Good Calories, Bad Calories

All other hormones, however, are secondary to the role of insulin in energy production, utilization, and storage. Historically, physicians have viewed insulin as though it has a single primary function: to remove and store away sugar from the blood after a meal. This is the most conspicuous function impaired in diabetes. But the roles of insulin are many and diverse. It is the primary regulator of fat, carbohydrate, and protein metabolism; it regulates the synthesis of a molecule called glycogen, the form in which glucose is stored in muscle tissue and the liver; it stimulates the synthesis and storage of fats in fat depots and in the liver, and it inhibits the release of that fat. Insulin also stimulates the synthesis of proteins and of molecules involved in the function, repair, and growth of cells, and even of RNA and DNA molecules, as well.

Insulin, in short, is the one hormone that serves to coordinate and regulate everything having to do with the storage and use of nutrients and thus the maintenance of homeostasis and, in a word, life. It’s all these aspects of homeostatic regulatory systems—in particular, carbohydrate and fat metabolism, and kidney and liver functions—that are malfunctioning in the cluster of metabolic abnormalities associated with metabolic syndrome and with the chronic diseases of civilization. As metabolic syndrome implies, and as John Yudkin observed in 1986, both heart disease and diabetes are associated with a host of metabolic and hormonal abnormalities that go far beyond elevations in cholesterol levels and so, presumably, any possible effect of saturated fat in the diet.

This suggests another way to look at Peter Cleave’s saccharine-disease hypothesis, or what I’ll call, for simplicity, the carbohydrate hypothesis of chronic disease. As Cleave pointed out, species need time to adapt fully to changes in their environment—whether shifts in climate, the appearance of new predators, or changes in food supply. The same is true of the internal environment of the human body—Bernard’s milieu intérieur. By far the most dramatic change to this internal environment over the past two million years is due to the introduction of diets high in sugar and refined and other easily digestible carbohydrates. Blood-sugar levels rise dramatically after these meals; insulin levels rise in response and become chronically elevated—hyperinsulinemia—and tissues become resistant to insulin. And because half of every molecule of table sugar (technically known as sucrose) is a molecule of the sugar known as fructose, which is found naturally only in small concentrations in fruits and some root vegetables, the human body has also been confronted with having to adjust to radically large amounts of fructose. In this sense, all of the abnormalities of metabolic syndrome and the accompanying chronic diseases of civilization can be viewed as the dysregulation of homeostasis caused by the repercussions throughout the body of the blood-sugar, insulin, and fructose-induced changes in regulatory systems. (As the geneticist James Neel wrote in 1998 about adult-onset diabetes, “The changing dietary patterns of Western civilization had compromised a complex homeostatic mechanism.”)

It’s possible that obesity, diabetes, heart disease, hypertension, and the other associated diseases of civilization all have independent causes, as the conventional wisdom suggests, but that they serve as risk factors for each other, because once we get one of these diseases we become more susceptible to the others. It’s also possible that refined carbohydrates and sugar, in particular, create such profound disturbances in blood sugar and insulin that they lead to disturbances in mechanisms of homeostatic regulation and growth throughout the entire body.

Any assumptions about regulatory mechanisms and disease, as Claude Bernard explained, have to be understood in the context of the entire harmonic ensemble. “We really must learn, then, that if we break up a living organism by isolating its different parts, it is only for the sake of ease in experimental analysis, and by no means in order to conceive them separately,” Bernard wrote. “Indeed when we wish to ascribe to a physiological quality its value and true significance, we must always refer it to this whole, and draw our final conclusion only in relation to its effects in the whole.” When Hans Krebs paraphrased this lesson a century later, he said that if we neglect “the wholeness of the organism—we may be led, even if we experimented skillfully, to very false ideas and very erroneous deductions.”

Perhaps the simplest example of this kind of erroneous deduction is the common assumption that the cause of high blood pressure and hypertension is excess salt consumption.