The revelations are important because the debate about the relative harms of sugar and saturated fat continues today, Dr. Glantz said. For many decades, health officials encouraged Americans to reduce their fat intake, which led many people to consume low-fat, high-sugar foods that some experts now blame for fueling the obesity crisis.

“It was a very smart thing the sugar industry did, because review papers, especially if you get them published in a very prominent journal, tend to shape the overall scientific discussion,” he said.

Dr. Hegsted used his research to influence the government’s dietary recommendations, which emphasized saturated fat as a driver of heart disease while largely characterizing sugar as empty calories linked to tooth decay. Today, the saturated fat warnings remain a cornerstone of the government’s dietary guidelines, though in recent years the American Heart Association, the World Health Organization and other health authorities have also begun to warn that too much added sugar may increase cardiovascular disease risk.

Marion Nestle, a professor of nutrition, food studies and public health at New York University, wrote an editorial accompanying the new paper in which she said the documents provided “compelling evidence” that the sugar industry had initiated research “expressly to exonerate sugar as a major risk factor for coronary heart disease.”

“I think it’s appalling,” she said. “You just never see examples that are this blatant.”

Dr. Walter Willett, chairman of the nutrition department at the Harvard T. H. Chan School of Public Health, said that academic conflict-of-interest rules had changed significantly since the 1960s, but that the industry papers were a reminder of “why research should be supported by public funding rather than depending on industry funding.”

Dr. Willett said the researchers had limited data to assess the relative risks of sugar and fat. “Given the data that we have today, we have shown the refined carbohydrates and especially sugar-sweetened beverages are risk factors for cardiovascular disease, but that the type of dietary fat is also very important,” he said.

The JAMA Internal Medicine paper relied on thousands of pages of correspondence and other documents that Cristin E. Kearns, a postdoctoral fellow at U.C.S.F., discovered in archives at Harvard, the University of Illinois and other libraries.