The vitamin-C molecule is similar in configuration to glucose and other sugars in the body. It is shuttled from the bloodstream into the cells by the same insulin-dependent transport system used by glucose. Glucose and vitamin C compete in this cellular-uptake process, like strangers trying to flag down the same taxicab simultaneously. Because glucose is greatly favored in the contest, the uptake of vitamin C by cells is “globally inhibited” when blood-sugar levels are elevated. In effect, glucose regulates how much vitamin C is taken up by the cells, according to the University of Massachusetts nutritionist John Cunningham. If we increase blood-sugar levels, the cellular uptake of vitamin C will drop accordingly. Glucose also impairs the reabsorption of vitamin C by the kidney, and so, the higher the blood sugar, the more vitamin C will be lost in the urine. Infusing insulin into experimental subjects has been shown to cause a “marked fall” in vitamin-C levels in the circulation.

In other words, there is significant reason to believe that the key factor determining the level of vitamin C in our cells and tissues is not how much or little we happen to be consuming in our diet, but whether the starches and refined carbohydrates in our diet serve to flush vitamin C out of our system, while simultaneously inhibiting the use of what vitamin C we do have. We might get scurvy because we don’t faithfully eat our fruits and vegetables, but it’s not the absence of fruits and vegetables that causes the scurvy; it’s the presence of the refined carbohydrates.*96 This hypothesis has not been proven, but, as Will and Byers suggested, it is both biologically plausible and empirically evident.

When we discuss the long-term effects of diets that might reverse or prevent obesity, we must not let our preconceptions about the nature of a healthy diet bias the science and the interpretation of the evidence itself.

Chapter 20

Chapter Twenty

UNCONVENTIONAL DIETS

Here was a treatment, that, in its encouragement to eat plentifully, to the full satisfaction of the appetite, seemed to oppose not only the prevailing theory of obesity but, in addition, principles basic to the biological sciences and other sciences as well. It produced a sense of puzzlement that was a mighty stimulant to thought on the matter.

ALFRED PENNINGTON, talking about a high-fat, high-protein diet, unrestricted in calories, in the American Journal of Digestive Diseases, 1954

Does it help people lose weight? Of course it does. If you cannot eat bread, bagels, cake, cookies, ice cream, candy, crackers, muffins, sugary soft drinks, pasta, rice, most fruits and many vegetables, you will almost certainly consume fewer calories. Any diet will result in weight loss if it eliminates calories that previously were overconsumed.

JANE BRODY, talking about a high-fat, high-protein diet, unrestricted in calories, in the New York Times, 2002