Good Calories, Bad Calories

Nonetheless, the numbers were compelling. In 1892, according to William Osler in Principles and Practice of Medicine, only ten diabetics had been diagnosed among the thirty-five thousand patients treated at Johns Hopkins Hospital. At Massachusetts General Hospital in Boston, only 172 patients had been diagnosed as diabetic out of nearly fifty thousand admitted between 1824 and 1898; only eighteen of those were under twenty years old, and only three under ten, suggesting that childhood diabetes was an extremely rare diagnosis. Between 1900 and 1920, according to Haven Emerson, director of the Institute of Public Health at Columbia University, the death rate from diabetes, despite improved treatment of the disease, had increased by as much as 400 percent in American cities. It had increased fifteen-fold since the end of the Civil War. Emerson reported proportional increases in diabetes mortality in Great Britain and France and suggested they were due to the increased consumption of sugar, combined with an increasingly sedentary lifestyle. Moreover, diabetes rates had dropped precipitously during World War I in populations that had faced food shortages or rationing. “It is apparent,” wrote Emerson in 1924, “that rises and falls in the sugar consumption are followed with fair regularity within a few months by similar rises and falls in the death rates from diabetes.”

The hypothesis that sugar and refined carbohydrates were responsible might have survived past the 1930s, but Elliott Joslin refused to believe it, and Joslin’s name was by then “synonymous” with diabetes in the United States. Joslin may once have ranked beneath Frederick Allen in the hierarchy of American diabetologists, but Allen’s reputation had been built on his starvation cure for diabetes, which was only marginally effective, and rendered unnecessary once insulin was discovered in 1921. Joslin achieved lasting fame by pioneering the use of insulin as a treatment. From the 1920s onward, Joslin’s textbook The Treatment of Diabetes Mellitus and his Diabetic Manual were the bibles of diabetology.

When Emerson presented his evidence that rising sugar consumption was the best explanation for the rise in diabetes incidence, Joslin rejected it. He said that increased sugar consumption had been offset in America by decreasing apple consumption, and that the carbohydrates in apples were effectively identical to table sugar as far as diabetics were concerned. (This wasn’t the case, but Joslin had little reason to believe otherwise in the 1920s.) Emerson countered with U.S. Department of Agriculture data reporting an actual increase in apple consumption in the relevant decades, but Joslin was unyielding.

Joslin found it inconceivable that sugar or any other refined starch could have a unique property that other carbohydrates did not. They all broke down to glucose after digestion, or glucose and fructose, in the case of table sugar. The insulin-releasing cells of the pancreas (known as ß cells), which are dysfunctional in diabetes, respond only to the glucose. Early on in his career, Joslin, like Ancel Keys thirty years later, found the Japanese diet to be compelling evidence for the salubrious nature of carbohydrate-rich diets. “A high percentage of carbohydrate in the diet does not appear to predispose to diabetes,” he wrote in 1923, since the Japanese ate such a diet and had an extremely low incidence of diabetes. He acknowledged that the rising death rate from diabetes in the United States coincided with rising sugar consumption, and that diabetes mortality and sugar consumption “must stand in some relation,” but the Japanese experience argued against causality. He considered a rising incidence of obesity to be one factor in the increasing prevalence of diabetes, and decreasing physical activity, caused by the increasing mechanization of American life, to be another. A third factor, as the Japanese experience suggested, was a diet that was fat-rich and carbohydrate-poor.

Joslin effectively based his belief primarily on the work of a single researcher: Harold Himsworth of University College Hospital, London. To Joslin, Himsworth’s “painstakingly accumulated” data constituted compelling evidence that a deficiency of carbohydrates and an excess of fat bring on diabetes. It was Himsworth’s research and Joslin’s faith in it that led a half-century of diabetologists to believe unconditionally that diabetes is not caused by the consumption of sugar and refined carbohydrates.