Oiling the Mechanism of Your Heart
One of the major frustrations in trying to identify specific dietary factors that may affect the health of the heart is that human beings cannot be treated like laboratory animals. Sure, you can get 20 volunteers and add something or subtract something from their diet for six weeks, and you can measure the changes in their serum cholesterol or whatever over that time. But what really matters is how your health and your heart are affected for better or worse, which in practical terms means that you would have to track a group of people for at least five years before any notable trends became obvious. Even more difficult—you would have to figure out some way of making sure that all those people stuck to whatever diet you put them on.
One of the few studies to break through this wall of frustration was designed to clarify the effect of different oils on the heart. Scientists in Finland solved the logistics of such a study by conducting it in mental hospitals, using only long-term patients, whose diet was beyond their personal control, and who could easily be followed for many years. We might add that the fact that this study was carried out in Finland was no accident, since that country has the distinction of having the highest heart attack rate in the world, a statistic usually linked with the high concentration of saturated fats from dairy products, meat and eggs in the Finnish diet.
In one mental hospital, long-term patients were given the normal Finnish diet. In another hospital, much of the saturated fat was replaced with polyunsaturated fat, substituting margarine for butter, for instance. After six years, the diets were switched, and the patients who had been on the experimental polyunsaturated diet went back to eating the typical Finnish diet.
The results were more dramatic than the researchers probably expected. The rate of death from coronary heart disease in the hospital on the experimental diet fell to half the rate at the other institution. When the diets were switched so were the heart attack statistics (Circulation, January, 1979).
A few years later, a short-term study was carried out once more by Finnish researchers, this time in the county of North Karelia, which has a high rate of coronary heart disease and a very high prevalence of high cholesterol. The researchers wanted to find out if that reflected the result of a diet rich in animal fats or was simply the result of hereditary factors. For six weeks, a group of volunteers ate a diet that was low in saturated fats but relatively high in polyunsaturates. Milk and butter were replaced by skim milk and vegetable oil and margarine. The volunteers were urged to eat lean meat, fish, poultry and special low-fat sausage and cheese instead of the regular fatty meat, sausage and cheese. The use of vegetables, and of fruits and berries, was also strongly encouraged by nutritionists.
In just six weeks of following such a diet, the average cholesterol level in men fell from 263 to 201; in women, from 239 to 188. When the volunteers went back to their regular diet, blood lipid levels for the most part went right back to where they had been before—strong evidence that diet, and not heredity, was plaguing the circulation of these North Karelian (New England Journal of Medicine, September 30, 1982).
The very same month that the above study appeared in medical literature, so did another study, this one from researchers at Oxford University. The subjects were 32 men who had had heart attacks within the preceding five days. All were given special blood tests to analyze the relative amounts of different kinds of fats in their blood. It was determined that compared to other men of similar age who had not had heart attacks, these men had unusually low levels of the polyunsaturated fat known as linoleic acid in various fractions of their blood. It was further determined that this difference was not caused by the heart attacks, but rather reflected long-term dietary habits. Apparently, blood cells with a relatively low amount of polyunsaturated linoleic acid are more likely to clot, causing a thrombosis, than blood cells that are adequately supplied with this fat. In short, said the researchers, “Our study provides strong evidence that a diet relatively rich in linoleic acid may be protective against myocardial infarction [heart attack]” (British Medical Journal, September 11, 1982).
No one yet knows the optimal amount of polyunsaturated fat that one ought to eat to derive this apparent protection. One thing many experts agree on, though, is that what you don’t want to do is drown in the stuff. A tablespoon or so of corn, sunflower or safflower oil on your daily salad is probably in the neighborhood of being an appropriate amount. Nuts, seeds and whole grains such as wheat and corn, as well as wheat germ and lecithin, also supply polyunsaturates. But please remember this: Putting a tablespoon of vegetable oil on your salad may not do you all that much good if the rest of your dinner consists of a big fatty steak, a baked potato topped with sour cream, and apple pie and ice cream for dessert.