(CNN) An old study is now shedding new light on the sugar industry's controversial past, and its secrets are being revealed in a new paper.

The 1960s study, which suggests a link between a high-sugar diet and high blood cholesterol levels and cancer in rats, was sponsored by the sugar industry, according to the perspective paper published in the journal PLOS Biology on Tuesday.

Yet the study itself was never published and has been forgotten until now.

"All we know is that the plug got pulled and nothing got published," said Stanton Glantz, a professor of medicine at the University of California, San Francisco and a co-author of the new paper.

"Whether the investigator didn't bother to try or whether he tried and failed, we don't know. Or whether there was some kind of clause in his agreement with the sugar people that precluded him from publishing, we don't know," he said.

This enigmatic study seems to provide evidence of the harmful health impacts of eating too much sugar. It also suggests that a group then called the Sugar Research Foundation might have manipulated scientific research in its favor, according to the new paper.

The authors of the new paper previously conducted a separate historical analysis of sugar industry-related documents and studies.

That analysis, published last year in JAMA Internal Medicine , suggested that the Sugar Research Foundation sponsored a research program that successfully cast doubt about the health hazards of a high-sugar diet and rather promoted fat "as the dietary culprit" in health concerns such as heart disease.

"The kind of science manipulation that the tobacco industry engaged in is exactly the same kind of behavior that we've documented in these papers from the sugar industry," said Glantz, who has also studied the tobacco industry

How a forgotten study gets found

The foundation, now called the Sugar Association , spoke out against that analysis last year and has contested the new PLOS Biology paper, telling CNN that it's "not actually a study, but a perspective: a collection of speculations and assumptions about events that happened nearly five decades ago, conducted by a group of researchers and funded by individuals and organizations that are known critics of the sugar industry."

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The association also noted that the study described in the new paper ended without publication partly due to being "significantly delayed" and "consequently over budget."

"We don't know what would have happened had this study come out differently and showed no effect of sugar," Glantz said. "I would bet that it would have been published, and they would be thumping the drums about it."

Cristin Kearns, an assistant professor at the UCSF School of Dentistry and lead author of the paper, said she learned about the long-lost study while collecting and analyzing letters between executives at the Sugar Research Foundation and various scientists from 1959 to 1971.

Then she noticed that the study was mentioned in a separate book that was published by the Sugar Research Foundation, which she found in a public library.

Photos: How much sugar is your kid eating? Photos: How much sugar is your kid eating? We took the most popular food brands among Americans, in nine categories young kids love, and used the current US dietary guidelines to illustrate what the daily recommended amount of sugar for kids looks like. Our math: Each of these images represents 33 grams of sugar. The recommendation is that added sugar should equal less than 10% of one's daily caloric needs. The median calories for moderately active 4- to 8-year-olds is 1,500 calories. So we calculated 9% of 1,500 as 135 calories, which equals 33 grams of sugar per day. If your child consumes what is pictured, they will probably have maxed out their recommended sugar intake for the whole day. Hide Caption 1 of 10 Photos: How much sugar is your kid eating? For a standard 12-ounce can of Coca-Cola, about four-fifths of the can equals 33 grams of sugar. Hide Caption 2 of 10 Photos: How much sugar is your kid eating? For a standard 6-ounce container of Yoplait yogurt (strawberry), one plus four-fifths of another equals 33 grams of sugar. Hide Caption 3 of 10 Photos: How much sugar is your kid eating? For a 20-ounce bottle of Gatorade, there are 33 grams of sugar in about 97% of the bottle. Hide Caption 4 of 10 Photos: How much sugar is your kid eating? For an 8-ounce bottle of Nesquik low-fat chocolate milk, one and a half bottles equals 33 grams of sugar. Hide Caption 5 of 10 Photos: How much sugar is your kid eating? For a 6.75-ounce carton of Mott's apple juice, one plus another two-fifths of a carton equals 33 grams of sugar. Hide Caption 6 of 10 Photos: How much sugar is your kid eating? For a 0.9 oz bag of Welch's Mixed Fruit snacks, there are 33 grams of sugar in three bags. Hide Caption 7 of 10 Photos: How much sugar is your kid eating? For Chips Ahoy chocolate chip cookies, nine cookies equal 33 grams of sugar. Hide Caption 8 of 10 Photos: How much sugar is your kid eating? For Honey Nut Cheerios, three plus two-thirds servings equals 33 grams of sugar. (One serving is three-quarters of a cup.) Hide Caption 9 of 10 Photos: How much sugar is your kid eating? For a standard 52.7-gram Snickers, one plus one-fifth of a bar equals 33 grams of sugar. Hide Caption 10 of 10

The book "listed all of their research projects between 1943 and 1972, and this project was listed in their report," Kearns said. "This particular project didn't have any publications, and so that made me curious about wanting to understand more about the project."

The study was called Project 259 , and the Sugar Research Foundation initially authorized 15 months of funding for it from June 1968 to September 1969, according to the paper.

As Kearns learned more about Project 259, she discovered that the study resulted in two findings in rats that, had funding been extended, would have been unfavorable to the sugar industry's commercial interests, according to the paper.

The 'fascinating' findings

First, the study showed that the urine of rats fed a high-sugar diet appeared to have higher levels of an enzyme called beta-glucuronidase than the urine of rats fed a basic diet high in starch, according to the paper.

"That was of some policy relevance at the time, because there was something called the Delaney clause , which said the FDA was supposed to keep carcinogens out of the food supply even if they were animal carcinogens," Glantz said.

Project 259 also showed a statistically significant decrease in triglycerides , a type of fat in blood, in rats that were fed a high-sugar diet and were stripped of bacteria in their guts, compared with conventional rats fed a basic diet. Colonies of bacteria in your gut are known as the gut microbiome.

Photos: How many calories are in your sweetener? Photos: How many calories are in your sweetener? The sweet truth – Natural and artificial sweeteners are in more food products than you might expect. Find out how many calories are in your favorite sweetener and see which ones have the most nutritional bang for your buck. Hide Caption 1 of 10 Photos: How many calories are in your sweetener? White sugar – What most people consider sugar is refined granulated sugar , or white sugar, which is derived from sugarcane or sugar beets. Common in foods, it has less nutrients than other natural sweeteners due to a refining process. Calories per tablespoon: 48. Hide Caption 2 of 10 Photos: How many calories are in your sweetener? Brown sugar – Brown sugar is created when molasses is added to sugar crystals. It has higher calcium and potassium levels than its white counterpart. The darker the sugar, the more molasses is present. Calories per tablespoon: 51. Hide Caption 3 of 10 Photos: How many calories are in your sweetener? Molasses – Molasses is a byproduct when sugarcane and sugar beets are refined. It is often used in baked goods, and is a rock star when it comes to nutrition with 1,464 mg of potassium, 205 mg of calcium and 242 mg of magnesium -- the highest of all the sweeteners. Calories per tablespoon: 58. Hide Caption 4 of 10 Photos: How many calories are in your sweetener? Maple syrup – Maple syrup is made from the sap of maple trees, though the artificial varieties are often just a combination of water and sugars. Nutritional perks of authentic syrups include calcium and potassium. Calories per tablespoon: 52. Hide Caption 5 of 10 Photos: How many calories are in your sweetener? Honey – Honey is produced by bees and has the most calories out of all the sweeteners on our list. The Mayo Clinic recommends that people who have bee-related allergies avoid honey, and it shouldn't be given to children younger than 12 months. Calories per tablespoon: 64. Hide Caption 6 of 10 Photos: How many calories are in your sweetener? Corn Syrup – Corn syrup is a sweetener made from corn starch that is commonly used in drinks and packaged foods. It comes in light, dark and high-fructose syrups (the dark syrup contains the most nutrients). Mayo Clinic says there is a lack of evidence on the possible dangers of the controversial high-fructose variety. Calories per tablespoon: Light (62), dark (57), high-fructose (53). Hide Caption 7 of 10 Photos: How many calories are in your sweetener? Agave nectar – A more exotic sweetener, agave nectar is created from the agave plant that is native to southern and western United States and parts of South America. It contains fewer carbs than most other sweeteners and contains vitamin C. Calories per tablespoon: 63. Hide Caption 8 of 10 Photos: How many calories are in your sweetener? Stevia – The leaves from stevia plants are used for medicinal purposes and as a sugar-free sweetener. It is reported to be much sweeter than white sugar, but isn't approved by the FDA . Nausea is a possible side effect . Calories per tablespoon: 0. Hide Caption 9 of 10 Photos: How many calories are in your sweetener? Artificial sweeteners – Equal and NutraSweet are FDA-approved artificial sweeteners made from aspartame (two amino acids put together). Another artificial sweetener, Splenda , is sucralose-based and is created from chemically processed sugar. According to researchers , one possible risk of digesting these products is that it can confuse your body, making it harder to process real sugars as a result. Calories per tablespoon: 0. Hide Caption 10 of 10

"Basically, they found that to get that elevated triglyceride response in the blood in rats that were fed a high-sugar diet, there needed to be bacteria in the gut," Kearns said.

"So without the bacteria, you didn't get the high triglyceride response, and so this proved to them at the time that the gut microbiome had a role in this elevated triglyceride response to eating sugar," she said. "I thought this is a fascinating study that they were even considering the role of the gut microbiome back as far as the 1960s."

Yet a limitation of the new paper is that it turns the spotlight on an animal study, and how sugar impacts rats may not exactly mirror how it could impact humans.

On the other hand, "I think doing animal studies is an important way to help understand the mechanisms of disease," Kearns said. "While obviously, a rat is not exactly the same as a human, it allows you to conduct experiments in a certain way to learn things that can influence future studies."

The sugar industry responds

In its written statement to CNN, the Sugar Association noted that the authors of the new paper did not reach out to it to verify any of their claims.

"We reviewed our research archives and found documentation that the study in question ended for three reasons, none of which involved potential research findings: the study was significantly delayed; it was consequently over budget; and the delay overlapped with an organizational restructuring with the Sugar Research Foundation becoming a new entity, the International Sugar Research Foundation," the association's statement said.

"There were plans to continue the study with funding from the British Nutrition Foundation, but, for reasons unbeknown to us, this did not occur," the statement said.

In response, Kearns pointed out that other studies that overlapped with that organizational restructuring were still continued.

The Sugar Association's statement added that sugar consumed in moderation can be part of a balanced lifestyle and that the association remains committed to supporting research to further understand the role sugar plays in consumers' diets.

Why the timing is 'concerning'

All in all, the new paper's findings were "striking" and "ethically concerning" to Dr. Sanjay Basu, an assistant professor of medicine at Stanford University who was not involved in the work.

"The context for this historically is that during the time at which these studies were taking place, a lot of dietary recommendations were being formulated that emphasized reducing high-fat foods in particular, and in many cases low-fat foods were replaced by high-sugar foods to be more palatable," said Basu, who has studied the health impacts of added sugars in his own research.

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"The fact that sugar was not being considered an additionally concerning substance unfortunately led to a lot of changes in the American diet that correspond to a rise in obesity and type 2 diabetes," Basu said.

"So the suppression of this type of study is partly greatly concerning because of the time in which it took place," he said. "Although we're not sure what a safe amount of added sugar is, it's pretty clear and increasingly apparent that we're well above what might be considered reasonable in terms of our added sugar consumption as a country."