Cleave would later be disparaged for suggesting that all chronic diseases of civilization have a single primary cause, but he insisted that it was naive to think otherwise. Though it may seem odd, he considered dental cavities the chronic-disease equivalent of the canary in the mine. If cavities are caused primarily by eating sugar and white flour, and cavities appear first in a population no longer eating its traditional diet, followed by obesity, diabetes, and heart disease, then the assumption, until proved otherwise, should be that the other diseases were also caused by these carbohydrates.
Diabetes, obesity, coronary heart disease, gallstones and gall-bladder disease, and cavities and periodontal disease are intimately linked. As early as 1929, physicians were reporting that a fourth of their coronary-heart- disease patients also had diabetes. Diabetics, as Joslin noted, were especially prone to atherosclerosis, which became increasingly clear after the discovery of insulin. Studies in the late 1940s revealed that diabetic men were twice as likely to die of heart disease as nondiabetics; diabetic women were three times more likely. Moreover, diabetics had an exceptionally high rate of gallstones; and the obese had an exceptionally high rate of gall-bladder disease. As Joslin’s textbook also observed, “The destruction of teeth and the supporting structures is very active just prior to the onset of diabetes,” connecting cavities to the disease.
Cleave’s desire for simplicity led him to theorize that any cluster of diseases so intimately associated must have a single underlying cause. Darwin’s theory of evolution led Cleave to believe that endemic chronic disease must be caused by a relatively rapid change in our environment to which we had not yet adapted. He called this idea “The Law of Adaptation”: species require “an adequate period of
Cleave believed the concentration of carbohydrates in the refining process did its damage in three ways.
First, it led to overconsumption, because of what he called the deception of the appetite-control apparatus by the density of the carbohydrates. He contrasted the “eating of a small quantity of sugar, say roughly a teaspoonful,” with the same quantity in its original form—a single apple, for instance. “A person can take down teaspoonfuls of sugar fast enough, whether in tea or any other vehicle, but he will soon slow up on the equivalent number of apples…. The argument can be extended to contrasting the 5 oz. of sugar consumed, on the average, per head per day in [the United Kingdom] with up to a score of average-sized apples…. Who would consume that quantity daily of the natural food? Or if he did, what else would he be eating?”
Second, this would be exacerbated by the removal of protein from the original product. Cleave believed (incorrectly) that peptic ulcers were caused by the lack of protein necessary to buffer the gastric acid in the stomach.
Finally, the refining process increased the rate of digestion of carbohydrates, and so the onrush of blood sugar on the pancreas, which would explain diabetes. “Assume that what strains the pancreas is what strains any other piece of apparatus,” wrote Cleave and Campbell, “not so much the total amount of work it is called upon to do, but the rate at which it is called upon to do it. In the case of eating potatoes, for example, the conversion of the starch into sugar, and the absorption of this sugar into the blood-stream, is a slower and gentler process than the violent one that follows the eating of [any] mass of concentrated sugar.”
The link between refined carbohydrates and disease had been obscured over the years, Cleave and Campbell explained, by the “insufficient appreciation of the distinction” between carbohydrate foods in their natural state and the unnatural refined carbohydrates—treating sugar and white flour as equivalent to raw fruit, vegetables, and wholemeal flour. When researchers looked at trends between diet and disease, as Himsworth and Joslin had done with diabetes and Keys and a later generation of researchers would do with heart disease and even cancer, they would measure only fat, protein, and total carbohydrate consumption and fail to account for any potential effect of refined carbohydrates. Occasionally, they might include sugar consumption in their analyses, but they would rarely make a distinction between wholemeal bread and white flour, between brown rice and white. In most cases, cereal grains, tubers, vegetables, and fruits, and white sugar, flour, rice, and beer, were all included under the single category of carbohydrate. “While the consumption of all carbohydrates may not be moving appreciably with the rise or fall in the incidence of a condition,” Cleave and Campbell explained, “the consumption of the refined carbohydrates may be moving decisively.”
Cleave first made this point in 1956, when he published his hypothesis in an article that also contested Joslin’s belief that the increased incidence of diabetes in the twentieth century was unrelated to sugar consumption. Had Joslin or Himsworth charted sugar consumption separately from that of all carbohydrates, Cleave wrote, “what was the opposite of a relationship between diabetes mortality and carbohydrate consumption would become a very close relationship.”*33 (See chart on following page.)
Cleave had identified one of the fundamental flaws of modern nutrition and chronic-disease epidemiology. Greater affluence inevitably takes populations through a nutrition transition that represents a congruence of fundamental changes in diet. Meat consumption tends to increase, and so saturated fat increases as well. Grain consumption decreases, and so carbohydrate consumption as a whole decreases. But the carbohydrates consumed are more highly refined: white rice replaces brown, white flour replaces wholemeal; sugared beverages and candy spark a dramatic increase in sugar consumption. As a result, whenever investigators tested the hypothesis that chronic disease was caused by high fat intake or even high animal-fat intake or low carbohydrate intake, the refinement of the carbohydrates would
Despite the century of debate in the United Kingdom on the merits of white flour and wholemeal flour and the potential evils of sugar, it wouldn’t be until the 1990s that epidemiologists began to delineate between refined and unrefined carbohydrates in their dietary analyses. Even in 1989, when the National Academy of Sciences published its seven-hundred-page
When Keys linked the low-fat, high-carbohydrate diet of the Japanese in the late 1950s to the extremely low incidence of heart disease, he paid no attention to sugar consumption. Fat consumption in Japan was extremely low, as were heart-disease rates, and so he concluded that the lower the fat the better. But the consumption of sugars in Japan was very low, too—less than forty pounds per person per year in 1963, and still under fifty pounds
