(CNN) Private emails between employees at the Coca-Cola Co. and the US Centers for Disease Control and Prevention have been exposed in a new research paper, raising questions about just how extensive of a relationship the soda company has had with the nation's public health agency.

The paper, published Tuesday in the journal The Milbank Quarterly includes excerpts from emails and suggests that current and former Coca-Cola staff tried to influence the CDC by attempting to frame the debate around whether sugar-sweetened beverages play a role in America's obesity epidemic, as well as trying to lobby decision-makers.

The email exchanges -- obtained through Freedom of Information Act requests -- were sent between 2011 and the time the FOIA requests were made in 2016 and 2017.

The main concern behind Coca-Cola and CDC partnerships would be that the soda company may try to downplay how some of its sweetened soda products are leading sources of added sugar in the American diet . Frequently sipping sugary beverages is associated with a higher risk of obesity, Type 2 diabetes, heart disease and tooth decay, among other health concerns.

Separate research has shown that such manufacturers have used front groups, lobbying and other tactics to shift focus away from their products and to prevent measures such as sugar taxes that could damage their profit, said Nason Maani Hessari, a research fellow in the Department of Health Services Research and Policy at the London School of Hygiene & Tropical Medicine in the United Kingdom, who was first author of the new paper.

Now, "these email exchanges show what appear to be attempts to leverage personal relationships at the CDC to further these goals at the expense of population health -- and lead to questions about whether organizations like the CDC should refrain from engaging in partnerships where there is such a potential for conflict of interest," he said.

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Meanwhile, the Coca-Cola Co. published a website in 2015 that details its partnerships in an effort to remain fully transparent with the public about its relationships.

In 2016, the company implemented new principles related to its involvement in public health, including that it will no longer provide all of the funding for scientific research or be the sole provider of funding for programs that engage the health professional community.

In response to the new paper, the Coca-Cola Co. said in a statement Monday that over the past four years, it "has been on a journey to be a more helpful and effective partner in efforts to address the issue of obesity."

"We've listened closely to those in the public health community and other stakeholders to better understand the most appropriate role we can play to support the fight against obesity in a way that is credible, transparent, and beneficial for everyone and we have evolved our approach," the statement said. "We recognize that too much sugar isn't good for anyone. In fact, we support the current recommendation by several leading health authorities, including the World Health Organization , that people should limit their intake of added sugar to no more than 10% of their total energy/calorie consumption."

Conversations between CDC and Coke

For the new paper, researchers sent 10 requests through the Freedom of Information Act to gain access to email exchanges between Coca-Cola and the CDC.

Of those requests, five were rejected as "too broad" or yielded no records, and three are pending. One of the rejected requests was repeated and is pending, so it falls within both categories.

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The remaining three requests uncovered 295 pages of communications from 86 emails.

Based on the email exchanges, at least one visit was arranged for CDC staff to Coca-Cola's headquarters, the researchers found.

Another email exchange showed that former Coca-Cola executive Alex Malaspina wrote to former CDC official Dr. Barbara Bowman about concerns that WHO's then-director-general Dr. Margaret Chan back restrictions on the consumption of sugary soft drinks, such as in the form of soda taxes. This exchange, which happened in June 2015, had been reported in the media, Maani Hessari said.

"Any ideas on how to have a conversation with WHO? Now, they do not want to work with industry. Who finds all the new drugs? Not WHO, but industry. She is influenced by the Chinese Govt [sic] and is against US. Something must be done," the email said in part, according to the paper's findings.

Bowman, former director of CDC's Division for Heart Disease and Stroke Prevention, responded that day, suggesting some contacts who may have close connections with WHO regional offices, including Bill Gates.

"The Malaspina-Bowman exchanges had been previously reported in the media, and so we knew there was some contact between the two," Maani Hessari said. "Having said that, I was surprised by the familiarity between the participants in the emails."

In 2016, Bowman resigned from the CDC.

The new paper had some limitations, including that the research relies solely on the FOIA requests and that broader communications between CDC staff and Coca-Cola, such as phone calls or in-person meetings, are not included in the data. Coca-Cola's headquarters and the CDC are both in Atlanta.

Additionally, the sample size of emails is small, and some FOIA requests are pending.

In its statement, Coca-Cola noted, "We are rethinking many of our recipes around the world to reduce sugar, and we are exploring and bringing to market new sugar alternatives that help us keep the great tastes people love, but with less sugar and fewer calories."

'Frankly, it's a little bit scary'

This isn't the first time soda companies and other industries have been found to have had controversial relationships with government agencies or public health groups.

A historical analysis published in the journal JAMA Internal Medicine in 2016 claimed that the sugar industry sponsored research that cast doubt about sugar's health risks and promoted fat "as the dietary culprit" in heart disease -- and didn't disclose it.

Another paper, published in the American Journal of Preventive Medicine in 2016, found that Coca-Cola and PepsiCo sponsored at least 96 national health organizations at the same time the companies were lobbying against public health bills intended to reduce how many sugary sodas people drink.

The sponsorships could have influenced the health groups' support of various public health measures intended to reduce obesity by limiting soda consumption, according to Dr. Michael Siegel, professor of community health sciences in the Boston University School of Public Health , who was a co-author of that paper.

Another example, Siegel said, is how the National Institute on Alcohol Abuse and Alcoholism came under scrutiny over communications with the alcohol industry last year.

As for the new paper that highlights Coca-Cola emails, "frankly, it's a little bit scary to see the degree to which there is collaboration and partnerships between the CDC and this corporation," said Siegel, who was not involved in the paper.

"To me, the most disturbing aspect was the extent to which CDC officials were actually helping the company achieve its lobbying objective, and there were examples of giving them advice, providing contact information, helping them to try to fight against soda taxes," he said. "The larger implications of this, in my view, are that it really highlights the need to put up barrier walls -- talking about building walls -- but we need to have some barrier walls built between our government agencies and these corporations to prevent undue influence from occurring."

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Coca-Cola's possible influence on certain health agencies seems to go beyond the United States and can be seen in other countries, according to Susan Greenhalgh, a research professor of Chinese society at Harvard University , who was not involved in the new paper.

The new paper features some of the same actors as those in Greenhalgh's research on China, through which she found that Coca-Cola may have worked through the industry-funded nonprofit International Life Sciences Institute to encourage an emphasis on links between exercise and obesity over links between diet and obesity.

In other words, Greenhalgh's work explores the political dynamics by which Coca-Cola, working through a nonprofit, "managed to actually redirect China's science and policy on obesity and related chronic diseases to align with Coke's position that when it comes to obesity, it is physical activity, not food and drink, that matter," she said, adding that's a position few experts accept.

"It shows not just the attempt to influence but also the actual impact," she said.

Where Coke is more readily available than water

The new paper's findings were not surprising to Laura Mebert, assistant professor of social science at Kettering University in Michigan, because "we've known for a long time through other means that industries do this."

Yet as access to sugar-sweetened beverages continues to grow globally, the potential public health impacts remain important.

For instance, "it is true that Coca-Cola is more readily available than potable water in some parts of the world," said Mebert, who was not involved in the new paper but has conducted separate research in San Cristóbal de las Casas , a town in Chiapas, Mexico, between 2007 and 2008.

"In some neighborhoods households only had running water for a few hours per week, and in any case, it had to be boiled before it was drinkable," Mebert said.

"However, Coca-Cola and other bottled drinks were available for purchase in every convenience store. Meanwhile, the Mexican government charges the Coca-Cola bottling plant in San Cristóbal far less for clean water than the local government charges the average household," she said. "This isn't just a Mexican problem. The same is true in my hometown of Flint, Michigan, where households are charged some of the highest monthly water rates in the country."

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Mebert said, "In both Mexico and the US, the inequity between companies' and households' access to water is a problem created by industry but allowed by government."