades epidemiologists studying the dietary habits of the Mediterranean region were asking the same question: How can the peoples of a country like Crete enjoy an excellent state of health when 40% of their daily energetic requirements are met through the intake of fats?

A high fat diet is also typical of Finland, but in comparison the country maintains a high rate of coronary heart disease. It, therefore, appears that besides quantity, the quality of fats in the diet plays a determining role in one's state of health. The unifying feature of most Mediterranean populations is the broad use of olive oil as a main source of fat. This substitutes for the saturated animal fats so typical in northern European cuisine.

Saturated fats and dietary cholesterol tend to increase the levels of blood cholesterol, the polyunsaturated vegetable oils and fish oils tend to lower cholesterol, while the monounsaturated oils (olive oil) are neutral.

Thinking only in terms of total cholesterol circulating through the bloodstream may be misleading. We now know that there are different kinds of cholesterol, some can be harmful to arteries (the low-density lipoproteins [LDL] for instance), while others are protective. The high-density lipoproteins (HDL) make up a small part of total cholesterol, about 20%, but are inversely correlated with coronary heart disease. In other words, the higher the HDL, the lower the risk of heart disease. Expressing the concept with the total cholesterol/HDL ratio, the lower the ratio the lower the risk. Decreasing total cholesterol and/or increasing HDL will have that effect. This occurs whenever the intake of monounsaturated or polyunsaturated fats is greater and when saturated fat intake is low.

All fats by nature tend to increase cholesterol and thus HDL, except polyunsaturated hydrogenated oils contained in some vegetable margarine. Such fats are termed "trans," perhaps because innocuous agents mask them.

A good supply of monounsaturated and polyunsaturated fats appears to be crucial for a correct diet. Olive oil is rich in monounsaturated fatty acids (oleic acid) and less rich in polyunsaturated fatty acids, especially the omega-3 fatty acids. An alternative source of protective omega-3 may be found in fish, or some vegetables (rapeseed, linseed, soybean, and nuts).

Vegetable oils supply important tocopherol for the diet. Olive oil contains approximately 12 milligrams of alpha-tocopherol (vitamin E) for every 100 grams of oil. The union between a diet rich in monounsaturated fats and discrete amounts of vitamin E may protect against arteriosclerosis.

Although several studies of the past suggested that the substitution of saturated fats in the diet with polyunsaturated fats could prevent vascular disease, no study had evaluated the effect of a Mediterranean diet on the incidence of heart disease. It took the French Lyon Diet Heart Study to compare the cardiovascular effects of two different diets in subjects who had had a myocardial infarction. The experimental group with 302 subjects followed a typical Mediterranean diet with a percentage of total fat less than 35%, saturated fat less than 10%, monounsaturated fat more than 10%, linoleic acid (omega-6) less than 4% and a second linolenic acid (omega-6) greater than 0.6%, with a omega-6/omega-3 ratio of about 5.

The following six dietary guidelines were given to the experimental group.
· Increase bread intake
· Increase vegetables and legumes
· Increase fish
· Less red meat (beef, pork, horse) and more poultry
· Daily fruit intake
· No butter or creams, substituting special margarine

Because a Mediterranean diet had to be, by definition, rich in monounsaturated fatty acids, the French investigators had to face the problem of forcing ample amounts of olive oil (an average of 25 grams per day) on their co-nationals. This was a cultural aspect difficult to overcome. To achieve this, in fact, they ultimately selected rapeseed oil, as it possesses the same characteristics as olive oil, and presented it as margarine. This allowed the French to have their spread.

At the end of only two months, the mortality curve between the two groups began to fork. The group treated with the Mediterranean diet had fewer deaths than the group on standard diet (more polyunsaturated omega-6 oils coupled with a traditional post-infarction diet). Forty-six months after the study began, the Mediterranean diet reduced mortality by 70 percent.

To lower cholesterol, Western society diets are traditionally based on polyunsaturated fatty acids instead of saturated fats. A polyunsaturated fatty acid such as linoleic acid found in corn and sunflower oils is thus recommended. Linoliec acid has 18 carbon atoms (C18), with two double bonds (2n) and belongs to the omega-6 series (18:2n-6). But linoleic acid can have undesired side effects. It favors the oxidation of LDL that promotes arteriosclerosis and increases platelet aggregation. Linolenic acid, on the other hand, belongs to the omega-3 series of fatty acids (18:3n-3) and is plentiful in rapeseed, soybean, linseed and dried nuts. It is interesting to note that the two populations of the world with the longest life spans, the people from the island of Crete and the Japanese from the island of Kohama, seem to eat the most linolenic acids.

The Lyon Diet Heart Study provided us with the first demonstration that a Mediterranean diet, such as that eaten on Crete, although adapted to a western population, protects the heart more than a standard post-infarction diet. A lower intake of saturated fats, a higher intake of oleic acid (found in olive and rapeseed oils), natural antioxidants (occurring in fruit and vegetables) and linolenic acid, associated with little meat and wine, are very likely winning combinations. They show that a global approach to eating is worth more than a single choice. The findings are even more impressive when we consider that the French already have one of the lowest cardiovascular disease rates in the world. For men it is second only to the Japanese.

It is hoped that a diet with the same characteristics as that used in the French study can be used elsewhere and not only in the populations with a high risk of heart disease. Roughly 50% of the people living in Western countries are destined to die of heart disease, especially heart attack. Since most people ignore their destiny, it would be wise to install preventive eating habits.

Epidemiological investigations carried out on populations living in Western countries indicate that an excessive intake of red meat--veal, pork, and lamb-is associated with an increased incidence of chronic and degenerative diseases including heart disease and some cancers (colon, perhaps prostate, and others). The most consistent evidence for this association is provided by the comparison of disease rate between Seventh Day Adventists who eat meat rarely or not at all, and non-vegetarians, who eat meat daily. The latter have a 60% greater likelihood of dying from coronary heart disease.

It is still unclear whether it is the fat in meat that solicit these harmful effects. Carcinogens could form during cooking, especially by grilling, cooking over a flame, or frying. Then there are nitrosamines, suspected source of all our troubles, were first identified in burned meat and can induce tumors in laboratory animals. It seems, however, that these substances are not responsible for tumors in humans. Hence, the mechanisms that underlie carcinogen-mediated tumor initiation after a rich meat diet remain a mystery.

Meat contains little fiber and has no natural antioxidants. Eating meat on a daily basis frequently means that you eat fewer vegetables, which are rich in antioxidants. Red meat is also the leading source of methionine in the diet. This amino acid is the direct metabolic precursor of homocysteine, another amino acid, which does not become a building block of protein, but is harmful to arteries. It is also plausible, through not demonstrated, that a high intake of meat can raise levels of homocysteine in the bloodstream.

Bearing this in mind, the dietary guidelines established by the American Department of Agriculture in recent years is unconvincing. These guidelines recommended, for example, eating 140-196 grams of meat per day in a healthy diet.

Traditionally, Mediterranean populations eat little meat and have fewer health risks, but most important of all, have individual and public health profiles that are far better than those found in industrialized nations that eat more meat.

The amount of fish eaten among Mediterranean peoples varies. The Spanish, the Portuguese and the inhabitants of Corfu eat the most. The people living in Southern Italy and Crete eat the least fish. Such a finding, in theory, should suggest a marginal role for fish in the Mediterranean diet. However, clinical studies disprove this view.
To illustrate the cardiovascular effects of eating fish we can examine a recent study in the USA. The eating habits for a large group of American male physicians (nearly 20,000) were followed in a 12-year study. Those who ate fish at least once a week presented a risk of sudden death 30-40% lower than those who ate fish less than once a month. The fatty acids in fish belongs to the omega-3 series (like linolenic acid), but the names are more complicated; for instance, eicosapentaenoic acid and docosaesaenoic acid. It is likely that these fatty acids replace linoleic acid (omega-6) in the lipid bilayer of the cell membrane, stabilizing changes in cardiac rhythm that may cause sudden death.

The conclusion of recent studies indicates what Mediterranean populations have known, indirectly, for centuries. The use of natural, monounsaturated oils such as olive oil, a balanced intake of vegetables and fish, with a low intake of red meats, provides a natural defense against cardiovascular disease. The Mediterranean diet is a healthy diet, no matter where one lives.

11 Keys of a Mediterranean Diet

1. Diet and eating
a. Eat a balanced diet that is varied and based on vegetable matter.
b. Favor a diet rich in fruit, vegetables and non-refined starchy food.

2. Body weight
a. Body mass index (weight in kilograms divided by height in square meters) in adults must be kept on the average between 21 and 24, considering 18.5 and 25 as the lower and upper limits, respectively.

3. Physical fitness
a. Be physically active and adopt an active lifestyle.
b. Should your job increase a sedentary lifestyle, take a daily walk for about an hour or take up an activity equal to at least one hour of gymnastics per week that uses the whole body.

4. Fruit and vegetables
a. Make vegetables at least 7% of your dietary calories.
b. Eat 400-800 grams or five portions of fruit and vegetables per day all year long.

5. Other vegetable foods
a. Include foods that are rich in proteins, starch (better when unrefined) until you cover 45-60% of calories eaten. Refined sugar must not exceed 10% of your calories.
b. Eat 600-800 grams or at least seven portions a day of assorted cereals, legumes, tubers, and roots. They are best when milled the least. Limit the amount of unrefined sugar.

6. Alcoholic beverages
a. No alcohol is advisable and every excess must be avoided. For those who are used to drinking, 5% of the calories for men and 2.5% for woman are sufficient.
b. Up to two glasses of wine a day for men, and one glass of wine for women at mealtime is permissible.

7. Meat
a. The amount of protein coming from red meat must not exceed 10% of the total protein in the diet.
b. If you do not intend to give up red meat, the total contribution of calories should not exceed 80 grams per day. Chicken, game, or fish is a better choice.

8. Fats and Oils
a. The total fatty acids must assure a supply of calories between 15 and 30% of the total calorie intake.
b. Limit the use of fatty foods, especially those containing animal fats. Season with vegetable oil, above all with olive oil.

9. Salt
a. The total amount of salt for an adult must not exceed 6 grams per day.
b. Restrict salt in cooking, eating salty foods and table salt. Use herbs to flavor fresh foods.

10. Preparation
a. It is advisable to cook meat or fish at low temperature.
b. Avoid burning sauces. Fish and meal grilled directly over an open fire and smoked meats should only be eaten occasionally.

11. Dietary supplements
a. A balanced diet is sufficiently protective and does not require food additives.
b. Follow these recommendations and supplements should be unnecessary.