This is little more than an updated version of the changing-American-diet story Ancel Keys and others had invoked to advocate low-fat diets: we eat fewer carbohydrates and ever more fat then we did in some idealized past, and we pay the price in chronic disease. Keys’s reference point was the American diet circa 1909 (as portrayed by USDA estimates), or the Japanese or Mediterranean diets of the 1950s. When it was suggested to Keys that other nutrition transitions, including those witnessed by Schweitzer and Hutton, could be edifying, he argued that not enough was known about the diets or about the health of those isolated populations for us to draw reliable conclusions. He also insisted that in many of these populations—particularly the Inuit—relatively few individuals were likely to live long enough to develop chronic disease, so little could be learned.

This argument, too, has taken on the aura of undisputed truth. This could be called the “nasty, brutish, and short” caveat, after Thomas Hobbes’s pithy interpretation of the state of primitive lives. But earlier generations of physicians had the advantage of observing conditions of nutrition and health considerably further back on what anthropologists refer to as the curve of modernization. In this sense, their job was easier: noting the absence of a disease in a population, or the appearance of diseases in a previously unaffected population—the transition from healthy populations to sick populations, as Geoffrey Rose would put it—is an observation less confounded with diagnostic and cultural artifacts than are the comparisons of disease rates among populations all of which are afflicted.

Most of these historical observations came from colonial and missionary physicians like Schweitzer and Hutton, administering to populations prior to and coincidental with their first substantial exposure to Western foods. The new diet inevitably included carbohydrate foods that could be transported around the world without spoiling or being devoured by rodents on the way: sugar, molasses, white flour, and white rice. Then diseases of civilization, or Western diseases, would appear: obesity, diabetes mellitus, cardiovascular disease, hypertension and stroke, various forms of cancer, cavities, periodontal disease, appendicitis, peptic ulcers, diverticulitis, gallstones, hemorrhoids, varicose veins, and constipation. When any diseases of civilization appeared, all of them would eventually appear.

This led investigators to propose that all these diseases had a single common cause—the consumption of easily digestible, refined carbohydrates. The hypothesis was rejected in the early 1970s, when it could not be reconciled with Keys’s hypothesis that fat was the problem, an attendant implication of which was that carbohydrates were part of the solution. But was this alternative carbohydrate hypothesis rejected because compelling evidence refuted it, or for reasons considerably less scientific?