That sugar is half fructose is what fundamentally differentiates it from starches and even the whitest, most refined flour. If John Yudkin was right that sugar is the primary nutritional evil in the diet, it would be the fructose that endows it with that singular distinction. With an eye toward primitive diets transformed by civilization, and the change in Western diets over the past few hundred years, it can be said that the single most profound change, even more than the refinement of carbohydrates, is the dramatic increase in fructose consumption that comes with either the addition of fructose to a diet lacking carbohydrates, or the replacement of a large part of the glucose from starches by the fructose in sugar.

Because fructose barely registers in the glycemic index, it appeared to be the ideal sweetener for diabetics; sucrose itself, with the possible exception of its effect on cavities, appeared no more harmful to nondiabetics, and perhaps even less so, than starches such as potatoes that were being advocated as healthy substitutes for fat in the diet. In 1983, the University of Minnesota diabetologist John Bantle reported in The New England Journal of Medicine that fructose could be considered the healthiest carbohydrate. “We see no reason for diabetics to be denied foods containing sucrose,” Bantle wrote. This became the official government position. The American Diabetes Association still suggests that diabetics need not restrict “sucrose or sucrose-containing foods” and can even substitute them, if desired, “for other carbohydrates in the meal plan.”

In 1986, the FDA exonerated sugar of any nutritional crimes on the basis that “no conclusive evidence demonstrates a hazard.” The two-hundred-page report constituted a review of hundreds of articles on the health aspects of sugar, many of which reported that sugar had a range of potentially adverse metabolic effects related to a higher risk of heart disease and diabetes. The FDA interpreted the evidence as inconclusive. Health reporters, the sugar industry, and public-health authorities therefore perceived the FDA report as absolving sugar of having any deleterious effects on our health.

The identical message was passed along in the 1988 Surgeon General’s Report on Nutrition and Health and the 1989 National Academy of Sciences Diet and Health report. Here, too, the inconclusive studies and ambiguous evidence were considered insufficient to indict sugar as a dietary evil—innocent until proven guilty. These two reports also reviewed the dietary fat/heart-disease connection, which also constituted a collection of inconclusive studies and ambiguous evidence. Here, though, dietary fat was assumed guilty until proved innocent. And so the existence of ambiguous evidence was considered sufficient reason to condemn fat in the diet, particularly saturated fat, while the existence of ambiguous evidence was simultaneously considered reason enough to exonerate sugar.