Good Calories, Bad Calories

When Keys launched his crusade against heart disease in the late 1940s, most physicians who believed that heart disease was caused by diet implicated dietary cholesterol as the culprit. We ate too much cholesterol-laden food—meat and eggs, mostly—and that, it was said, elevated our blood cholesterol. Keys was the first to discredit this belief publicly, which had required, in any case, ignoring a certain amount of the evidence. In 1937, two Columbia University biochemists, David Rittenberg and Rudolph Schoenheimer, demonstrated that the cholesterol we eat has very little effect on the amount of cholesterol in our blood. When Keys fed men for months at a time on diets either high or low in cholesterol, it made no difference to their cholesterol levels. As a result, Keys insisted that dietary cholesterol had little relevance to heart disease. In this case, most researchers agreed.

In 1951, Keys had an epiphany while attending a conference in Rome on nutrition and disease, which focused exclusively, as Keys later recalled, on malnutrition. There he was told by a physiologist from Naples that heart disease was not a problem in his city. Keys found this comment remarkable, so he and his wife, Margaret, a medical technician whose specialty was fast becoming cholesterol measurements, visited Naples to see for themselves. They concluded that the general population was indeed heart-disease-free—but the rich were not. Margaret took blood-cholesterol readings on several hundred workers and found that they had relatively low cholesterol. They asked “a few questions about their diet,” Keys recalled, and concluded that these workers ate little meat and that this explained the low cholesterol. As for the rich, “I was taken to dine with members of the Rotary Club,” Keys wrote. “The pasta was loaded with meat sauce and everyone added heaps of parmesan cheese. Roast beef was the main course. Dessert was a choice of ice cream or pastry. I persuaded a few of the diners to come for examination, and Margaret found their cholesterol levels were much higher than in the workmen.” Keys found “a similar picture” when he visited Madrid. Rich people had more heart disease than poor people, and rich people ate more fat.

This convinced Keys that the crucial difference between those with heart disease and those without it was the fat in the diet. A few months later, he aired his hypothesis at a nutrition conference in Amsterdam—“fatty diet, raised serum cholesterol, atherosclerosis, myocardial infarction.” Almost no one in the audience, he said, took him seriously. By 1952, Keys was arguing that Americans should reduce their fat consumption by a third, though simultaneously acknowledging that his hypothesis was based more on speculation than on data: “Direct evidence on the effect of the diet on human arteriosclerosis is very little,” he wrote, “and likely to remain so for some time.”

Over the next half-dozen years, Keys assembled a chain of observations that became the bedrock of his belief that fat caused heart disease. He fed high-fat and medium-fat diets to schizophrenic patients at a local mental hospital and reported that the fat content dramatically raised cholesterol. He traveled to South Africa, Sardinia, and Bologna, where Margaret measured cholesterol and they assessed the fat content of the local diet. In Japan, they measured the cholesterol levels of rural fisherman and farmers; they did the same for Japanese immigrants living in Honolulu and Los Angeles. He concluded that the cholesterol/heart-disease association was not peculiar to race or nationality, not a genetic problem, but a dietary one. They visited a remote logging camp in Finland and learned that these hardworking men were plagued by heart disease. A local clinic had six patients, including three young men, who “suffered from myocardial infarction.” They shared a snack with the loggers: “slabs of cheese the size of a slice of bread on which they smeared butter,” Keys wrote; “they washed it down with beer. It was an object lesson for the coronary problem.”

Keys bolstered his hypothesis with a 1950 report from Sweden that heart disease deaths had virtually disappeared there during the German occupation of World War II. Similar phenomena were reported in nations that had undergone severe food-rationing during the war—Finland, Norway, Great Britain, Holland, the Soviet Union. Keys concluded that the dramatic reduction in coronary deaths was caused by decreased consumption of fat from meat, eggs, and dairy products. Skeptics observed, however, that these are among many deprivations and changes that accompany food rationing and occupation. Fewer calories are consumed, for instance, and weight is lost. Unavailability of gasoline leads to increased physical activity. Sugar and refined-flour consumption decreases. Any of these might explain the reduction in heart-disease mortality, these investigators noted.