Good Calories, Bad Calories

Five days after Kolata’s article on the negative results from the Phoenix and NCI trials, the Times published an explanatory article by Kolata—“Health Advice: A Matter of Cause, Effect and Confusion”—in which she discussed why the public had come to be misled on the benefits of fiber. She suggested that one reason was the loose use of language: “Scientists and the public alike use words like ‘prevents’ and ‘protects against’ and ‘lowers the risk of’ when they are discussing evidence that is suggestive, and hypothesis-generating, as well as when they are discussing evidence that is as firm as science can make it.” Burkitt’s fiber hypothesis, she said, had been based on hypothesis-generating data—international comparisons, in particular—and had then been refuted by the best studies science could do. “Yet even in the aftermath of the high-fiber diet studies,” Kolata noted, “researchers were speaking confidently about other measures people could take to ‘prevent’ colon cancer, like exercising and staying thin. And they were saying that there were reasons to keep eating fiber because it could ‘reduce the risk’ of heart disease. When asked about the evidence for these statements, the researchers confessed that it was, of course, the lower level hypothesis-generating kind.”

The very next day, the Times ran an article by Burros entitled “Plenty of Reasons to Say, ‘Please Pass the Fiber,’” in which she suggested, based on what Kolata would have called “hypothesis-generating data,” that eating fiber “significantly” lowers the risk of heart attack in women, and that “fiber is also useful in preventing the development of diabetes,” “helps control obesity,” and “may also be useful in reducing hypertension.” Less than a month later, Brody followed with an article entitled “Vindication for the Maligned Fiber Diet,” noting that, although fiber had “been knocked around a bit lately, after three disappointing studies failed to find that a high-fiber diet helped to prevent colon cancer,” a recent study published in the New England Journal of Medicine of thirteen subjects followed for six weeks suggested it helped them to better control their diabetes and so should be eaten on that basis. “Since diabetes greatly increases a person’s risk of developing heart disease and other disorders caused by fat-clogged arteries,” Brody wrote, “the results of this study are highly significant to the 14 million Americans with Type 2 diabetes.” By 2004, Brody was advocating high-fiber diets solely for their alleged ability, untested, to induce long-term weight loss and weight maintenance. In effect, fiber had now detached itself from its original hypothesis and existed in a realm always a step beyond what had been tested. Cleave’s hypothesis that refined carbohydrates and sugars were the problem, the single best explanation for the original data, had been forgotten entirely.

Chapter Eight

THE SCIENCE OF THE CARBOHYDRATE HYPOTHESIS

Forming hypotheses is one of the most precious faculties of the human mind and is necessary for the development of science. Sometimes, however, hypotheses grow like weeds and lead to confusion instead of clarification. Then one has to clear the field, so that the operational concepts can grow and function. Concepts should relate as directly as possible to observation and measurements, and be distorted as little as possible by explanatory elements.

MAX KLEIBER, The Fire of Life:

An Introduction to Animal Energetics, 1961

AFTER THE UNITED STATES EXPLORATION EXPEDITION under Captain Charles Wilkes visited the Polynesian atolls of Tokelau in January 1841, the expedition’s scientists reported finding no evidence of cultivation on the atolls, and confessed their surprise that the islanders could thrive on a diet composed primarily of coconuts and fish. Tokelau came under the administration of New Zealand in the mid-1920s, but the atolls remained isolated, visited only by occasional trading ships from Samoa, three hundred miles to the north. As a result, Tokelau lingered on the fringes of Western influence. The staples of the diet remained coconuts, fish, and a starchy melon known as breadfruit (introduced in the late nineteenth century) well into the 1970s. More than 70 percent of the calories in the Tokelau diet came from coconut; more than 50 percent came from fat, and 90 percent of that was saturated.