A leading U.S. sugar industry research group may have called off a study that linked sugar to negative health effects five decades ago, a recent review from the University of California at San Francisco (UCSF) has found.

In a paper published on Nov. 21 in the open access journal PLOS Biology, UCSF researchers reviewed internal documents from the U.S. sugar industry. Scientists Cristin Kearns, Dorie Apollonio and Stanton Glantz found that the International Sugar Research Foundation (ISRF), now known as the Sugar Association, funded animal testing to assess the effects of sucrose on the cardiovascular system nearly 50 years ago.

According to the researchers, when the ISRF’s study suggested a connection between sucrose and heart disease and bladder cancer, the foundation cancelled the project without making its findings public.

"The kind of manipulation of research is similar what the tobacco industry does," co-author Stanton Glantz said in a statement.

"This kind of behaviour calls into question sugar industry-funded studies as a reliable source of information for public policy making."

The ISRF began a study on rats called “Project 259” in 1968 “to measure the nutritional effects of the [bacterial] organisms in the intestinal tract,” the UCSF’s new study says. The ISRF’s research compared the nutritional effects of eating sucrose versus starch.

The study on rats suggested that gut bacteria helped moderate the negative effects of sugar on cardiovascular health, but it also indicated that sugar may increase the risk of bladder cancer.

The study also found that eating sucrose led to higher cholesterol levels than eating starch.

"This incidental finding of Project 259 demonstrated to ISRF that sucrose versus starch consumption caused different metabolic effects, and suggested that sucrose, by stimulating urinary beta-glucuronidase, may have a role in the pathogenesis of bladder cancer,” Kearns, Apollonio, and Glantz said in a statement.

In the 1960s, scientists disagreed about whether sugar could raise triglycerides (a type of fat found in the blood) in the same way that starch does. The UCSF researchers argue that Project 259 would’ve proven that sugar could in fact raise triglycerides.

"Our study contributes to a wider body of literature documenting industry manipulation of science," the researchers said in their study.

"Based on ISRF's interpretation of preliminary results, extending Project 259's funding would have been unfavorable to the sugar industry's commercial interests.”

In an internal document from 1969, the ISRF called the rat study “one of the first demonstrations of a biological difference between sucrose and starch fed rats,” the new UCSF study says.

But after learning more about the study’s findings, the ISRF cancelled funding for the project shortly before its completion date and failed to publish any of the findings. 

A previous analysis showed that the sugar industry funded research that cast doubt on sugar's role in heart disease, in part by pointing the finger at fat.