Good Calories, Bad Calories

they were to be consistent with Keys’s hypothesis. Fiber, the indigestible carbohydrates in vegetables, starches, and grains, now replaced refined carbohydrates and sugar in the debate about the nutritional causes of chronic diseases. The fiber hypothesis captured the public’s nutritional consciousness by virtue of the messianic efforts of a single investigator, a former missionary surgeon named Denis Burkitt, who proposed that this indigestible roughage was a requisite component of a healthy diet. The notion was consistent with Keys’s hypothesis, which was not the case with Cleave’s or Yudkin’s hypothesis, and it resonated also with the era’s countercultural leanings toward diets heavy in vegetables, legumes, and cereal grains.

Burkitt’s fiber hypothesis was based originally and in its entirety on Cleave’s saccharine-disease hypothesis, but simply inverted the causal agent. Rather than proclaim, as Cleave did, that chronic disease was caused by the addition of sugar and refined carbohydrates to diets that we had evolved naturally to eat, Burkitt laid the blame on the subtraction of the fiber from those evolutionarily ideal diets, which in turn led to constipation and then, through a variety of mechanisms, all the chronic diseases of civilization. The fiber deficiency itself was caused either by the removal of fiber during the refining of carbohydrates or by the consumption of refined carbohydrates in lieu of the fibrous, bulky roughage we should be eating. The fiber hypothesis and the refined-carbohydrate hypothesis of chronic disease were photographic negatives of each other, and yet the fiber hypothesis caught on immediately upon appearing in the journals. The refined-carbohydrate hypothesis, which was the only one of the two that was capable of explaining the actual evidence, remained a fringe concept.

Denis Burkitt began his career as a missionary surgeon in Uganda in 1947. In the early 1960s, he earned his renown—“one of the world’s best-known medical detectives,” as the Washington Post would call him—for his studies of a fatal childhood cancer that came to be known as Burkitt’s lymphoma and would be the first human cancer ever linked to a viral cause. That discovery alerted Burkitt to the lessons to be learned by tracking the geographical distribution of disease. Burkitt spent five years gathering information about the lymphoma from hundreds of African hospitals, and made a legendary ten-thousand-mile, sixty-hospital trek from Kampala to Johannesburg and back as part of his research.

In 1966, Burkitt returned to England, where he worked as a cancer epidemiologist for the Medical Research Council. There Richard Doll told him about Cleave and his saccharine-disease hypothesis. Burkitt met with Cleave and read Diabetes, Coronary Thrombosis and the Saccharine Disease, which he found revelatory. Cleave possessed “perceptive genius, persuasive argument and irrefutable logic,” Burkitt wrote.

What he was saying was that many of the common diseases in post-industrialized western countries are rare throughout the third world, were rare even in England or New York until about the First World War, are equally common in black and white Americans, and therefore must be due not to our skin color or our genes, but to the way we live. Now, this made an enormous amount of sense to me because I knew from my experience in Africa that he was perfectly right saying this.

On a tour of the United States, Burkitt visited hospitals and observed, as George Campbell had a decade earlier, that African-American patients in these hospitals were often obese, diabetic, or atherosclerotic, conditions virtually nonexistent among the black Ugandans Burkitt had treated.

Burkitt considered himself in the ideal position to test Cleave’s hypothesis on a wider scale. He had already established a network of 150 African hospitals, mostly missionary hospitals in rural areas, that mailed him monthly reports on their cancer cases: “I was able to ask them all: ‘Do you see gallstones, appendicitis, diverticular disease, coronary heart disease….’” Burkitt also sent his questionnaire to mission hospitals through out the world, and over eight hundred faithfully returned them. The results confirmed the basics of Cleave’s hypothesis. Whereas Cleave had anecdotal evidence, Burkitt recalled, he now had “anecdotal multiplied by a thousand,” and it was all consistent. Moreover, he had the necessary reputation to be taken seriously, whereas Cleave did not. Cleave, Campbell, and others had been “written off as cranks,” Burkitt said. “Now, just because there happened to be a Burkitt’s lymphoma, when Burkitt said, ‘What about looking at this,’ people listened to me when they hadn’t listened to far better guys.”

Through the early 1970s, Burkitt published a series of articles expanding on Cleave’s hypothesis. “These ‘western’ diseases are certainly associated geographically and in many instances tend to be related to one another in individual patients,” Burkitt wrote in the Journal of the National Cancer Institute in 1971. “My epidemiological studies in Africa and elsewhere substantiate Cleave’s basic hypothesis. Changes made in carbohydrate food may of course be only one of many etiological factors, but in some instances they would appear to be the major one.”

But Burkitt was beginning to revise Cleave’s hypothesis. Now Burkitt’s working assumption, as he explained in the JNCI, was that any dietary factors responsible for benign conditions such as appendicitis or diverticulitis were likely to be responsible as well for related malignant conditions—in particular, colon and rectal cancer. Burkitt’s research had led him to Thomas Allinson, who in the 1880s argued that white flour caused constipation, hemorrhoids, and other ills of modern societies. It also led him to a 1920 article by the Bristol University surgeon Arthur Rendle Short, documenting a dramatic increase in the incidence of appendicitis that Rendle Short also blamed on white flour and the lack of fiber in modern diets. Burkitt believed he could draw a direct line of causation from the absence of fiber in refined carbohydrates to constipation, hemorrhoids, appendicitis, diverticulitis, polyps, and finally malignant colon and rectal cancer.

Burkitt’s African correspondents had reported that appendicitis increased dramatically in urban populations—at Burkitt’s Mulago Hospital in Kampala, the number of yearly appendectomies had increased twenty-fold from 1952 to 1969—whereas polyps, diverticular disease, and colorectal cancer, all common in the United States and Europe, wrote Burkitt, were still “very rare in Africa and almost unknown in rural communities.” Burkitt concluded that appendicitis, just as it appeared in Western nations typically in children, appeared in Africans, both adults and children, within a few years of the adoption of Western diets.

Burkitt focused now on constipation. He theorized that removing the fiber from cereal grains would slow the “transit time” of the stool through the colon. Not only would any carcinogens in the stool therefore have more time to inflict damage on the surrounding cells, but it was conceivable that the overconsumption of refined carbohydrates would increase the bacterial flora of the stool, and that in turn could lead to carcinogens being metabolized by the bacteria out of “normal bowel constituents.” Burkitt could offer no explanation for why this might cause appendicitis, but he was confident that some combination of all these factors played a role.

In the summer of 1969, Burkitt began studying stool characteristics in available subjects. “Finished bowel transit tests on family,” he recorded in his diary on July 4. The following month, he visited Alec Walker, who ran the human biology department at the South African Institute of Medical Research. Walker had been studying the rising tide of chronic diseases in urban Bantus in South Africa since the late 1940s, and he was the rare investigator who shared with Burkitt an interest in human feces and constipation. Walker had done extensive studies linking the relative lack of constipation among black convicts in the local prison, as well as the lack of appendicitis in the Bantus at large, to their traditional high-fiber diets. (Walker publicly dismissed the hypothesis that sugar or refined carbohydrates caused heart disease, but he also reported that the Bantus developed chronic disease only after they moved into the city and began consuming “more white bread, sugar, soft drinks and European liquor.”) Walker had also just submitted an article to the British Medical Journal linking the very low mortality rates from colon cancer among the Bantus to their bowel motility, a characteristic, he wrote, that was “largely lost” among Western societies. Walker’s research gave Burkitt the confidence to devote his efforts to the study of stool characteristics and bowel behavior, hoping to associate in a scientific manner fiber deficiency, constipation, and the presence of chronic diseases.

It was precisely this work that led to the fiber hypothesis and its present place in our nutritional consciousness.