The years immediately before and after the discovery of insulin and the introduction of insulin therapy, anything that could prevent diabetic coma for an indefinite period could seem worth the risk. “When I was a student and young doctor” in the 1920s, as the University of Edinburgh diabetologist Derrick Dunlop (later Sir Derrick) described thirty years later, “we were entirely occupied, so far as diabetes was concerned, with endeavoring to keep the patient alive for a while… we were taught little of its ultimate complications, for relatively few patients had by then lived long enough to develop them.”

If an intervention restores the patient to health, but is associated with premature death or disease months or years later from side effects or complications, the treatment might still be readily justified. This was the case with insulin therapy for type 1 diabetes, as it is with many cancer therapies today. But the “ultimate complications” cannot be ignored. If the physician has a choice of two treatments that will restore the patient to health in the short run, then the long-term effects must be weighed before a choice is made.

For a chronic disease or disorder, one like heart disease or type 2 diabetes that disables and kills prematurely but does so only years or decades in the future, physicians had been forced to speculate on whether what they were doing would cause more good than harm. But with the invention of the modern clinical trial in the late 1940s—technically known as a randomized controlled trial—these doctors benefited from one of the great advances in medical science. For the first time, they had a means to assess the long-term risks and benefits of medical interventions and to compare interventions to establish—for an idealized, average patient—what would most likely be the safest, most effective one. The proliferation of clinical trials by the 1980s had launched the era of evidence-based medicine.

With its reliance on clinical trials to dictate accepted practice, medicine left behind the notion of basing therapeutic decisions on clinical experience and observations. But by the time diabetologists started to embrace the notion of an “evidence base” for their beliefs on the nature of a healthy diet, they had already succumbed to the biases formed decades earlier.

*

The history of diabetes therapy, or at least successful therapy, begins with case reports. In an era when a physician might diagnose a case of diabetes only once in his lifetime, John Rollo, a Scottish doctor, saw it three times and published a pamphlet documenting his success in the second of his three cases. “The ingenious author of the work now before us,” as a 1797 review in the Edinburgh journal Annals of Medicine put it, “recommends a mode of treatment, which, in some instances, has been decidedly productive of remarkable benefit. It may justly, therefore, be considered as well meriting a fair trial in future cases.”

Rollo had been trained in Edinburgh, joined the Royal Artillery in 1776, and eventually rose to the rank of surgeon general. He may have been the first physician to successfully bring a case of diabetes under control. Variations on his approach would become the standard of care for the next 125 years.

Until Rollo came along, physicians considered diabetes inevitably a progressive and quickly fatal disease. Their attempts to treat it were scattershot and ineffective; “whatever was available in medicine seems to have been employed against diabetes for centuries,” as one medical historian has put it: “massage in the sun, hot and cold baths, steam baths, wine, whey, milk diet, various nostrums, bleeding, emetics, narcotics, and astringents.”

Rollo had seen his first case of diabetes in 1777, but the patient had been discharged shortly afterward and Rollo learned little from the experience. On October 16, 1796, he diagnosed his second diabetic patient: a Captain Meredith of the Royal Artillery, formerly corpulent, now much diminished in size—“fallen away in fat and flesh considerably,” as Rollo described him. Meredith had experienced symptoms for seven months by the time he saw Rollo, complaining of “great thirst and a keenness of appetite.” He was also urinating copiously, but neither Meredith nor his regular physician had paid attention because he was drinking so much to slake his thirst, “the quantity of urine had appeared to him a necessary consequence.” When Rollo tasted the urine, a common diagnostic method in that era, it was noticeably sweet, confirming that his patient had diabetes.

Rollo theorized that the cause of the disease was the formation of carbohydrates in the stomach—an excess of “saccharine matter.” Assuming that the substance could only come from vegetable foods, he concluded that they should be restricted. He therefore prescribed an “animal diet” (and various salves and concoctions, including opium) as a treatment for Meredith. His patient was expected to eat puddings “made of blood and suet only” for lunch, and old meats and fat “as rancid as can be eaten” for dinner. He was allowed milk for breakfast and lunch, and bread and butter, so his diet was not free of vegetable foods, though nearly so.

The diet rendered Meredith’s urine sugar-free and returned him to health. Within a month, Rollo had prohibited Meredith from drinking the milk (which contains carbohydrates in the form of lactose, although Rollo would not have known that) and replaced it with what he called beef tea—we would call it broth or stock—made from boiling fat beef (or mutton) with water, and then straining the result to produce a clear liquid.

By the end of the year, Meredith seemed “free of disease,” wrote Rollo, “rapidly gaining flesh,” and was allowed to eat more bread and to exercise. By the following March, Meredith seemed cured. He “might, we apprehend, now eat and drink any thing with impunity,” Rollo noted. On May 10 of the following year, Meredith wrote to Rollo that he continued “in perfect health.” (Historians later established that Meredith remained, as his wife would write to a relative in 1805, “in tolerable health but quite thin.” He died in March 1809, twelve years after last consulting with Rollo.)

Rollo’s third case didn’t go as well, but confirmed, Rollo thought, the principles of the animal diet. The patient was a fifty-seven-year-old general in the British army who had been ill for at least three years. Rollo first saw him in January 1797 and was not optimistic that he could return him to health. “We are satisfied the saccharine matter and morbid action of the stomach may be removed, yet the sequela of the disease may be such as to prevent the return of perfect health.” He reported, once again, that so long as his patient adhered strictly to the animal diet, his condition improved. By now Rollo’s dietary prescription was less reliant on rancid old meat and fat, and allowed meat of any kind.

Whenever the general’s health deteriorated, Rollo would interrogate his patient and conclude that he had been eating vegetable matter or fruit or drinking beer. “We have on the whole to lament our patient’s inclination to variety,” Rollo wrote, “and his extreme impatience under restrictions, as otherwise we have no doubt he would have returned in a much better state to his family.” When the general returned home, already cheating on the animal diet, a local physician further encouraged him “to eat what he pleased, and to drink wine,” Rollo reported, and the general did. He was soon dead.

Rollo then compiled the two case studies and his speculations into a pamphlet and posted it: he wrote, “to every person in England or Scotland, who I thought were likely to meet with the disease; and I solicited a trial of the mode of cure, with an account of the results.” Physicians were encouraged to write back to him with their experience, and some two dozen did. He compiled those into a book with his two cases and published it in multiple editions. The conclusion, again, was that the animal diet worked. Removing the vegetable matter from the diet resulted in mostly sugar-free urine, a resolution of the thirst, and normalizing of the appetite and urination. The patients felt healthier.

The letters to Rollo also confirmed that the animal diet was seen by patients, and often their physicians, as only a short-term necessity. The patients would ease off the dietary restrictions as soon as they started experiencing beneficial results. Rollo, for his part, was confident the diet would work if the patient would follow it. “We have to lament, that our mode of cure is so contrary to the inclinations of the sick,” Rollo wrote. “Though perfectly aware of the efficacy of the regimen, and the impropriety of deviations, yet they commonly trespass, concealing what they feel as a transgression on themselves. They express a regret, that a medicine could not be discovered, however nauseous, or distasteful, which would supersede the necessity for any restriction in diet.”

Rollo hoped, as did the other physicians trying his approach, that once the disease was in abeyance, it was cured, or maybe it could be cured. Building up the body’s ability to tolerate carbohydrates— vegetable matter—seemed to be the obvious therapeutic goal: establish a maximum amount of carbohydrates the patient could tolerate without the symptoms reappearing. Rollo recommended that when the patient seemed to be well, the physician should suggest “a gradual return to the use of bread, and those vegetables and drinks which are the least likely to furnish saccharine matter, or to become acid in the stomach.” He also worried about causing “scurvy,* or something akin to it” without any vegetables in the diet.

It all came down to a balancing act between physician and patients, between the strict animal diet that might keep the disease at bay and what the patients preferred to eat and the physicians thought they should. This conflict was most apparent with children, which is still the case today. One physician in the London area wrote to Rollo in February 1798 describing his trial of Rollo’s animal diet with a twelve-year-old girl. She was “of a thin habit of body, tall of her age,” he wrote, accustomed “to eat much fruit, sweetmeats and pickles,” and now afflicted by diabetes. As her health would seemingly improve on the animal diet, the physician would either give her a “small quantity of bread” or a few biscuits to see if the sweet urine returned. Occasionally the physician would learn that his young patient had been indulging herself in forbidden foods. Thirst, headache, and sweet urine betrayed the deviation. In his letter to Rollo, the physician notes repeated transgressions followed, invariably, by assurances from the young patient of “more steadiness in future.” If nothing else, the physician concludes, Rollo has gifted medicine with a way to control diabetes. After that, it was up to the patient.

__________________________________

Excerpted from Rethinking Diabetes: What Science Reveals About Diet, Insulin, and Successful Treatments by Gary Taubes. Copyright © 2024. Published by Alfred A. Knopf, an imprint of Knopf Doubleday Publishing Group, a division of Penguin Random House, LLC.