After the AHA report hit the press, Time quickly enshrined Keys on its cover as the face of dietary wisdom in America. As Time reported, Keys believed that the ideal heart-healthy diet would increase the percentage of carbohydrates from less than 50 percent of calories to almost 70 percent, and reduce fat consumption from 40 percent to 15 percent. The Time cover story, more than four pages long, contained only a single paragraph noting that Keys’s hypothesis was “still questioned by some researchers with conflicting ideas of what causes coronary disease.”
Chapter Two
THE INADEQUACY OF LESSER EVIDENCE
Another reason for the confusion and contradictions which abound in the literature concerning the etiology of coronary artery disease is the tyranny that a concept or hypothesis once formulated appears to exert upon some investigators in this field. Now to present, to emphasize, and even to enthuse about one’s own theory or hypothesis is legitimate and even beneficial, but if presentation gives way to evangelistic fervor, emphasis to special pleading, and enthusiasm to bias, then progress is stopped dead in its tracks and controversy inevitably takes over. Unfortunately it must be admitted that in the quest to determine the causes of coronary artery disease, these latter deteriorations have taken place.
MEYER FRIEDMAN, Pathogenesis of Coronary Artery Disease, 1969
FROM THE 1950S ONWARD, researchers worldwide set out to test Ancel Keys’s hypothesis that coronary heart disease is strongly influenced by the fats in the diet. The resulting literature very quickly grew to what one Columbia University pathologist in 1977 described as “unmanageable proportions.” By that time, proponents of Keys’s hypothesis had amassed a body of evidence—a “totality of data,” in the words of the Chicago cardiologist Jeremiah Stamler—that to them appeared unambiguously to support the hypothesis. Actually, those data constituted only half the evidence at best, and the other half did not support the hypothesis. As a result, “two strikingly polar attitudes persist on this subject, with much talk from each and little listening between,” wrote Henry Blackburn, a protégé of Keys at the University of Minnesota, in 1975.
Confusion reigned. “It must still be admitted that the diet-heart relation is an unproved hypothesis that needs much more investigation,” Thomas Dawber, the Boston University physician who founded the famous Framingham Heart Study, wrote in 1978. Two years later, however, he insisted the Framingham Study had provided “overwhelming evidence” that Keys’s hypothesis was correct. “Yet,” he noted, “many physicians and investigators of considerable renown still doubt the validity of the fat hypothesis…. Some even question the relationship of blood cholesterol level to disease.”
Understanding this difference of opinion is crucial to understanding why we all came to believe that dietary fat, or at least saturated fat, causes heart disease. How could a proposition that incited such contention for the first twenty years of its existence become so quickly established as dogma? If two decades’ worth of research was unable to convince half the investigators involved in this controversy of the validity of the dietary-fat/cholesterol hypothesis of heart disease, why did it convince the other half that they were absolutely right?
One answer to this question is that the two sides of the controversy operated with antithetical philosophies. Those skeptical of Keys’s hypothesis tended to take a rigorously scientific attitude. They believed that reliable knowledge about the causes of heart disease could be gained only by meticulous experiments and relentlessly critical assessments of the evidence. Since this was a public-health issue, and any conclusions would have a very real impact on human lives, they believed that living by this scientific philosophy was even more critical than it might be if they were engaged in a more abstract pursuit. And the issue of disease prevention entailed an unprecedented need for the highest standards of scientific rigor. Preventive medicine, as the Canadian epidemiologist David Sackett had observed, targets those of us who believe ourselves to be healthy, only to tell us how we must live in order to remain healthy. It rests on the presumption that any recommendation is based on the “highest level” of evidence that the proposed intervention will do more good than harm.
The proponents of Keys’s hypothesis agreed in principle, but felt they had an obligation to provide their patients with the latest medical wisdom. Though their patients might appear healthy at the moment, they could be inducing heart disease by the way they ate, which meant they should be treated as though they already had heart disease. So these doctors prescribed the diet that they believed was most likely to prevent it. They believed that withholding their medical wisdom from patients might be causing harm. Though Keys, Stamler, and like-minded physicians respected the philosophy of their skeptical peers, they considered it a luxury to wait for “final scientific proof.” Americans were dying from heart disease, so the physicians had to act, making leaps of faith in the process.
This optimistic philosophy was evident early in the controversy. In October 1961, The Wall Street Journal reported that the NIH and the AHA were planning a huge National Diet-Heart Study that would answer the “important question: Can changes in the diet help prevent heart attacks?” Fifty thousand Americans would be fed cholesterol-lowering diets for as long as a decade, and their health compared with that of another fifty thousand individuals who continued to eat typical American diets. This article quoted Cleveland Clinic cardiologist Irving Page saying that the time had come to resolve the conflict: “We must do something,” he said. Jeremiah Stamler said resolving the conflict would “take five to ten years of hard work.” The article then added that the AHA was, nonetheless, assembling a booklet of cholesterol-lowering recipes. The food industry, noted The Wall Street Journal, had already put half a dozen new cholesterol-lowering polyunsaturated margarines on the market. Page was then quoted saying, “Perhaps all this yakking we’ve been doing is beginning to take some effect.” But the yakking, of course, was premature, because the National Diet-Heart Study had yet to be done. In 1964, when the study still hadn’t taken place, a director of the AHA described its purpose as the equivalent of merely “dotting the final i” on the confirmation of Keys’s hypothesis.
This is among the most remarkable aspects of the controversy. Keys and other proponents of his hypothesis would often admit that the benefits of cholesterol-lowering had not been established, but they would imply that it was only a matter of time until they were. “The absence of final, positive proof of a hypothesis is not evidence that the hypothesis is wrong,” Keys would say. This was undeniable—but irrelevant.
The press also played a critical role in shaping the evolution of the dietary-fat controversy by consistently siding with proponents of those who saw dietary fat as an unneccessary evil. These were the researchers who were offering specific, positive advice for the health-conscious reader—eat less fat, live longer. The more zealously stated, the better the copy. All the skeptics could say was that more research was necessary, which wasn’t particularly quotable. A positive feedback loop was created. The press’s favoring of articles that implied Keys’s hypothesis was right helped convince the public; their belief in turn would be used to argue that the time had come to advise cholesterol-lowering diets for everyone, thus further reinforcing the belief that this advice must be scientifically defensible.