Good Calories, Bad Calories

intake group and 16 in the low-fat group.”

Two decades later, Jeremiah Stamler and his colleague Richard Shekelle from Rush–Presbyterian–St. Luke’s Medical Center in Chicago revisited Western Electric to see how these men had fared. They assessed the health of the employees, or the cause of death of those who had died, and then considered the diets each subject had reportedly consumed in the late 1950s. Those who had reportedly eaten large amounts of polyunsaturated fats, according to this new analysis, had slightly lower rates of coronary heart disease, but “the amount of saturated fatty acids in the diet was not significantly associated with the risk of death from [coronary heart disease],” they reported. This alone could be considered a refutation of Keys’s hypothesis.

But Stamler and Shekelle knew what result they should have obtained, or so they believed, and they interpreted the data in that light. Their logic is worth following. “Although most attempts to document the relation of dietary cholesterol, saturated fatty acids, and polyunsaturated fatty acids to serum cholesterol concentration in persons who are eating freely have been unsuccessful,” they explained, “positive results have been obtained in investigations besides the Western Electric Study.” They then listed four such studies: a new version of Keys’s study on Japanese men in Japan, Hawaii, and California; a study of men living for a year at a research station in Antarctica; a study of Tarahumara Indians in the Mexican highlands; and one of infants with a history of breast-feeding. To Stamler and Shekelle, these four studies provided sufficiently compelling support for Keys’s hypothesis that they could interpret their own ambiguous results in a similar vein. “If viewed in isolation,” they explained, “the conclusions that can be drawn from a single epidemiologic study are limited. Within the context of the total literature, however, the present observations support the conclusion that the [fat] composition of the diet affects the level of serum cholesterol and the long-term risk of death from [coronary heart disease, CHD] in middle-aged American men.”

The New England Journal of Medicine published Stamler’s analysis of the Western Electric findings in January 1981, and the press reported the results uncritically. “The new report,” stated the Washington Post, “strongly reinforces the view that a high-fat, high-cholesterol diet can clog arteries and cause heart disease.” Jane Brody of the New York Times quoted Shekelle saying, “The message of these findings is that it is prudent to decrease the amount of saturated fats and cholesterol in your diet.” The Western Electric reanalysis was then cited in a 1990 joint report by the American Heart Association and the National Heart, Lung, and Blood Institute, entitled “The Cholesterol Facts,” as one of seven “epidemiologic studies showing the link between diet and CHD [that] have produced particularly impressive results” and “showing a correlation between saturated fatty acids and CHD,” which is precisely what it did not do.^*7

In preventive medicine, benefits without risks are nonexistent. Any diet or lifestyle intervention can have harmful effects. Changing the composition of the fats we eat could have profound physiological effects throughout the body. Our brains, for instance, are 70 percent fat, mostly in the form of a substance known as myelin that insulates nerve cells and, for that matter, all nerve endings in the body. Fat is the primary component of all cell membranes. Changing the proportion of saturated to unsaturated fats in the diet, as proponents of Keys’s hypothesis recommended, might well change the composition of the fats in the cell membranes. This could alter the permeability of cell membranes, which determines how easily they transport, among other things, blood sugar, proteins, hormones, bacteria, viruses, and tumor-causing agents into and out of the cell. The relative saturation of these membrane fats could affect the aging of cells and the likelihood that blood cells will clot in vessels and cause heart attacks.

When we consider treating a disease with a new therapy, we always have to consider potential side effects such as these. If a drug prevents heart disease but can cause cancer, the benefits may not be worth the risk. If the drug prevents heart disease but can cause cancer in only a tiny percentage of individuals, and only causes rashes in a greater number, then the tradeoff might be worth it. No drug can be approved for treatment without such consideration. Why should diet be treated differently?

The Seven Countries Study, which is considered Ancel Keys’s masterpiece, is a pedagogical example of this risk-benefit problem. The study is often referred to as “landmark” or “legendary” because of its pivotal role in the diet-heart controversy. Keys launched it in 1956, with $200,000 yearly support from the Public Health Service, an enormous sum of money then for a single biomedical research project. Keys and his collaborators cobbled together incipient research programs from around the world and expanded them to include some thirteen thousand middle- aged men in sixteen mostly rural populations in Italy, Yugoslavia, Greece, Finland, the Netherlands, Japan, and the United States. Keys wanted populations that would differ dramatically in diet and heart-disease risk, which would allow him to find meaningful associations between these differences. The study was prospective, like Framingham, which means the men were given physical examinations when they signed on, and the state of their health was assessed periodically thereafter.

Results were first published in 1970, and then at five-year intervals, as the subjects in the study aged and succumbed to death and disease. The mortality rates for heart disease were particularly revealing. Expressed in deaths per decade, there were 9 heart-disease deaths for every ten thousand men in Crete, compared with 992 for the lumberjacks and farmers of North Karelia, Finland. In between these two extremes were Japanese villagers at 66 per ten thousand, Belgrade faculty members and Rome railroad workers at 290, and U.S. railroad workers with 570 deaths per ten thousand.

According to Keys, the Seven Countries Study taught us three lessons about diet and heart disease: first, that cholesterol levels predicted heart-disease risk; second, that the amount of saturated fat in the diet predicted cholesterol levels and heart disease (contradicting Keys’s earlier insistence that total fat consumption predicted cholesterol levels and heart disease with remarkable accuracy); and, third, a new idea, that monounsaturated fats protected against heart disease. To Keys, this last lesson explained why Finnish lumberjacks and Cretan villagers could both eat diets that were 40 percent fat but have such dramatically different rates of heart disease. Twenty- two percent of the calories in the Finnish diet came from saturated fats, and only 14 percent from monounsaturated fats, whereas the villagers of Crete obtained only 8 percent from saturated fat and 29 percent from monounsaturated fats. This could also explain why heart-disease rates in Crete were even lower than in Japan, even though the Japanese ate very little fat of any kind, and so very little of the healthy monosaturated fats, as well. This hypothesis could not explain many of the other relationships in the study—why eastern Finns, for instance, had three times the heart disease of western Finns, while having almost identical lifestyles and eating, as far as fat was concerned, identical diets—but this was not considered sufficient reason to doubt it. Keys’s Seven Countries Study was the genesis of the Mediterranean-diet concept that is currently in vogue, and it prompted Keys to publish a new edition of his 1959 best-seller, Eat Well and Stay Well, now entitled How to Eat Well and Stay Well the Mediterranean Way.

Despite the legendary status of the Seven Countries Study, it was fatally flawed, like its predecessor, the six- country analysis Keys published in 1953 using only national diet and death statistics to support his points. For one thing, Keys chose seven countries he knew in advance would support his hypothesis. Had Keys chosen at random, or, say, chosen France and Switzerland rather than Japan and Finland, he would likely have seen no effect from saturated fat, and there might be no such thing today as the French paradox—a nation that consumes copious saturated fat but has comparatively little heart disease.

In 1984, when Keys and his colleagues published their report on the data after fifteen years of observation, they explained that “little attention was given to longevity or total mortality” in their initial results, even though what we really want to know is whether or not we will live longer if we change our diets. “The ultimate interest being prevention,” they wrote, “it seemed reasonable to suppose that measures controlling coronary risk factors would improve the outlook for longevity as well as for heart attacks, at least in the population of middle-aged men