Good Calories, Bad Calories (14 page)

The fol owing December, the National Institutes of Health hosted a “consensus conference” and effectively put an end to thirty years of debate. Ideal y, in a consensus conference an unbiased expert panel listens to testimony and arrives at conclusions on which everyone agrees. In this case, Rifkind chaired the planning committee, of which Steinberg was a member. Steinberg was then chosen to head the expert panel that would draft the consensus. The twenty speakers did include three skeptics—Ahrens, Robert Olson, and Michael Oliver, a cardiologist with the Medical Research Council in London—who argued that the wisdom of a cholesterol-lowering diet could not be established on the strength of a drug experiment, let alone one with such borderline results. A month after the conference, the NHLBI epidemiologist Salim Yusuf described the controversy to Science as remaining as polarized as ever:

“Many people have already made up their minds that cholesterol-lowering helps, and they don’t need any evidence. Many others have decided that cholesterol-lowering is not helpful, and they don’t need any evidence either.”

March 1984: the results of a drug trial are translated into the message that fatty foods will cause heart disease. (Time magazine © 1984 Time Inc. Reprinted by permission.)

But this was not the message of Steinberg’s “consensus” panel, which was composed exclusively of lay experts and clinical investigators who “were selected to include only [those] who would, predictably, say that al levels of blood cholesterol in the United States are too high and should be lowered,” as Oliver wrote in a Lancet editorial fol owing the conference. “And, of course, this is exactly what was said.” Indeed, the consensus conference report, written by Steinberg and his panel, revealed no evidence of any discord or dissent. There was “no doubt,” it concluded, that low-fat diets “wil afford significant protection against coronary heart disease” to every American over the age of two. The NIH Consensus Conference official y gave the appearance of unanimity where no unanimity existed. After al , if there had been a true consensus, as Steinberg himself later explained, “you wouldn’t have had to have a consensus conference.”

THE GREATER GOOD

In reality, those who repudiate a theory that they had once proposed, or a theory that they had accepted enthusiastical y and with which they had identified themselves, are very rare. The great majority of them shut their ears so as not to hear the crying facts, and shut their eyes so as not to see the glaring facts, in order to remain faithful to their theories in spite of al and everything.

MAURICE ARTHUS, Philosophy of Scientific Investigation, 1921

ONCE THE NATIONAL INSTITUTES OF HEALTH had declared the existence of a consensus, the controversy over dietary fat appeared to be over. A series of official government reports and guidelines that fol owed served to confirm it. In 1986, the NIH established the National Cholesterol Education Program (NCEP), which released its first guidelines for cholesterol reduction in October 1987. “The edict has been handed down,” as the Washington Post reported: “total blood cholesterol should be below 200…. If it’s above that threshold physicians must put their patients on cholesterol-lowering diets or use some of the new cholesterol-combating drugs to bring down the levels.” Surgeon General C. Everett Koop’s seven-hundred-page Report on Nutrition and Health, released in July 1988, “exhorts Americans to cut out the fat,” Time reported. The “disproportionate consumption of food high in fats,”

according to the Report on Nutrition and Health, could be held responsible for two-thirds of the 2.1 mil ion deaths in the United States in 1988. “The depth of the science base…is even more impressive than that for tobacco and health in 1964,” explained Koop in the introduction, which was certainly not the case. In March 1989, the National Academy of Sciences released its version of the surgeon general’s report, thirteen hundred pages long, entitled Diet and Health: Implications for Reducing Chronic Disease Risk. “Highest priority is given to reducing fat intake,” the NAS report stated, “because the scientific evidence concerning dietary fats and other lipids and human health is strongest and the likely impact on public health the greatest.”

These authoritative reports implied without foundation that yet more independent expert committees had weighed the evidence and agreed that dietary fat was a kil er. But the surgeon general’s report had been overseen by J. Michael McGinnis, who had been Mark Hegsted’s liaison at the Surgeon General’s Office when the first USDA Dietary Guidelines had been drafted a decade earlier. The chapter linking dietary fat to heart disease had been contracted out to the same administrators at the National Heart, Lung, and Blood Institute who had organized the NIH Consensus Conference and founded the National Cholesterol Education Program. In Diet and Health, the chapter assessing the hazards of fat had been drafted by three old hands in the dietary-fat controversy: Henry Blackburn, a protégé of Ancel Keys at Minnesota; Richard Shekel e, who had co-authored more than forty papers with Jeremiah Stamler; and DeWitt Goodman, who had chaired the National Cholesterol Education Program panel that had drafted the 1987 guidelines.*18

In the media coverage that fol owed, those investigators skeptical of the underlying science seemed to have vanished from the public debate. New on the scene were public-interest groups—most notably, the Center for Science in the Public Interest and its director, Michael Jacobson—arguing that neither the NAS nor the surgeon general had gone far enough in pushing a national low-fat diet plan. Both the Washington Post and the New York Times quoted Jacobson scolding the authors of Diet and Health for lacking “the courage” to tel Americans straight out that a healthy lifestyle required much

“greater reductions” in total fat, saturated fat, and cholesterol. In the Post article, Arno Motulsky, chairman of the NAS committee that compiled the report, acknowledged that one intention of Diet and Health was to convince Americans further of the existence of a scientific consensus on the benefits of reducing fat in the diet. “Many people may be confused by the vast amount of advice about what to eat,” he said. “Some may have delayed making changes in their diets until they are more convinced that scientists have reached consensus. We hope our report wil help these individuals move from inaction and complacency to action.” The public face of the controversy had now shifted entirely. It was no longer about the validity of the underlying science, which was no less ambiguous than ever, but about whether Americans should be eating low-fat diets or very low-fat diets.

One striking fact about this evolution is that the low-fat diets now being recommended for the entire nation had only been tested twice, as I’ve said, once in Hungary and once in Britain, and in only a few hundred middle-aged men who had already suffered heart attacks. The results of those trials had been contradictory. The diets tested since then had been exclusively cholesterol-lowering diets that replaced saturated fats with unsaturated fats.

The rationale for lowering the total fat content of the diet to 30 percent was the tangential expectation that such a diet would help us control our weight. In 1984, the year of the NIH Consensus Conference, Robert Levy and Nancy Ernst of the NHLBI had described the state of the science this way: “There has been some indication that a low-fat diet decreases blood cholesterol levels,” they wrote. “There is no conclusive proof that this lowering is independent of other concomitant changes in the diet (for example, increased dietary fiber or complex carbohydrate…or decreased cholesterol or saturated fatty acid level)…. It may be said with certainty, however, that because 1 g fat provides about 9 calories—compared to about 4 calories for 1 g of protein or carbohydrate—fat is a major source of calories in the American diet. Attempts to lose weight or maintain weight must obviously focus on the content of fat in the diet.” Though this was an untested conjecture (however obvious it might seem), the official healthy diet of the nation was now a low-fat diet. A new generation of diet doctors, the most influential of whom was Dean Ornish, were even prescribing 10-percent-fat diets, if not lower.

Another striking aspect of the low-fat diet recommendations is how little any individual might benefit from lowering his cholesterol.*19 Keys and others had argued that heart disease had to be prevented because its first symptom was often a fatal heart attack. But in twenty-four years of observation, the Framingham Heart Study had detected no relationship between cholesterol and sudden cardiac death. The likelihood of suffering a fatal first heart attack was no less for those with a cholesterol level of 180 mg/dl than for those with 250. “The lack of association between serum cholesterol level and the incidence of sudden death suggests that factors other than the atherosclerotic process may be of major importance in this manifestation of coronary artery disease,” explained Thomas Dawber.

There is also little to gain from lowering cholesterol even in less catastrophic manifestations of the disease. This was made clear in 1986, when Stamler published a reanalysis of his MRFIT data in JAMA. As Stamler reported it, the MRFIT investigators had continued to track the health of the 362,000 middle-aged men who had original y been screened as potential candidates for MRFIT, including death certificates. Stamler reported that the cholesterol/heart-disease association applied at any level of cholesterol, and so anyone would benefit from lowering cholesterol.

Using the MRFIT data, however, it is possible to see how large or smal that benefit might be (see chart, below). For every one thousand middle-aged

men who had high cholesterol—between, say, 240 and 250 mg/dl—eight could expect to die of heart disease over any six-year period. For every thousand men with cholesterol between 210 and 220, roughly six could expect to die of heart disease. These numbers suggest that reducing cholesterol from, say, 250 to 220 would reduce the risk of dying from a heart attack in any six-year period from .8 percent (eight in a thousand) to .6 percent (six in a thousand). If we were to stick rigorously to a cholesterol-lowering diet for thirty years—say, from age forty to seventy, at which point high cholesterol is no longer associated with an increased risk of heart disease—we would reduce our risk of dying of a heart attack by 1 percent.

The data from the MRFIT trial showing the relationship between heart-disease mortality and cholesterol levels in the blood.

The data from the MRFIT trial showing the relationship between total mortality—i.e., death by all causes—and cholesterol levels in the blood.

Whether we would actual y live longer by lowering our cholesterol is, of course, a different question. People die from myriad causes. Though Stamler neglected to include total mortality data in his JAMA article, a second group of MRFIT investigators did include it in an article published in The Lancet just a month earlier.

Their data revealed that for every thousand men with cholesterol around 240 to 250 mg/dl, twenty to twenty-three would likely die of any cause within six years. For those whose cholesterol was approximately 220, between nineteen and twenty-one were likely to die. In other words, for every thousand middle-aged men who successful y lower their cholesterol by diet from, say, 250 to 220, at most four (although perhaps none) can expect to avoid death during any six-year period. Nineteen or twenty of these men can expect to die whether they diet or not. For the remaining 98 percent, they wil live regardless of their choice. Moreover, lowering cholesterol further would not help. The death rate for men whose cholesterol is below 200 appears little different from that of men whose cholesterol fal s between 200 and 250. Only for those men whose cholesterol is above 250 mg/dl does it appear that lowering cholesterol might improve the chances of living longer.